Contents:

Preface ... 4
Introduction ... 5
Origin of the Hawaiian Islands ... 7
Hawaiian Eruptions in Recorded History ... 13
Volcano Monitoring and Research ... 16
Kilauea's Volcanic "Plumbing System" ... 24
Eruptive Style: Powerful but Usually Benign ... 26
Hawaiian Volcanic Products, Landforms, and Structures ... 37
Loihi: Hawaii's Newest Volcano ... 45
Volcanic Hazards and Benefits ... 47
Selected Readings ... 52
Selected Viewings ... 53
Endnotes ...55 



Page 4

[image caption: Lava shoots 1,000 feet into the air during a high-
fountaining episode of the 1983-to-present Pu'u 'O'o eruption of Kilauea 
Volcano. (Photograph by J.D. Griggs.)]


Preface

Viewing an erupting volcano is a memorable experience, one that has 
inspired fear, superstition, worship, curiosity, and fascination 
throughout the history of mankind. In modern times, volcanic phenomena 
have attracted intense scientific interest, because they provide the key 
to understanding processes that have created and shaped more than 80 
percent of the Earth's surface. The active Hawaiian volcanoes have 
received special attention worldwide because of their frequent spectacular 
eruptions, which can be viewed and studied with relative ease and safety. 
In January 1987, the Hawaiian Volcano Observatory (HVO), located on the 
rim of Kilauea Volcano, celebrated its 75th Anniversary. In honor of HVO's 
Diamond Jubilee, the U.S. Geological Survey (USGS) published Professional 
Paper 1350, an up-to-date summary of the many studies on Hawaiian 
volcanism by the USGS and other scientists. Drawing from the wealth of 
data contained in that volume, this booklet focuses on selected aspects of 
the eruptive history, style, and products of two of Hawaii's active 
volcanoes, Kilauea and Mauna Loa. This general-interest booklet is a 
companion to the one on Mount St. Helens Volcano published in 1984. 
Together, these works illustrate the contrast between the two main types 
of volcanoes: shield volcanoes, such as those in Hawaii, which are 
typically nonexplosive; and composite volcanoes, such as Mount St. Helens 
in the Cascade Range, which are renowned for their explosive eruptions. 

Page 5

Introduction

"The loveliest fleet of islands that lies anchored in any ocean."
 --Mark Twain 

Few would quarrel with Mark Twain's vivid description of Hawaii, written 
after his 4-month stay in 1866. The Hawaiian Islands were discovered and 
settled around the 6th century A.D. by Polynesians sailing from islands, 
probably the Marquesas, in the southern tropical Pacific. Subsequently, a 
thousand years or more of cultural isolation passed before Hawaii was 
first visited by non-Polynesians. On January 18, 1778, during his third 
major voyage in the Pacific, the famous British navigator and explorer, 
Captain James Cook, sighted the Polynesians' secluded home.  Cook named 
his discovery the "Sandwich Islands," in honor of the Earl of Sandwich, 
then First Lord of the British Admiralty. Mark Twain's fleet of islands is 
larger than Rhode Island and Connecticut combined. The island of Hawaii, 
commonly called the "Big Island," covers more than twice the total area of 
the other islands.

Hawaii, which became our 50th state in 1959, is now home for more than one 
million people and hosts many times that number of visitors each year. 

[image (map) caption: The principal Hawaiian islands (all capital letters) 
are the exposed tops of volcanoes that rise tens of thousands of feet 
above the ocean floor. Some islands are made up of two or more volcanoes. 
Loihi Seamount, Hawaii's newest volcano, still lies about 3,100 feet 
beneath the sea. (Modified by permission from a map published by Dynamic 
Graphics, Inc., Berkeley, California.)]

Page 6

[image caption: Sketch map of the southeastern part of the island of 
Hawaii and adjacent offshore, showing the principal features and 
localities of Mauna Loa, Kilauea, and Loihi Volcanoes discussed in the 
text.]

Hawaii's worldwide image as an idyllic tropical paradise is well deserved. 
What is less well-known, however, is that the islands exist only because 
of nearly continuous volcanic activity. All of the prominent features of 
the Hawaiian Islands, such as Diamond Head on Oahu, Haleakala Crater on 
Maui, and the huge masses of Mauna Loa and Mauna Kea on the Big Island, 
are volcanic.

Since the beginning of a historical record early in the 19th century, 
eruptions have occurred frequently at Mauna Loa and Kilauea; these two 
volcanoes on the Big Island are among the most active in the world. Nearby 
Loihi Seamount, off the Big Island's south coast, is the newest Hawaiian 
volcano, not yet visible above the ocean surface. 

Most eruptions of Mauna Loa and Kilauea are nonexplosive, and both 
volcanoes are readily accessible; scientists can study them at close range 
in relative safety. As a result, these are two of the most intensely 
observed and best understood volcanoes on our planet. Research on these 
active volcanoes provides a basis for understanding the life story of 
older, now inactive Hawaiian volcanoes and similar volcanoes worldwide. 
Hawaii serves as a superb natural laboratory for the study of volcanic 
eruptions. 

[image caption: Liliuokalani Park, in the city of Hilo on the Big Island, 
typifies the tropical beauty and serenity of the Hawaiian Islands. 
(Photograph by John Penisten, Hilo, Hawaii.)]

Page 7

Origin of the Hawaiian Islands

The Hawaiian Islands are the tops of gigantic volcanic mountains formed by 
countless eruptions of fluid lava(1) over several million years; some 
tower more than 30,000 feet above the sea floor.(2) These volcanic peaks 
rising above the ocean surface represent only the tiny, visible part of an 
immense submarine ridge, the Hawaiian Ridge--Emperor Seamount Chain, 
composed of more than 80 large volcanoes. This range stretches across the 
Pacific sea floor from the Hawaiian Islands to the Aleutian Trench. The 
length of the Hawaiian Ridge segment alone, between the Big Island and 
Midway Island to the northwest, is about 1,600 miles, roughly the distance 
from Washington, D.C., to Denver, Colorado. The amount of lava erupted to 
form this huge ridge, about 186,000 cubic miles, is more than enough to 
cover the State of California with a mile-thick layer. 

(1) Scientists use the term lava for molten rock (and contained gases) 
that breaks through the Earth's surface, and the term magma for the molten 
rock underground. 
(2) The United States uses English units of measurements. For readers in 
the many countries that use metric units, a conversion table is given in 
the back of the booklet. 

[image caption: Map of the Pacific basin showing the location of the 
Hawaiian Ridge-Emperor Seamount Chain in relation to some other features 
and localities mentioned in the text. (Base map reprinted by permission 
from World Ocean Floor Panorama by Bruce C. Heezen and Marie Tharp, 
Copyright 1977.)]

Page 8

Hawaiian Legends and Early Scientific Work

The distinctive northwest-southeast alignment of the Hawaiian chain was 
known to early explorers of the Pacific Ocean, including the Polynesians 
who first settled the islands. The ancient Hawaiians were superb sailors, 
excellent navigators, and keen observers of nature, including volcanic 
eruptions and their effects. They noticed the extent of erosion from 
island to island, the amount of vegetation on the slopes of the various 
volcanoes, the freshness of lava flows, and other indicators of the 
relative ages of the islands. The legends of the early Hawaiians clearly 
reveal that they recognized that the islands are progressively younger 
from the northwest to the southeast. 

Hawaiian legends tell that eruptions were caused by Pele, the beautiful 
but tempestuous Goddess of Volcanoes, during her frequent moments of 
anger. Pele was both revered and feared; her immense power and many 
adventures figured prominently in ancient Hawaiian songs and chants. She 
could cause earthquakes by stamping her feet and volcanic eruptions and 
fiery devastation by digging with the Pa'oa, her magic stick. An oft-told 
legend describes the long and bitter quarrel between Pele and her older 
sister Namakaokahai that led to the creation of the chain of volcanoes 
that form the islands. 

[image caption: Above: Pele, the Goddess of Volcanoes, as portrayed by 
artist D. Howard Hitchcock. (Photograph by J.D. Griggs with permission of 
the Volcano House Hotel, owner of the original painting.) Below: Night 
view (time exposure) of Pele's home during the 1967-68 eruption within 
Halemaumau Crater. (Photograph by Richard S. Fiske.)]

Page 9

Pele first used her Pa'oa on Kauai, where she subsequently was attacked by 
Namakaokahai and left for dead. Recovering, she fled to Oahu, where she 
dug a number of "fire pits," including the crater we now call Diamond 
Head, the tourist's landmark of modern Honolulu. Pele then left her mark 
on the island of Molokai before traveling further southeast to Maui and 
creating Haleakala Volcano, which forms the eastern half of that island. 
By then Namakaokahai realized that Pele was still alive and went to Maui 
to do battle with her. After a terrific fight, Namakaokahai again believed 
that she had killed her younger sister, only to discover later, however, 
that Pele was very much alive and busily working at Mauna Loa Volcano on 
the island of Hawaii. Namakaokahai then conceded that she could never 
permanently crush her sister's indomitable spirit and gave up the 
struggle. Pele dug her final and eternal fire pit, Halemaumau Crater, at 
the summit of Kilauea Volcano, where she is said to reside to this day. 
The migration of volcanic activity from Kauai to Hawaii described by this 
Hawaiian legend is confirmed by modern scientific studies. 

The first geologic study of the Hawaiian Islands was conducted during 6 
months in 1840-1841, as part of the U.S. Exploring Expedition of 1838-
1842, commanded by Lieutenant Charles Wilkes of the U.S. Navy.

The expedition's geological investigations were directed by James Dwight 
Dana. Though only 25 years old in 1838, Dana was no stranger to volcanoes. 
In 1834 he had studied Vesuvius, the active volcano near Naples, Italy. 

Dana and his colleagues recognized that the islands become increasingly 
younger from northwest to southeast along the Hawaiian volcanic chain, 
largely because of differences in their degree of erosion. The longer the 
length of time since its last eruption, the greater the erosion of the 
volcano. He also suggested that some other island chains in the Pacific 
showed a similar general decrease in age from northwest to southeast. 

The alignment of the Hawaiian Islands, Dana proposed, reflected localized 
volcanic activity along segments of a major fissure zone slashing across 
the ocean floor. Dana's "great fissure" origin for the islands served as a 
prominent working hypothesis for many subsequent studies until the mid-
20th century. The monumental work of Dana -- considered to be the first 
American volcanologist -- resulted in greatly increased awareness of the 
Hawaiian volcanoes, which continue to attract much scientific attention. 

[image caption: Deeply eroded Koolau Volcano (left photograph), island of 
Oahu, is 2 to 3 million years older than Mauna Loa Volcano (right 
photograph), on the Big Island, which is unscarred by erosion. Snow-capped 
Mauna Loa is viewed from the east, and the Hawaiian Volcano Observatory 
(circled) can be seen on the west rim of Kilauea's summit crater 
foreground). (Photographs by Richard S. Fiske.)]

Page 10

[map of] Active volcanoes of the world

[image caption: Most active volcanoes are located along or near the 
boundaries of the Earth's shifting tectonic plates. Hawaiian volcanoes, 
however, occur in the middle of the Pacific Plate. Not all of the Earth's 
more than 500 active volcanoes are shown.]

Page 11

Plate Tectonics and the Hawaiian "Hot Spot"

In the early 1960's, the related concepts of "seafloor spreading" and 
"plate tectonics" emerged as powerful new hypotheses that geologists used 
to interpret the features and movements of the Earth's surface layer. 
According to the plate-tectonics theory, the Earth's surface consists of 
about a dozen rigid slabs or plates, each averaging at least 50 miles 
thick. These plates move relative to one another at average speeds of a 
few inches per year--about as fast as human fingernails grow. Scientists 
recognize three common types of boundaries between these moving plates: 

(1) Divergent or spreading--adjacent plates pull apart, such as at the Mid-
Atlantic Ridge, which separates the North and South American Plates from 
the Eurasian and African Plates. This pulling apart causes "sea-floor 
spreading" as new material is added to the oceanic plates. 

(2) Convergent--plates moving in opposite directions meet and one is 
dragged down (or subducted) beneath the other. Convergent plate boundaries 
are also called subduction zones and are typified by the Aleutian Trench, 
where the Pacific Plate is being subducted under the North American Plate. 

(3) Transform fault--one plate slides horizontally past another. The best 
known example is the earthquake-prone San Andreas fault zone of 
California, which marks the boundary between the Pacific and North 
American Plates. 

The great majority of the world's earthquakes and active volcanoes occur 
near the boundaries of the Earth's shifting plates. Why then are the 
Hawaiian volcanoes located near the middle of the Pacific Plate, more than 
2,000 miles from the nearest plate boundary? In 1963, J. Tuzo Wilson, a 
Canadian geophysicist, provided an ingenious explanation within the 
framework of plate tectonics by proposing the "Hot Spot" hypothesis. 
Wilson's hypothesis has come to be accepted widely, because it agrees well 
with much of the scientific data on the Pacific Ocean in general, and the 
Hawaiian Islands in particular.
 
According to Wilson, the distinctive linear shape of the Hawaiian-Emperor 
Chain reflects the progressive movement of the Pacific Plate over a deep 
immobile hot spot. This hot spot partly melts the region just below the 
overriding Pacific Plate, producing small, isolated blobs of magma. Less 
dense than the surrounding solid rock, the magma rises buoyantly through 
structurally weak zones and ultimately erupts as lava onto the ocean floor 
to form volcanoes. 

Over a span of about 70 million years, the combined processes of magma 
formation, eruption, and continuous movement of the Pacific Plate over the 
stationary hot spot have left the trail of volcanoes across the ocean 
floor that we now call the Hawaiian-Emperor Chain. Scientists interpret 
the sharp bend in the chain, about 2,200 miles northwest of the Big 
Island, as indicating a change in the direction of plate motion that 
occurred about 43 million years ago, as suggested by the ages of the 
volcanoes bracketing the bend. 

Part of the Big Island, the south-easternmost and youngest island, 
presently overlies the hot spot and still taps the magma source to feed 
its two currently active volcanoes, Kilauea and Mauna Loa. The active 
submarine volcano Loihi, off the Big Island's south coast, may mark the 
beginning of the zone of magma formation at the southeastern edge of the 
hot spot. The other Hawaiian islands have moved northwestward beyond the 
hot spot, were successively cut off from the sustaining magma source, and 
are no longer volcanically active. 

Page 12

[image caption: Artist's conception of the northwestward movement of the 
Pacific Plate over the fixed Hawaiian "Hot Spot" to illustrate the 
formation of the Hawaiian Ridge-Emperor Seamount Chain. (Modified from a 
drawing provided by Maurice Krafft, Centre de Volcanologie, Cernay, 
France.)]

The progressive northwesterly drift of the islands from their point of 
origin over the hot spot is well shown by the ages of the principal lava 
flows on the various Hawaiian Islands from northwest (oldest) to southeast 
(youngest), given in millions of years: Kauai, 5.6 to 3.8; Oahu, 3.4 to 
2.2; Molokai, 1.8 to 1.3; Maui, 1.3 to 0.8; and Hawaii, less than 0.7 and 
still growing.

Even on the Big Island alone, the relative ages of its five volcanoes are 
compatible with the hot-spot theory. Kohala, at the northwestern corner of 
the island, is the oldest, having ceased eruptive activity about 60,000 
years ago. The second oldest is Mauna Kea, which last erupted about 3,000 
years ago; next is Hualalai, which has had only one historic eruption 
(1800-1801), and, lastly, both Mauna Loa and Kilauea have been vigorously 
and repeatedly active in historic times. Because it is growing on the 
southeastern flank of Mauna Loa, Kilauea is believed to be younger than 
its huge neighbor. 

The size of the Hawaiian hot spot is not known precisely, but it 
presumably is large enough to encompass the currently active volcanoes of 
Mauna Loa, Kilauea, Loihi and, possibly, also Hualalai and Haleakala. Some 
scientists have estimated the Hawaiian hot spot to be about 200 miles 
across, with much narrower vertical passageways that feed magma to the 
individual volcanoes.

Page 13

Hawaiian Eruptions in Recorded History

Hawaii has a brief written history, extending back only about 200 years, 
compared to such volcanic regions as Iceland, Indonesia, Italy, and Japan. 
Written accounts exist for most Hawaiian eruptions since 1820, when the 
first American missionaries settled in Hawaii. Descriptions of earlier 
eruptions are sketchier, because they are based only on interpretations of 
ancient Hawaiian chants and stories told by Hawaiian elders and early 
European residents to the American missionaries. 

All the known historic Hawaiian eruptions have been at Mauna Loa and 
Kilauea Volcanoes except for the following: the 1790? (year uncertain) 
eruption of Haleakala Volcano on Maui, and the 1800-1801 eruption of 
Hualalai Volcano, on the west coast of the Big Island. Although an 
exception to the overall northwest-southeast shift of volcanic activity, a 
series of submarine eruptions also probably occurred in 1955-56 between 
the islands of Oahu and Kauai and near Necker Island, about 350 miles 
northwest of Kauai.

[image caption: On March 30, 1984, both Kilauea and Mauna Loa were in 
simultaneous eruption, the first time since 1924. Kilauea's Pu'u 'O'o 
eruption began its 17th high-fountaining episode since January 1983 (above 
photograph by Kepa Maly, National Park Service) and a Mauna Loa eruption, 
which began on March 25, continued to feed a major lava flow that advanced 
toward the city of Hilo (bottom photograph by Scott Lopez, National Park 
Service.)]

Page 14

[image of graph showing] Hawaiian Eruptions in Recorded History

[image caption: Graph summarizing the eruptions of Mauna Loa and Kilauea 
Volcanoes in recorded history. Information is sketchy for historic 
eruptions before 1820, when the first American missionaries arrived in 
Hawaii. The total duration of eruptive activity in a given year, shown by 
the vertical bar, may be for a single eruption or combined for several 
separate eruptions.]

Page 15

[image caption: The active lava lake within Halemaumau Crater overflowing 
its levee, as painted by D. Howard Hitchcock in 1894. (Photograph by J.D. 
Griggs with permission of the Volcano House Hotel, owner of the original 
painting.)]

For the past 200 years, Mauna Loa and Kilauea have tended to erupt on 
average every two or three years, placing them among the most frequently 
active volcanoes of the world. Some intervals of repose between eruptions 
at a given volcano have been much longer than its long-term average. The 
individual Kilauea eruptions recorded historically are in addition to the 
nearly continuous eruptive activity within or near Halemaumau Crater, 
extending throughout the 19th century and into the early 20th century.

Simultaneous eruption of both volcanoes has been rare except at times when 
Kilauea was continuously active before 1924. The only post-1924 occurrence 
of simultaneous eruption was in March 1984, when activity at both 
volcanoes overlapped for one day. Long repose intervals for one volcano 
correlate approximately with increased activity at the other. This general 
relation is imperfect but holds well for post-1924 eruptive activity. 
Between 1934 and 1952, only Mauna Loa was active and, between 1952 and 
1974, only Kilauea was. 

Since July 1950, Hawaiian eruptive activity has been dominated by frequent 
and sometimes prolonged eruptions at Kilauea, while only two short-lived 
eruptions have occurred at Mauna Loa (July 1975 and March-April 1984). As 
of September 1986, Kilauea's eruption at Pu'u 'O'o, which began in January 
1983, shows no signs of decline. Except for the nearly continuous eruptive 
activity at Halemaumau for a century before 1924, and at Mauna Loa summit 
between 1872 and 1877, the Pu'u 'O'o eruption has now become the longest 
lasting single Hawaiian eruption in recorded history. 

A pattern of alternating dominant activity between Mauna Loa and Kilauea 
could imply that both volcanoes may alternately tap the same deep magma 
source. Whether this is so is a topic of scientific debate, because 
abundant chemical and physical evidence indicates that each volcano has 
its own shallow magma reservoir that operates independently of the other. 

The average volume of lava erupted at Kilauea Volcano since 1956 is 
between 110 and 130 million cubic yards per year. In contrast, the average 
rate of lava output along the entire Hawaiian-Emperor Chain during its 70-
million-year life is only about 20 million cubic yards per year. For 
reasons not yet understood, the rate of eruptive activity associated with 
the Hawaiian hot spot for the past few centuries appears exceptionally 
high relative to its long-term average.

[image (graph) caption: Brief high-fountaining episodes (shown by bars) 
alternated with longer intervals of low-level activity during the Pu'u 
'O'o eruption. Width of bar indicates duration of high fountaining.]

Page 16

Volcano Monitoring and Research

Before the 20th century, most scientific studies of volcanoes were 
conducted during short-lived expeditions, generally undertaken as a 
response to major eruptions. Thomas A. Jaggar, Jr., a geologist at the 
Massachusetts Institute of Technology (MIT), was not satisfied with that 
approach. He recognized that, to understand volcanoes fully, one must 
study them continuously before, during, and after eruptions. Jaggar's 
views were profoundly affected by a memorable visit in 1902 to the Island 
of Martinique (West Indies). He went as a member of the scientific 
expedition sent to study the catastrophic eruption of Mont Pelee that 
year, which devastated the city of St. Pierre and killed about 30,000 
people. 

In 1911, spurred by a stimulating lecture delivered by Jaggar, a group of 
Hawaiian residents founded the Hawaiian Volcano Research Association 
(HVRA). The logo of the HVRA included the motto Ne plus haustae aut 
obrutae urbes (No more shall the cities be destroyed), reflecting Jaggar's 
memory of Mont Pelee's destructive force and his optimistic belief that 
better understanding of volcanoes could reduce the hazard to life and 
property from eruptions. 

In 1912, with support from the HVRA and the Whitney Fund of MIT, Jaggar 
established the Hawaiian Volcano Observatory (HVO) to study the activity 
of Mauna Loa and Kilauea Volcanoes on a permanent, scientific basis. 
"Volcanology" emerged as a modern science with the founding of the HVO, 
which between 1912 and 1948 was managed by the HVRA, the U.S. Weather 
Bureau, the U.S. Geological Survey (USGS), and the National Park Service. 

[image caption: Above: The first Hawaiian Volcano Observatory (HVO), 
located near the site of the present Volcano House Hotel, as it appeared 
around 1922. (Photographer unknown; courtesy of the Bishop Museum, 
Honolulu, Hawaii.) Below: HVO at its present site, after the addition of a 
new wing (with observation tower) and renovation in 1986. (Photograph by 
J.D. Griggs.)]

Page 17

Since 1948, it has been been operated by the USGS. During the past 75 
years of research, HVO scientists have developed and refined most of the 
surveillance techniques now commonly employed by volcano observatories 
worldwide. 


Volcano monitoring

The term volcano monitoring refers to the observations and measurements 
scientists make to document changes in the state of the volcano during and 
between eruptions. Such changes are now well known for Kilauea, and a 
pattern of similar changes is becoming apparent for the less studied Mauna 
Loa. As magma enters the shallow summit reservoir, the volcano undergoes 
swelling or inflation (a process similar to the stretching of a balloon 
being filled with air). This swelling in turn causes changes in the shape 
of the volcano's surface. During inflation, the slope or tilt of the 
volcano increases, and reference points (benchmarks) on the volcano are 
uplifted relative to a stable point and move farther apart from one 
another. For Hawaiian volcanoes, pre-eruption inflation generally is slow 
and gradual, lasting for weeks to years. However, once eruption begins, 
the shrinking or deflation of the volcano typically occurs rapidly as 
pressure on the magma reservoir is relieved -- a process not unlike 
deflating a balloon. During deflation, changes in tilt and in vertical 
horizontal distances between benchmarks are opposite to those during 
inflation.

[image caption: Hypothetical cross section of Kilauea Volcano. Magma 
entering the shallow reservoir exerts pressure on the volcano, causing 
earthquakes and distorting its shape from the dotted-line profile to the 
solid-line profile. During inflation, reference points (benchmarks) on the 
volcano's surface are pushed upward and outward relative to points assumed 
to be stable. The changes in the volcano's shape and the occurrence of the 
earthquakes can be tracked precisely by volcano- monitoring techniques.]

Page 18

[image caption: Hawaiian Volcano Observatory (HVO) scientist using laser-
ranging instrument (left) to make electronic- distance measurement (EDM). 
(Photograph by Cristina Heliker.) The laser beam is reflected back to the 
EDM instrument by a cluster of retro-reflectors (right), and a precise 
determination of the horizontal measurement is maade by a small computer 
within the instrument. (Photograph by Robin T. Holcomb.)]

Changes in the shape of the volcano during inflation and deflation are 
determined by ground-deformation measurements. Tilt changes can be 
measured continuously and extremely precisely by use of instruments called 
tiltmeters, which can detect a change in angle of less than 1 microradian 
(about 0.00006 degree). A 1-microradian increase in tilt would be 
equivalent to steepening the slope of a 1-mile-long board by placing a 
nickel under one end. 

Tilt changes and associated relative vertical displacements also can be 
detected by periodic remeasurement of arrays of benchmarks by leveling, a 
high-precision field surveying method. Changes in horizontal distances 
between benchmarks can be monitored in the field by using portable 
electronic distance measurement (EDM) instruments that utilize laser or 
infra-red beams. Collectively, these commonly used ground-deformation 
monitoring techniques have a measurement precision of a few parts per 
million or less. The notion of one part per million can be visualized in 
terms of a very dry martini -- 1 drop of vermouth in 16 gallons of gin! 
 
[image caption: HVO scientists using an optical-level instrument to 
determine ground tilt, calculated from readings to three or more stadia 
rods (one seen at right). Use of umbrella improves readings by eliminating 
disruptive air-temperature fluctuations caused by passage of clouds. 
(Photograph by J.D. Griggs).]

Page 19

The mainstay of volcano monitoring is the continuous recording of seismic 
activity. Virtually all Hawaiian eruptions are preceded and accompanied by 
an increase in the number of shallow earthquakes. As magma moves into the 
reservoir during inflation, it must make room for itself by rupturing or 
crowding aside the solidified lava that surrounds the reservoir. Such 
underground ruptures produce seismic waves that travel through the volcano 
and are recorded by a network of seis- mometers placed on the volcano's 
surface. Ground motions sensed by the seismometer are converted into 
electronic signals, which are transmitted by radio and are recorded on 
seismographs located at the volcano observatory. The seismic data are 
analyzed to determine the time, location, depth, and magnitude of the 
earthquakes. Mapping the earthquake activity allows HVO scientists to 
track the subsurface movement of magma.

All Hawaiian eruptions are accompanied by harmonic tremor (also called 
volcanic tremor). Quite distinct from the discrete seismic shocks 
associated with rupture-caused earthquakes, harmonic tremor is a 
continuous vibration of the ground caused by magma movement. Harmonic 
tremor generally is detectable and recorded only by seismic 
instrumentation; however, if especially vigorous, tremor can be felt by 
people as far as 5 miles from the eruption site.

[image caption: Above left: A smoke-drum seismograph. A sharp-needle pen 
"writes" the seismic signature by scratching recording paper coated with 
carbon black (soot). (Photograph by Robert W. Decker.) For more precise 
monitoring, however, HVO records and analyzes seismic activity by use of
photographic-film and computerized magnetic-tape recording systems. Above 
right: Examples of common seismic signatures typically recorded before and 
during eruptions]

Page 20

Anatomy of an Eruption: The Inflation-Deflation Cycle

Kilauea's behavior during and between eruptions is remarkably regular. 
Monitoring instruments placed at the volcano's summit can used to trace 
the cycles of gradual inflation, in which the reservoir fills with magma, 
and abrupt deflation when the reservoir partially empties to deliver magma 
to an eruption. These recurring inflation- deflation cycles are precisely 
recorded by tiltmeters and seismometers, as well displayed during the 1983-
to-present Pu'u 'O'o eruption.

During inflation the rocks surrounding the reservoir become stressed, and 
this stress is partly relieved by increasing numbers of earthquakes, too 
small to be felt, but easily recorded by seismometers at Kilauea summit. 
These earthquakes (called short- period or tectonic) are recorded as high- 
frequency features on a seismograph. During deflation the stress is 
completely relieved. The short-period earthquakes stop, but their place is 
taken by low-frequency earthquakes (called long-period or volcanic), which 
reflect adjustments related to the exit of magma from the summit reservoir 
to feed the eruption. The long-period earthquakes are related to harmonic 
tremor, the continuous seismic record of underground magma movement. 

Kilauea's distinctive inflation-deflation pattern is seen for nearly every 
eruption, regardless of the amount of tilt change observed. For example, 
the pattern is dramatically shown for the Kilauea Iki eruption in 1959, 
which involved the largest tilt change observed to date (nearly 300 
microradians); the same pattern is also well shown for activity involving 
tilt changes of only 20 microradians or less, such as the continuing 
eruption at Pu'u 'O'o.


Forecasting Eruptions

A prime objective of volcano monitoring is to detect the early signs of 
possible eruptive activity and to make reliable eruption forecasts. 
Although considerable advances have been made in volcano monitoring in 
Hawaii, accurate long-term forecasts (one year or longer) still elude 
scientists. However, the capability for short-term forecasts (hours to 
months), especially of Kilauea's activity, is much better.

Accurate short-term forecasts of Hawaiian eruptions are based primarily on 
analyses of inflation-deflation patterns, made possible through decades of 
study of ground deformation (tilt) and seismicity (earthquakes and 
harmonic tremor). When the level of inflation and the short-period 
earthquake counts are high, the volcano is ready to erupt. Sometimes there 
is a delay of days or even weeks before eruption occurs, but scientists 
can be ready to study the activity when it occurs. Eruption is signaled by 
the beginning of sharp deflation accompanied by either harmonic tremor or 
earthquakes close to the site of eruptive outbreak. These signals are 
usually seen an hour to several hours before lava breaks the surface and 
allow scientists enough time to travel to the likely site of activity. 

Page 21

[graph of] Summit Tilt of Kilauea 1956-1986

[graph of] Pu'u 'O'o Eruptions, January-June 1986

[image caption: Above: The common pattern of gradual inflation, followed 
by abrupt deflation, is well demonstrated by major eruptions and 
intrusions. Below: Detailed look at a 6-month segment of the tilt record 
reveals similar inflation-deflation patterns for the high-lava fountaining 
episodes of Pu'u 'O'o eruption, even though the tilt changes and time 
intervals involved are much smaller (compare scales of the two drawings). 
Also well shown are the variation patterns of the two types of earthquakes 
that commonly precede and accompany Kilauea eruptions.]

Page 22

[map of] Volcano-monitoring networks on Hawaii

[image caption: The principal volcano- monitoring networks operated by the 
Hawaiian Volcano Observatory. For more information about these networks, 
see article by Heliker and others]

Page 23

The combination of seismic and ground- deformation monitoring has proved 
to be the most useful and liable technique in the short-term forecasting 
of eruptions at Kilauea. Some experimental techniques being developed or 
tested show promise and should increase forecasting capabilities in the 
future. These new methods include monitoring the changes in: the 
composition and amount of volcanic gases discharged (such as sulfur 
dioxide, carbon dioxide, hydrogen, helium, and radon); the magnetic and 
gravitational fields of the volcano; and the various geoelectrical 
properties of the volcano.

So far, the data from these experimental techniques have not given 
definitive precursors to possible eruptions. How- ever, they have 
identified underground movement of magma from one place to another, 
sometimes unaccompanied by measurable ground deformation or earthquakes. 
Experience on well-studied active volcanoes in Hawaii and elsewhere has 
shown that the best monitoring is achieved by using a combination of 
approaches rather than relying on any single method. 

At present, scientists generally can identify the increased potential for 
eruption of Kilauea or Mauna Loa and the likely location of the outbreak, 
but they cannot make specific forecasts of the exact timing or size of the 
expected eruption. However, for a number of Kilauea eruptions in recent 
decades, the HVO staff has been able to provide advice to officials of 
Hawaii Volcanoes National Park, hours to days in advance, to evacuate 
certain areas of the park and to station observers at or near the eruption 
site.

[image caption: Scientist using a correlation spectrometer (COSPEC) to 
measure the emission of sulfur dioxide gas from the Pu'u 'O'o vent. This 
instrument was originally developed to measure the discharge of sulfur 
dioxide from industrial smokestacks in monitoring atmospheric pollution. 
(Photograph by J.D. Griggs.)]

Page 24

Kilauea's Volcanic "Plumbing System"
 
From years of monitoring and research at HVO, Kilauea's volcanic "plumbing 
system" is now relatively well understood. This system links the processes 
involved in the formation, transport, storage, and, ultimately, eruption 
of magma to build and feed Hawaii's active volcanoes.

Kilauea's plumbing system is believed to extend deep beneath the Earth's 
surface, where basaltic magma is generated by partial melting of material 
beneath the Pacific Plate as it passes over the Hawaiian hot spot. This 
belief is based on the persistent recurrence of earthquakes 30 or more 
miles beneath Hawaii. Earthquakes occurring in the depth interval 20-30 
miles are probably related to the accumulation and upward movement of 
magma. Seismic data for levels shallower than 20 miles can be interpreted 
to define diffuse zones of continuous magma rise, one leading to Kilauea 
and another to Mauna Loa. 

Before Kilauea eruptions, most of the magma entering the volcano is stored 
temporarily within a shallow reservoir. Earthquake data and ground-
deformation patterns suggest that this reservoir is located 1 to 4 miles 
beneath the summit and consists of pockets of magma concentrated within a 
crudely spherical volume about 3 miles across. Earthquakes do not occur 
within the reservoir, because liquid magma does not rupture to generate 
and transmit certain seismic waves.

Kilauea eruptions occur either at its summit or within two well-defined 
swaths (called rift zones) that radiate from the summit. During summit 
eruptions, the magma reservoir deflates only slightly, if at all. This 
relation implies that the rate at which magma is erupted nearly equals 
that at which the reservoir is refilled by new magma from depth. During an 
eruption in a rift zone, called a rift or flank eruption, however, the 
summit region undergoes a significant and abrupt deflation as magma moves 
quickly from the summit reservoir into the rift zone. Similar summit 
deflation occurs during a rift intrusion, during which magma injected into 
the rift zone remains stored there rather than breaking the ground surface 
in an eruption. When the rift eruption or intrusion ends, the summit 
region reinflates as the shallow reservoir is refilled by magma from 
depth. Small pockets of summit-fed magma may be stored for a while within 
a rift zone and form transient secondary reservoirs. 

The volcanic plumbing system for Mauna Loa is less well known. Analysis of 
data from the well monitored 1975 and 1984 eruptions, however, suggests 
that the essential features of Kilauea's plumbing system are shared by 
Mauna Loa, despite the difference in size between the two volcanoes. Mauna 
Loa's magma reservoir also may be larger than Kilauea's, which would be 
consistent with the observations that Mauna Loa eruptions tend to be 
characterized by higher lava-output rates, longer eruptive fissures, and 
larger lava flows. 
 
Page 25

[image caption: Cut-away view looking deep beneath Kilauea Volcano, 
showing the shallow magma reservoir and the principal magma passageways. 
Areas in yellow are the most favorable zones for magma movement (arrows 
show direction) and storage. Though greatly generalized, this depiction of 
Kilauea's "plumbing system" is compatible with all known scientific 
information. (Figure by Michael P. Ryan, simplified from his technical 
illustrations in USGS Professional Paper 1350, Volume 2, Chapter 52.)]

Page 26

Eruptive Style: Powerful but Unsually Benign

By definition, the adjective eruptive describes any object or phenomenon 
associated with processes of "bursting forth," "breaking out," or "issuing 
forth suddenly and violently." Strictly speaking, no eruption is truly 
nonexplosive, but most Hawaiian eruptions closely approach being such. 
Indeed, the term "Hawaiian" is used by volcanologists worldwide to 
characterize similar eruptive style at other volcanoes.


Typical Activity: "Nonexplosive" or Weakly Explosive

With infrequent exceptions, eruptions of Hawaiian volcanoes are weakly 
explosive or nonexplosive and relatively benign. Hawaiian eruptions are 
typically gentle because their lava is highly fluid and thus tends to flow 
freely both beneath the surface and upon eruption. In contrast, lava of 
volcanoes located along plate margins, such as Mount St. Helens, generally 
is more viscous ("stickier" and "stiffer") and tends to fragment, often 
very explosively, during eruption. Highly fluid lava favors the nonviolent 
release of the expanding volcanic gases that drive eruptions. In contrast, 
viscous magma suppresses easy gas escape, which results in pressure build-
up underground and ultimately in explosive gas release and magma 
fragmentation.

Lava viscosity ("stiffness" or "resistance to flow") is largely determined 
by the chemical composition and temperature of the magma, the amount of 
crystals in the magma, and the gas content. The high fluidity (low 
viscosity) of Hawaiian lavas derives mainly from its basaltic composition, 
characterized by more iron (Fe), magnesium (Mg), calcium (Ca), and 
titanium (Ti), and less silicon (Si), aluminum (Al), sodium (Na), and 
potassium (K), compared to such viscous lavas as the dacite erupted 
explosively at Mount St. Helens in 1980. In the graph showing this 
compositional difference between Hawaiian basalt and Mount St. Helens 
dacite, the chemical elements are given as oxides [(for example, calcium 
as calcium oxide (CaO)]. Basalt is dark volcanic rock made up of small 
crystals and glass, whereas dacite, while also glassy or fine-grained, 
generally is much lighter in color.

Hawaiian eruptions typically start with lava fountains spouting from a 
series of nearly continuous fissures, "curtain(s) of fire." As most 
eruptions progress, lava-fountain activity becomes localized at a single 
vent (an opening from which lava issues), generally within hours of the 
initial outbreak. Depending on the shape of the vent and other eruptive 
conditions, lava fountains can vary widely in form, size, and duration. 

[image caption: Left: Mount St. Helens, a typical steep-sided composite 
volcano, shortly before its decapitation by the May eruption in 1980. 
(Photograph courtesy of D.R. Pevear, Western Washington University, 
Bellingham.) Right: Mauna Loa, an excellent example of a shield volcano, 
viewed from the Hawaiian Volcano Observatory. (Photograph by Robert I. 
Tilling.).]

Page 27

[image caption: Above: Graph illustrating the difference in average 
chemical compositions between lava erupted by Hawaiian volcanoes and by 
Mount St. Helens in 1980. The number given for each chemical element gives 
the amount (in weight percent) of that element (expressed as oxide) 
contained in the lava. Left: Note the contrast in color and texture 
between Hawaiian basalt (dark) and Mount St. Helens dacite (light). 
(Photograph by J.D. Griggs).]

Page 28

[image caption: Lava fountains can vary widely in size and form. Center: 1,
900-foot high fountain during Kilauea Iki eruption in 1959, the highest 
ever observed anywhere in the world. (Photograph courtesy of the National 
Park Service.) Right above: A discontinuous row of lava fountains 
("curtains of fire") 50-100 feet high during the 1971 Kilauea summit 
eruption as viewed from the air. (Photograph courtesy of the National Park 
Service.) Right below: "Curtain of fire" viewed from the ground during the 
1984 Mauna Loa eruption. (Photograph by Richard B. Moore.)]

Page 29

[image caption: Left: Night view (time-exposure) of a "spray" lava 
fountain, 50-70 feet high, during the 1972-74 Mauna Ulu eruption of 
Kilauea. (Photograph by Robin T. Holcomb.) Top: A 40-foot arching "hose" 
fountain spurts from Pu'u 'O'o vent in 1983. (Photograph by J.D. Griggs.) 
Bottom: A "dome" fountain, about 45 feet high, plays continuously for 
hours during the 1969-71 Mauna Ulu eruption. (Photograph by Jeffrey B. 
Judd.)]

Page 30

During the 1959 Kilauea Iki eruption, lava fountains shot 1,900 feet, the 
record height for historic Hawaiian eruptions and likely the highest lava 
fountain yet observed on Earth. More recently, some of the vigorous 
eruptive episodes of the 1983-to-present Pu'u 'O'o activity have produced 
lava fountains about 1,500 feet high. Though impressive, even these 
spectacularly high lava fountains are products of relatively weak 
explosive activity. By comparison, the May 1980 explosive eruption of 
Mount St. Helens sent ash more than 12 miles into the atmosphere. When the 
rate of gas release is too low to cause fountaining, lava merely wells up, 
flows quietly, or oozes from the vent.

Lava falling from fountains and issuing quietly from vents often forms 
incandescent lava streams or lava flows, leading to the colorful term 
"rivers of fire," often used in popular accounts of Hawaiian eruptions. 
During some Mauna Loa eruptions, several lava flows rushed down the steep 
slopes at 35 miles per hour! During long-lived eruptions, lava flows tend 
to become "channeled" into a few main streams. Overflows of lava from 
these streams solidify quickly and plaster on to the channel walls, 
building natural levees or ramparts that allow the level of the lava to be 
raised. Lava streams that flow steadily in a confined channel for many 
hours to days may develop a solid crust or roof and thus change gradually 
into streams within lava tubes. Because the walls and roofs of such tubes 
are good thermal insulators, lava flowing through them can remain hot and 
fluid much longer than surface flows. Tube-fed lava can be transported for 
great distances from the eruption sites. For example, during the 1969-74 
Mauna Ulu eruptions at Kilauea, lava flows traveled underground through a 
lava-tube system more than 7 miles long to enter the ocean on five 
occasions. 

[image caption: Red-hot blobs of liquid lava ejected during one of the 
high-fountaining episodes at Pu'u 'O'o are transformed to solid black 
fragments upon rapid cooling in flight. Helicopter (upper left) gives 
scale. (Photograph by J.D. Griggs.)]

Page 31

[image caption: Center: Aerial view of braided lava flow of the 1984 Mauna 
Loa eruption. With imagination, some people see in this flow pattern the 
figure of Pele, Goddess of Volcanoes, with her arms raised. (Photograph by 
Maurice Krafft, Centre de Volcanologie, Cernay, France.) Above right: 
Inside the Thurston Lava Tube, Hawaii Volcanoes National Park. (Photograph 
by Taeko Jane Takahashi.) Below right: How Thurston Lava Tube might have 
looked when it was "active" a few hundred years ago can be appreciated 
from this view through the collapsed roof ("skylight") of a lava tube 
active during the 1969-71 Mauna Ulu eruption. (Photograph by Jeffrey B. 
Judd.)]

Page 32

Lava streams that plunge over cliffs or the steep walls of craters form 
impressive lava cascades or lava falls. Where cascades spill into 
preexisting craters, lava lakes may be formed. Such lakes are considered 
inactive and generally form a solid crust within hours or a few days. The 
still molten lava beneath this crust then takes weeks to years, depending 
on lake size, to cool and solidify completely. Lava lakes formed at the 
site of, and sustained by, active eruptive vents are considered active. 
The crust formed on these lakes is not permanent and breaks up in response 
to circulation and sloshing of the underlying molten lava. Repeated 
overflows from active lava lakes raise their level by rampart construction 
similar to overflowing lava streams. By this process of levee growth, 
lakes may become perched many feet above their surroundings.  

[image caption: Right: Lava cascades plunge 160 feet into Lua Hou Crater, 
upper part of Mauna Loa's southwest rift zone, during July 1975 eruption. 
(Photograph by Robin T. Holcomb.) Below: A clockwise-circulating lava lake 
(nearly 500 feet across) in Pauahi's west pit formed during the same 
eruption. Bright small spots seen on the lake surface are caused by trees 
bursting into flame. (Photograph by Robert I. Tilling.)]

Page 33

The century-long lava-lake activity at Halemaumau ceased after the 
explosive 1924 eruption; however, a lava lake was active there for about 8 
months during the 1967-68 eruption. Not until the 1969-1974 Mauna Ulu 
eruptions, on Kilauea's upper east rift zone, however, did scientists have 
an opportunity to observe the development and behavior of a  
long-lived active lava lake outside the summit region of a Hawaiian 
volcano. The lava-lake behavior at Mauna Ulu, including movement and 
collision of thin plates of surface crust floating on circulating molten 
lava, provided a small-scale version of the Earth's global plate tectonics.

[image caption: Surface movements of the active lava lake within Mauna Ulu 
crater in 1971 provide an instructive, but very small scale, analogy to 
movements of the Earth's tectonic plates. Left: View looking east and down 
(about 200 feet) at the lava-lake surface. Center: Closer view of moving 
slabs of solidified crust, ranging in size from a few feet to several tens 
of feet across but only a few inches thick, rafted by circulating lava 
beneath. Right: Even closer views of lake surface to show small-scale 
analogs to the three common types of boundaries between tectonic plates: 
Convergent boundary between two slabs of crust (upper); Divergent or 
spreading boundaries between three slabs (middle); and Transform fault 
(lower) offsetting the spreading boundary between two slabs. (Photographs 
by Wendell A. Duffield.)]

Page 34

Infrequent Explosive Activity
  
Explosive eruptions that deposit large volumes of pyroclastic debris over 
large areas -- like the May 1980 eruption of Mount St. Helens -- are rare 
at Hawaiian volcanoes. The term "pyroclastic" -- derived from Greek pyro 
(fire) and klastos (broken) -- is a general term to describe all types of 
fragmented new magma or old solid rock ejected during explosive eruptions. 
Less than 1 percent of Hawaiian eruptions have been violently explosive, 
based on the scarcity of pyroclastic deposits. In contrast, some volcanic 
chains formed along the convergent boundaries of the Earth's tectonic 
plates contain 90 percent or more pyroclastic material. 

In 1790, a series of major explosive eruptions, which probably lasted a 
few days to a few weeks, deposited a blanket of pyroclastic debris up to 
30 feet thick in and around Kilauea summit.

At the time of these eruptions, a band of about 250 Hawaiian warriors, led 
by Keoua, chief of the Puna district in eastern Hawaii, was marching 
across the summit region of Kilauea to battle the army of a rival chief, 
Kamehameha. Some of Keoua's warriors were caught in a hot, high-velocity 
explosion cloud, composed mainly of volcanic steam and gases but little 
ash. The hot gases seared the warriors' lungs, killing about 80 of them by 
suffocation. Footprints preserved in the muddy ash deposits of the 1790 
eruption are thought to be those of the surviving warriors; these still 
can be seen by hiking the Mauna Iki (Footprints) Trail in Hawaii Volcanoes 
National Park. Had the Hawaiian Volcano Observatory been at its present 
location on the summit of Kilauea in 1790, it almost certainly would have 
been destroyed.

A much less energetic explosive eruption took place at Halemaumau Crater 
in May 1924. Three months before the eruption, the long-lived lava lake in 
Halemaumau played actively about 150 feet below the crater rim. Beginning 
in February, the lake surface began to drop rapidly, and soon the lake 
drained entirely to expose the crater floor. Throughout March and April, 
the crater floor further subsided, apparently in response to magma moving 
from the summit reservoir into the east rift zone. By May 6, Halemaumau's 
floor was more than 600 feet below the rim. 

[image caption: This footprint and others preserved in the muddy ash 
deposits of Kilauea's explosive eruption in 1790 are believed to be those 
of Hawaiians who survived the hot explosion cloud. (Photograph by James F. 
Martin, National Park Service.)]

Page 35

[image caption: Tourists posing in May 1924 (at a safe distance!) at 
Kilauea Volcano as a large explosion cloud rises thousands of feet into 
the air. (Photograph courtesy of the Bishop Museum.)]

A series of steam explosions began on May 10 at Halemaumau and continued 
vigorously for two and a half weeks. Each explosion lasted from a few 
minutes to 7 hours; the most powerful ones sent ash plumes more than a 
mile high and hurled large blocks, some weighing several tons, more than a 
half mile from Halemaumau. Many of these blocks were red hot. A 
photographer, who ventured too close to the crater, was struck by a 
falling block and died the next day from his injuries. When the explosions 
ended, Halemaumau was about twice as wide, and eight times as deep, as 
before the eruption.

The 1790 and 1924 eruptions were explosive because they involved the 
violent mixing of ground water and magma or hot rocks. During both 
eruptions, as the the magma column subsided in the vent, ground water came 
into sudden contact with hot material and flashed explosively to steam. 
The 1924 eruption ejected only chunks of solid, hot older rocks; none was 
newly formed from magma. The 1790 eruption expelled fragments of solid, 
older rocks and new magmatic material, suggesting that ground water mixed 
with both. Though impressive, the 1924 explosions produced only about one-
tenth of 1 Percent of the volume of the 1790 explosions.  

Page 36

The pyroclastic deposits exposed at Kilauea indicate that about two dozen 
major explosive eruptions have occurred during the past 70,000 years. 
Mauna Loa apparently has had less frequent explosive eruptions during the 
same time interval. Judging by their distribution and thickness, Kilauea's 
prehistoric pyroclastic deposits had to be produced by explosive eruptions 
at least as powerful as the 1790 eruption and, in some cases, several 
times stronger. 

A special type of explosive activity, called a littoral explosion, 
occasionally results when lava flows enter the ocean. Seawater comes into 
contact with the hot inner part of the lava flow and flashes into steam, 
triggering an explosive spray of fragments derived from both the 
solidified outer part of the lava flow as well as its still-molten core. 

Because of their seashore locations, most small deposits from littoral 
explosions are quickly removed by erosive action of the ocean surf. Larger 
deposits, however, are more permanent and form littoral cones, such as the 
100-foot-high Pu'u o Mahana, near the south tip of the Big Island, formed 
during a prehistoric Mauna Loa eruption.

Pu'u o Mahana is the site of Hawaii's famous "green sand beach," composed 
of the shiny green mineral olivine (a magnesium-iron-silicate) eroded from 
the littoral cone and concentrated by wave action. The conspicuous 
occurrence of olivine, sometimes also called "Hawaiian diamond," in the 
pyroclastic deposits that form the prominent cone that is Honolulu's 
landmark reportedly prompted early visitors to name it "Diamond Head." 
Peridot, a gem-quality variety of olivine, is the birthstone for the month 
of August. 

[image caption: Center: Molten lava being shredded by littoral explosions 
upon entry into the ocean during the 1969-71 Mauna Ulu eruption. 
(Photograph by Donald W. Peterson.) Right above: Pu'u o Mahana, a 
prehistoric littoral cone of Mauna Loa, is the site of the Big Island's 
green-sand beach. (Photograph by J.D. Griggs.) Right below: Close-up of 
the green sand, which obtains its color from wave- concentrated grains of 
the green mineral olivine. (Photograph by Robert I. Tilling.)]

Page 37

Hawaiian Volcanic Products, Landforms, and Structures

The volcanic mountains of Hawaii have been built by the accumulation of 
basalt flows erupted over hundreds of thousands of years, as the Pacific 
Plate moved northwestward over the hot spot. In contrast, the volcanic 
mountains in the zones where tectonic plates converge, such as Mount St. 
Helens and the other volcanoes of the Cascade Range, have been built 
primarily by pyroclastic debris. Even though they both form linear 
mountain ranges, the Hawaiian volcanoes differ greatly from the Cascade 
volcanoes in mode of origin and types of volcanic rocks.

Molten lava can solidify in a variety of ways, depending on eruption 
conditions and gas content of the erupting magma. Volcanic products of 
Hawaiian eruptions are mostly dark in color but vary widely in form and 
texture.


Lava Flows

Lava flows form more than 99 percent of the above-sea parts of Hawaiian 
volcanoes. Pahoehoe (pronounced "pah-hoy-hoy") and aa (pronounced "ah-ah") 
are the two main types of Hawaiian lava flows, and these two Hawaiian 
names, introduced into the scientific literature in the late 19th century, 
are now used by volcanologists worldwide to describe similar lava-flow 
types. Pahoehoe is lava that in solidified form is characterized by a 
smooth, billowy, or ropy surface, while aa is lava that has a rough, 
jagged, spiny, and generally clinkery surface. In thick aa flows, the 
rubbly surface of loose clinkers and blocks hides a massive, relatively 
dense interior.  

[image caption: Center: An active clinkery aa lava flow advances over the 
smooth surface of earlier erupted pahoehoe lava during the 1972-74 Mauna 
Ulu eruption. (Photograph by Robert I. Tilling.) Right: Closer views of 
the surface of an aa flow (above) and a pahoehoe flow (below). 
(Photographs by J.D. Griggs and Taeko Jane Takahashi, respectively.)]

Page 38

The contrast between the surfaces of pahoehoe and aa flows is immediately 
obvious to anyone hiking Hawaiian lava fields. Walking on dense pahoehoe 
can almost be as easy as strolling on a paved sidewalk. But walking across 
aa is like scrambling over a building-demolition site or battle zone, 
strewn with loose, unstable debris of all shapes and sizes. The jagged 
rubble of aa flows quickly destroys field boots and, should the hiker 
stumble or fall (not at all uncommon), it can tear clothing and flesh.

Many Hawaiian lava flows solidify as pahoehoe throughout their extent, and 
a few flows solidify completely as aa. Most flows, however, consist of 
both pahoehoe and aa in widely varying proportions. In a given flow, 
pahoehoe upstream commonly changes to aa downstream, but aa lava flows do 
not change into pahoehoe flows. The explanation for this oneway change 
lies in the delicate balance between the initial gas content of the lava, 
the changes in lava viscosity, and the rate of deformation ("shear 
strain") of the lava during flow and cooling. Once this critical balance 
is upset, pahoehoe can change to aa.

Hawaiian lava is fluid enough to travel great distances, especially if it 
is transported through lava tubes. Some historic flows are longer than 30 
miles; in general, pahoehoe flows tend to be longer than aa. Lava tubes 
may be preserved when the eruption ends and the lava drains away to leave 
open tunnels. They may be as much as several tens of feet in diameter, and 
some have been followed by spelunkers (cave explorers) for nearly 10 
miles. Ancient Hawaiians used lava tubes as places of shelter and as 
burial caves. Visitors to Hawaii Volcanoes National Park can walk through 
Thurston Lava Tube, which formed in a pahoehoe flow a few hundred years 
ago.

Fluid lava erupted or flowing under water may form a special structure 
called pillow lava. Such structures form when molten lava breaks through 
the thin walls of underwater tubes, squeezes out like toothpaste, and 
quickly solidifies as irregular, tongue-like protrusions. This process is 
repeated countless times, and the resulting protrusions stack one upon 
another as the lava flow advances underwater. The term pillow comes from 
the observation that these stacked protrusions are sack- or pillow-shaped 
in cross section. Typically ranging from less than a foot to several feel 
in diameter, each pillow has a glassy outer skin formed by the rapid 
cooling of the lava by water. Much pillow lava is erupted under relatively 
high pressure created by the weight of the overlying water; there is 
little or no explosive interaction between hot lava and cold water. The 
bulk of the submarine part of a Hawaiian volcano is composed of pillow 
lavas.

[image caption: Below: SCUBA-diving scientist's view of incandescent lava 
breaking through the solidified shell of a pillow-lava lobe to form 
another tongue as underwater flow advances during the 1969-71 Mauna Ulu
eruption. (Photograph by Richard Grigg, University of Hawaii.) Right: 
Pillow lava on the submerged western slope of Mauna Loa at a water depth 
of about 2,500 feet. The research submarine's mechanical arm (right) can 
be manipulated by scientists on board to collect samples. (Photograph by 
Daniel Fornari, Lamont-Doherty Geological Observatory of Columbia 
University.)]

Page 39

Abundant studies in recent decades, by remotely controlled deep-sea 
cameras as well as by small, manned research submarines, demonstrated the 
widespread occurrence of pillow lavas in areas of submarine volcanism. It 
was not until 1970, however, that the underwater formation of pillow lava 
was directly observed. Twice during the 1969-74 Mauna Ulu eruptions of 
Kilauea, teams of SCUBA-diving scientists watched and filmed pillow lavas 
being formed as lava flows entered the sea. Well-formed pillows also have 
been studied on the submarine parts of Kilauea and Mauna Loa, as well as 
the submerged parts of the 1800-1801 lava flows of Hualalai Volcano off 
the west coast of Hawaii.

Another common lava product is the ponded flow or lava lake, the formation 
of which has been described earlier in connection with eruptive style of 
Hawaiian volcanoes. The surface of lava that is ponded is smooth, broken 
only by polygonal cooling cracks, formed in much the same way as shrinkage 
cracks in mud that has been dried by the sun. Lava lakes were formed in 
Alae (1963 and 1968), Makaopuhi (1965), and Kilauea Iki (1959) Craters. 
The deep lava lake (350 feet) formed during the November-December 1959 
eruption at Kilauea Iki is the only one of these still easily visible and 
accessible. 

The lava lakes have been investigated in detail because they furnish 
natural crucibles for study of the cooling, crystallization, and chemical 
change of basaltic lava. These studies have included drilling holes 
through the solid crust of the lake to measure temperature and other 
properties and to sample the still-molten lava in the interior. lo 
physical terms, the formation of the lava lake's solid crust by cooling 
can be compared to the formation of a sheet of ice on top of a body of 
water during a winter freeze. By 1987, all of the still-molten 1959 lava 
in the interior of the lake at Kilauea Iki will have solidified, although 
the internal temperature of the lake will remain hundreds of degrees 
hotter than the surface temperature for many more years. 
 
[image caption: Above: Specimens from the 1965 lava lake in Makaopuhi 
Crater (about 2 miles east of Mauna Ulu), sampled by drilling, as seen 
under the microscope (field of view about 0.05 inch). The amount and kinds 
of crystals increase with decreasing temperatures as the lava lake cools.
(Photomicrographs by Thomas L. Wright.) Top right: Looking about 400 feet 
down from the rim of Kilauea Iki Crater to the surface of the lava lake 
formed in the 1959 eruption and a site of drilling studies (oval). Bottom 
right: Close-up of drilling operations. HVO scientists wear asbestos 
gloves in handling hot drilling steel. (Photographs by Robin T. Holcomb.)]

Page 40

Drilling of lava lakes can be risky. When the Mauna Ulu eruption began on 
May 24, 1969, a lava flow poured into Alae Crater and quickly buried a 
drill rig and related equipment before they be could be lifted out by 
helicopter! A more common risk is posed by the occasional minor steam 
explosions in the drillholes caused by contact of cooling water with the 
molten lava.


Fragmental Volcanic Products

Fragmental volcanic debris is formed during mildly explosive activity, 
such as lava fountaining, and, less commonly, during the infrequent 
violently explosive eruptions, such as during 1790 at Kilauea. Tephra is 
the general term now used by volcanologists for airborne volcanic ejecta 
of any size. Historically, however, various terms have been used to 
describe ejecta of different sizes. Fragmental volcanic products between 
0.1 to about 2.5 inches in diameter are called lapilli; material finer 
than 0.1 inch is called ash. Fragments larger than about 2.5 inches are 
called blocks if they were ejected in a solid state and volcanic bombs if 
ejected in semi-solid, or plastic, condition. In a major explosive 
eruption, most of the pyroclastic debris would consist of lapilli and ash. 
Volcanic bombs undergo widely varying degrees of aerodynamic shaping, 
depending on their fluidity, during the flight through the atmosphere. 
Based on their shapes after they hit the ground, bombs are variously 
described, in graphic terms, as "spindle or fusiform," "ribbon," "bread-
crust," or "cow-dung." 

[image caption: Shiny strands of volcanic glass, called Pele's hair 
(above) are commonly found downwind from active eruptive vents. Volcanic 
spatter commonly becomes tightly welded to form mounds around active vents 
(below). (Photographs by Donald W. Peterson and Richard P. Moore, 
respectively.)]

Page 41

Another category of ejecta far more common than volcanic bombs is scoria 
or cinder, which refers to lapilli- or bomb-size irregular fragments of 
frothy lava. If the cinder contains abundant vesicles (gas-bubble 
cavities), it is called pumice, which can be light enough to float on 
water if the vesicles are closed to rapid filling by water. In Hawaii, 
these fragments share a common mode of origin: all result from sudden 
chilling of frothy lava from which gases were escaping during fountaining. 
During the exceptionally high fountaining episodes of some eruptions, such 
as at Kilauea Iki in 1959 or at Pu'u 'O'o (all episodes, 1983 to present), 
an extremely vesicular, feathery light pumice, called reticulite or thread-
lace scoria, can form and be carried many miles downwind from the high 
lava fountains. Even though reticulite is the least dense kind of tephra, 
it does not float on water, because its vesicles are open and 
interconnected. Consequently, when it falls on water, it becomes easily 
waterlogged and sinks. 

If the scoria or pumice clots are sufficiently soft to flatten or splash 
as they strike the ground, they are called spatter. The still-molten 
character of spatter fragments can cause them to stick together to form 
welded spatter or agglutinate. Drops of lava ejected in very fluid 
condition and solidified in flight can form air-streamlined spherical, 
dumbbell, and irregular shapes. Drop-shaped lapilli are called Pele's 
tears, after the Hawaiian Goddess of Volcanoes. In streaming through the 
air, Pele's tears usually have trailing behind them a thin thread of 
liquid lava, which is quickly chilled to form a filament of golden brown 
glass, called Pele's hair. Pele's hair can form thick mats downwind from 
high lava fountains near a vent; it also can be blown many miles from the 
vent.

[image caption: Some common Hawaiian fragmental volcanic products (top to 
bottom): reticulite; Pele's tears; volcanic bombs; and accretionary 
lapilli, spherical accumulations of volcanic ash, generally formed during 
violently explosive eruptions. (Top two photographs by J.D. Griggs, bottom 
two photographs by John P. Lockwood.)]

Page 42

Volcanic Landforms and Structures

Hawaiian volcanoes exemplify the common type of volcano called a shield 
volcano, built by countless outpourings of fluid lava flows that advance 
great distances from a central summit vent or group of vents. The 
successive piling up of these flows results in a broad, gently sloping, 
convex-upward landform, whose profile resembles that of a Roman warrior's 
shield.

The Hawaiian shield volcanoes are the largest mountains on Earth. Mauna 
Kea Volcano rises 13,796 feet above sea level but extends about 19,700 
feet below sea level to meet the deep ocean floor. Its total height is 
nearly 33,500 feet, considerably higher than the height of the tallest 
mountain on land, Mount Everest (Chomolungma) in the Himalaya (29,028 feet 
above sea level). Mauna Loa stands not quite as high as Mauna Kea but is 
much larger in volume. The profile of the Mauna Loa shield appears smooth, 
whereas the shield profile of Mauna Kea has a more uneven appearance, 
reflecting the growth of numerous small cinder cones on its upper slopes 
after shield formation. In size, composite volcanoes are dwarfed by the 
Hawaiian shield volcanoes. 

[image caption: Aerial view of some of the prominent fissures within the 
southwest rift zone of Kilauea Volcano. The shiny dark lava was erupted 
from these fissures in September 1971. (Photograph by J.D. Griggs.)]

[image caption: Profile of Hawaiian shield volcanoes compared with the 
profile of Mount Rainier, one of the larger composite volcanoes of the 
Cascade Range, drawn at the same scale.]

Page 43

[image caption: Aerial view from the south of snow-covered Mokuaweoweo, 
the summit caldera of Mauna Loa Volcano, and several pit craters of its 
southwest rift zone, Mauna Kea Volcano, which last erupted about 3,000 
years ago, can be seen in the distance. (Photograph by Donald W. 
Peterson.)]

Hawaiian and other shield volcanoes characteristically have a broad 
summit, indented with a caldera, a term commonly used for a large 
depression of volcanic origin. Most calderas form by collapse because of 
removal of magma from the volcano's reservoir by eruption and/or 
intrusion. Kilauea's summit caldera is about 2.5 miles long and 2 miles 
wide. Mokuaweoweo, the summit caldera complex of Mauna Loa is more 
elongate, measuring about 3 by 1.5 miles. The terms crater or pit crater 
are applied to similar but smaller collapse features.

Rift zones radiate from the summit calderas of both Mauna Loa and Kilauea 
and extend down the volcanic flanks into the sea. They are elongate 
tapering ridges expressed by prominent open fissures, pit craters, cinder 
and spatter cones, and small volcanic shields. The orientation of rift 
zones is influenced by the gravitational stresses and buttressing effects 
of pre-existing neighboring volcanoes. Most Hawaiian eruptions take place 
either within summit calderas or along rift zones.

Page 44

[image caption: Growth profiles of Kilauea's newest volcanic cone, built 
during the Pu'u 'O'o eruption.]

[image caption: Aerial view of some scarps of the Hilina Fault System, 
expressed as sharp cliffs on the south flank of Kilauea Volcano. 
(Photograph by Donald A. Swanson.)]

Repeated forceful intrusions of magma into the rift zones of Kilauea have 
pushed that volcano's south flank southward toward the sea. This seaward 
movement is readily measurable at rates as high as a few inches per year. 
Eventually the accumulated sea-ward movement causes the south flank to
become unstable, ultimately resulting in a large earthquake. Such 
earthquakes occur periodically and are accompanied by substantial and 
sudden movements along faults cutting the south flank (the Hilina Fault
System). For example, in response to a magnitude-7.2 earthquake beneath 
the area on November 29, 1975, points on Kilauea's south flank dropped as 
much as 11 feet and shifted southward as much as 24 feet. The scarps 
(steep slopes) of the Hilina faults are well expressed as palis (Hawaiian 
for cliffs) on Kilauea's south flank.

Prolonged eruptions on Kilauea's east rift zone have given scientists 
unprecedented opportunities to observe the growth of Hawaiian volcanic 
landforms. The 1969-74 eruptions created two prominent volcanic shields: a 
symmetrical 397-foot-high mound at Mauna Ulu (Hawaiian for "growing 
mountain") and, abutting it, a more irregular shield, 328 feet high, over 
the site of buried Alae Crater. The highest volcanic landform of historic 
age in Hawaii is the cone being built by the 1983-to-present Pu'u 'O'o 
eruption. By September 1986, this cone had grown to a height of more than 
830 feet.

Page 45

Loihi: Hawaii's Newest Volcano

If the hot-spot theory is correct, the next volcano in the Hawaiian chain 
should form east or south of the Big Island. Abundant evidence indicates 
that such a new volcano exists at Loihi, a seamount (or submarine peak) 
located about 20 miles off the south coast of the Big Island. Loihi rises 
10,100 feet above the ocean floor to within 3,100 feet of the water 
surface. Recent detailed mapping shows Loihi to be similar in form to 
Kilauea and Mauna Loa. Its relatively flat summit apparently contains a 
caldera about 3 miles across; two distinct ridges radiating from the 
summit are probably rift zones. 

Photographs taken by deep-sea camera show that Loihi's summit area has 
fresh-appearing, coherent pillow-lava flows and talus blocks. Examination 
of samples dredged from Loihi indicates that the pillow-lava fragments 
have fresh glassy crusts, indicative of their recent formation. The exact 
ages of the sampled Loihi flows are not yet known, but certainly some 
cannot be more than a few hundred years old. In fact, the occurrence of 
earthquake swarms at Loihi during 1971- 1972, 1975, and 1984-85 suggests 
major submarine eruptions or magma intrusions into the upper part of 
Loihi. Thus, Loihi appears to be a historically active, but as yet 
submarine, volcano.

[image caption: Above: A 3-man research submarine, the DSV Sea Cliff, is 
transported on the stern of its mother ship, the Maxine D. Below: The Sea 
Cliff being launched for a dive. (Photographs by Daniel Fornari, Lamont-
Doherty Geological Observatory of Columbia University.)]

Page 46

Seismic data also indicate that the deepest earthquakes beneath Loihi 
merge with the deep earthquakes beneath neighboring Kilauea. This downward 
convergence implies that Loihi apparently is tapping the same deep magma 
supply that Kilauea and Mauna Loa tap. The triangular zone defined by the 
summits of these three active volcanoes perhaps can be taken to lie over 
the postulated Hawaiian hot spot. 

Studies of Loihi provide a unique opportunity to decipher the youthful 
submarine stage in the formation and evolution of Hawaiian volcanoes. When 
might the still-growing Loihi emerge above the surface of the Pacific to 
become Hawaii's newest volcano island? It will almost certainly take 
several tens of thousands of years, if the growth rate for Loihi is 
comparable to that of other Hawaiian volcanoes. It is also possible that 
Loihi will never emerge above sea level and that the next link in the 
island chain has not yet begun to form. 

[image caption: Above: Map showing the locations of earthquakes that 
occurred during 1971-72 and 1975 in the vicinity of Loihi. These two 
earthquake swarms, plus a similar occurrence in 1984-85, provide seismic 
evidence that Loihi is an active submarine volcano. Left: The flank of 
Loihi, showing broken pillow lava of a fresh flow, as seen from about 7 
feet above the volcano's surface at a water depth of about 4,200 feet. 
(Photograph by Alexander Malahoff, University of Hawaii.)]

Page 47

Volcanic Hazards and Benefits

In the short term--on a human time scale--some Hawaiian eruptions can be 
extremely destructive, causing major disruptions in the daily lives of the 
people affected by them. On a geologic time scale (thousands to millions 
of years), however, the eruptions have been beneficial.


Volcanic Hazards

More than 270,000 people have been killed directly or indirectly by 
volcanic activity worldwide during the past 500 years. Nearly all of the 
deaths have been caused by explosive eruptions of composite volcanoes 
along the boundaries of the Earth's tectonic plates. The worst recent 
volcanic disaster was in November 1985, when mudflows triggered by 
relatively small eruption of glacier-capped Nevado del Ruiz Volcano, 
Colombia, buried the town of Armero and killed more than 22,000 people. In 
contrast, fewer than a hundred people have been killed by eruptions in the 
recorded history of Hawaii and only one of them in this century.
 
[image caption: Left: House being consumed by advancing lava during the 
1960 Kapoho eruption of Kilauea. (Photographer unknown.) Below: View of 
Kapoho village during the 1960 eruption before it was entirely destroyed 
(photographer unknown) and a post-eruption scene showing the remnants of 
corrugated iron roofs to mark the site of the lava-buried village 
(photograph by Robert 1. Tilling).]

Page 48

[image caption: Night view of the lava flows of the 1984 Mauna Loa 
eruption with lights of downtown Hilo in foreground. (Photograph by David 
Little.)]

Although the typically gentle Hawaiian eruptions pose little danger to 
people, their lava flows can be highly destructive to populated and 
cultivated areas. For example, the village of Kapoho was entirely 
destroyed during the 1960 eruption in the lower east rift zone of Kilauea. 
More recently, flows from Kilauea's Pu'u 'O'o eruption have covered and 
destroyed dwellings and house lots in the Royal Gardens subdivision on the 
volcano's southeastern flank. The outskirts of Hilo, the largest city on 
the Big Island, with a population of about 40,000, are built in part on 
the pahoehoe lava flows of the 1881 Mauna Loa eruption. During the March-
April 1984 eruption of Mauna Loa, Hilo was threatened. Lava flows advanced 
nearly 16 miles in about 5 days, and a bright red glow in the sky over the 
area of the incandescent flows could be seen on clear nights. The citizens 
and officials of Hilo became increasingly concerned as the eruption 
continued. Fortunately the flows stopped about 4 miles short of the 
nearest buildings on the city's outskirts.

Because of the frequent eruptions of Kilauea and Mauna Loa, the Hawaiian 
Volcano Observatory conducts round-the-clock monitoring to detect early 
signs of impending activity and to advise local officials on a timely 
basis. A key component in reducing volcanic hazards is the preparation of 
volcanic-hazards zonation maps. These maps delineate the zones of relative 
severity of volcanic hazards based on an assessment of data on eruption 
frequency; nature of expected activity; and likely vent areas and lava-
flow paths. 

It is useful to distinguish between the terms hazards and risks. 
Evaluation of hazards is based on geologic information only and considers 
the likelihood of destructive volcanic phenomena and products in a given 
area; assessment of risks evaluates the likelihood of loss of life and 
property in the area being considered. Thus, volcanic "risk" increases as 
the zones defined as hazardous become cultivated, populated, or otherwise 
developed. Even areas with a very low severity of volcanic hazards may be 
classified as high risk if they are densely populated. Hazards-zonation 
maps provide government officials and the public with critical information 
that allows them to assess the risks of volcanic hazards and apply the 
results in long-term land-use planning, estimates of the socioeconomic and 
political impact of eruptions, and preparation of contingency plans in 
case of volcanic emergencies. 

A volcanic-hazards map has been prepared for the Big Island, in which the 
the areas of increasing relative severity of hazards from lava flows are 
designated "9" through "1." Related maps have been prepared for hazards 
from air-fall ash, ground failures, and subsidence. Similar volcanic 
hazards-assessment studies have been made for the islands of Maui and 
Oahu, although the expected frequency of future eruptions on those islands 
is much lower. Boundaries drawn between the hazard zones are necessarily 
gradational and reflect the judgment of experienced volcanologists. 
Hazards-assessment studies assume that probable future eruptive behavior 
is most likely to be similar to a given volcano's past behavior. As a 
volcano's eruptive history becomes better documented by additional 
studies, the hazards-zonation maps for it need to be revised and updated 
to reflect the incorporation of new and better information.

Page 48

[image caption: Map of the Big Island showing the volcanic hazards from 
lava flows. Severity of the hazard increases from zone 9 to zone 1. Shaded 
areas show land covered by historic flows from three of Hawaii's five 
volcanoes (Hualalai, Mauna Loa, and Kilauea).]

Page 49

[image caption: Pressure testing in 1976 of a geothermal well drilled into 
Kilauea's lower east rift zone. This well currently produces three 
megawatts of electricity. (Photograph courtesy of the Hawaii Geothermal 
Project.) Below: Sugar cane thrives in the fertile volcanic soils derived 
from products of past Hawaiian eruptions. Mauna Kea Volcano is seen in the 
distance. (Photograph by Robert I. Tilling.)]


Volcanic Benefits

First of all, the Hawaiian Islands would not exist were it not for 
volcanic activity. Equally important, many factors that combine to make 
the islands an attractive place to live or visit depend directly or 
indirectly on the results of past and present eruptions.

Given enough rainfall, areas buried by new lava recover quickly; 
revegetation can begin less than 1 year after the eruption. Erosion and 
breakdown of the volcanic material can form fertile soils over periods of 
tens to thousands of years. These rich soils fostered the agricultural 
development of the Hawaiian Islands, as represented principally by the 
sugar, pineapple, coffee, and macadamia nut industries. Some of the 
volcanic products provide an abundant local source of raw materials for 
landscaping, housing and construction, and road building. In recent years, 
volcanic energy has been harnessed by a geothermal power plant on 
Kilauea's east rift zone; the three megawatts of electricity produced are 
fed into the grid of the local utility company. Much larger capacity 
geothermal development is under discussion.

Hawaii's majestic volcanic mountains, beautiful beaches, and pleasant 
climate combine to make the islands a popular tourist attraction, which 
includes two heavily visited national parks. Haleakala National Park on 
Maui, founded in 1961, features the spectacularly eroded summit crater of 
10,023 foot-high Haleakala Volcano, active as recently as about 1790. 
Hawaii Volcanoes National Park, created by Congress in 1916, contains the 
two currently active Hawaiian volcanoes, Mauna Loa and Kilauea. This park 
is one of the few places in the world where the processes and products of 
active volcanism can be viewed safely and comfortably by the nonspecialist 
and volcanologist alike. Indeed, millions of park visitors have 
experienced "live" the sights, sounds, and smells of volcanic eruptions 
and gained a firsthand appreciation of the phenomena that created and 
shaped these beautiful islands. 
 
Page 51

Benefits of Research at the Hawaiian Volcano Observatory

Hawaii is both a natural laboratory for the study of eruptive phenomena 
and a volcanic wonderland for visitors. The challenge facing scientists 
and government officials is clear: to reduce the adverse impact of 
eruptions in the short term, so that the residents and tourists in Hawaii 
can continue to enjoy the long-term benefits of volcanism. Toward this 
end, the Hawaiian Volcano Observatory (HVO) will continue to give timely 
warnings of anticipated volcanic activity, reliable and current progress 
reports on an eruption once it starts, and the best possible technical 
information on volcanic hazards posed by any eruption, present or future. 
In addition, the high eruption frequency of its volcanoes and the 
availability of state-of-the-art research facilities at HVO combine to 
make Hawaii an excellent training ground for volcanologists from around 
the world. HVO and other scientists are striving to improve volcano-
monitoring and eruption- forecasting techniques, in order to reduce the 
risks associated with eruptions of active volcanoes in Hawaii and 
elsewhere. 

[image caption: Above: Visitors on the rim of Mauna Ulu crater, 
silhouetted against the dusky sky (upper right), observe an active lava 
lake sloshing a few tens of feet below them. Below: Park visitors safely 
watch spectacular lava cascades and "curtains of fire" during the August 
1971 eruption at Kilauea's summit. Photographs courtesy of the National 
Park Service.)]

Page 52

Selected Readings

These works cited furnish additional information on topics not covered, or 
only briefly discussed, in the booklet.

Armstrong, R.W., 1983, editor, Atlas of Hawaii (Second Edition): 
University of Hawaii Press, Honolulu, 238 p. (A very handy reference 
volume compiled by the Department of Geography, University of Hawaii, 
describing the natural, cultural, and social environment of Hawaii, the 
50th State.) 

Brantley, Steven, and Topinka, Lyn, 1984, Volcanic studies at the U.S. 
Geological Survey's David A. Johnston Cascades Volcano Observatory, 
Vancouver, Washington: Earthquake Information Bulletin, v. 16, no. 2, p. 
41-120. (A well-illustrated report of the activities and workings of the 
Observatory, which was established in 1981 as a sister volcano observatory 
to the Hawaiian Volcano Observatory (see Heliker and others, 1986).) 

Dalrymple, G.B., Silver, E.l., and Jackson, E.D., 1973, Origin of the 
Hawaiian Islands: American Scientist, v. 61, no. 3, p. 294-308. (One of 
the best and most readable summaries of the "hotspot" hypothesis for the 
origin of the Hawaiian Ridge-Emperor Seamount Chain.) 

Decker, Robert, and Decker, Barbara, 1981, Volcanoes: W.H. Freeman and 
Company, San Francisco, 244 p. (An information-packed introduction to the 
study of volcanoes written in an easy-to-read style.) Decker, R.W., 
Wright, T.L., and Stauffer, P.H., 1987, editors, Volcanism in Hawaii: U.S. 
Geological Survey Professional Paper 1350, 1,667 p. (This two-volume set 
represents the most comprehensive collection of multidisciplinary 
scientific articles on Hawaiian volcanism available to date, containing 65 
reports.)

Duffield, W.A., 1972, A naturally occurring model of global plate 
tectonics: Journal of Geophysical Research, v. 77, no. 14, p. 2543-2555. 
(The first technical article to draw some interesting analogies between 
the movements of the crust of an active lava lake with much larger scale 
movements of the Earth's tectonic plates.) 

Eaton, J.P, and Murata, K.J., 1960, How volcanoes grow: Science, v. 132, 
p. 925-938. (The classic scientific article that presented the first 
comprehensive model for the workings of Hawaiian volcanoes, incorporating 
the results of modern volcano monitoring by the Hawaiian Volcano 
Observatory.) 

Editors, 1982, Volcano: in the series Planet Earth, Time-Life Books, 
Alexandria, Virginia, 176 p. (A well illustrated and readable general 
survey of volcanoes and their activity.) 

Heliker, Christina, Griggs, J.D., Takahashi, T.J., and Wright, T.L., 1986, 
Volcano monitoring at the U.S. Geological Survey's Hawaiian Volcano 
Observatory: Earthquakes and Volcanoes (formerly Earthquake Information 
Bulletin), v. 18, no. 1, 72 p. (An informative and richly illustrated 
article on the monitoring and research activities of the Observatory that 
was founded in 1912.) 

Lipman, P.W., and Mullineaux, D.R., editors, 1981, The 1980 eruptions of 
Mount St. Helens, Washington: U.S. Geological Survey Professional Paper 
1250, 844 p. (The most comprehensive collection of scientific articles on 
Mount St. Helens available to date; it contains 62 reports on many aspects 
of the 1980 eruptions of this best-known U.S. explosive volcano. This 
volume provides an instructive comparison with U.S. Geological Survey 
Professional Paper 1350, edited by Decker and others, which summarizes 
present knowledge on Hawaiian volcanoes, the best-known U.S. nonexplosive 
volcanoes.)

Page 53

Macdonald, G.A., Abbott, A.T., and Peterson, F.L., 1983 (Second Edition), 
Volcanoes in the sea: The geology of Hawaii: University of Hawaii Press, 
Honolulu, 517 p. (A handsome book that provides the best overview of the 
eruptive and other geologic processes that have shaped the Hawaiian 
Islands.) 

Peck, D.L., Wright, T.L., and Decker, R.W., 1979, The lava lakes of 
Kilauea: Scientific American, v. 241, no. 4, p.114-128. (An excellent 
summary of the methods and scientific results of drilling of Kilauea's 
molten lava lakes, which are natural laboratories for studying the cooling 
and crystallization of Hawaiian magma.) 

Tilling, R.l., 1982, Volcanoes: U.S. Geological Survey series of general-
interest publications, 46 p. (A general introduction for the nonspecialist 
to the study of volcanoes, with focus on the nature, types, workings, 
products, and hazards of volcanoes.) 

Tilling, R.l., 1984, Monitoring active volcanoes: U.S. Geological Survey 
series of general-interest publications, 13 p. (A generalized introduction 
to the common techniques of volcano monitoring, with a brief commentary on 
some eruptions during the 1975-1982 period, including Mauna Loa, Kilauea, 
Mount St. Helens, and El Chichon [Mexico].) 

Tilling, R.l., 1984, Eruptions of Mount St. Helens: Past, present, and 
future: U.S. Geological Survey series of general-interest publications, 46 
p. (A nontechnical summary, illustrated by many color photographs and 
diagrams, of the abundant scientific data available for the volcano, with 
emphasis on the catastrophic eruption of May 18, 1980, which caused the 
worst volcanic disaster in U.S. history.) 

Westervelt, W.D., 1963, Hawaiian legends of volcanoes: Charles E. Tuttle 
Company, Rutland, Vermont, 205 p. (An interesting collection of legends 
and stories about Pele, Hawaiian Goddess of Volcanoes, and her volcanic 
exploits and deeds.) 


Selected Viewings

The best way to see Hawaiian eruptive activity is to visit Hawaii 
Volcanoes National Park -- at the right time and place. The next best 
thing is to view movies or videos of Hawaiian eruptions, some of which are 
listed here. Some school and public libraries might have them in their 
collections. 

Case History of a Volcano, National Educational Television, Film Service, 
Indiana University Audio-Visual Center, Bloomington, Indiana 47401. (A 
presentation of the methods used by scientists of the Hawaiian Volcano 
Observatory to study Hawaiian volcanoes.) 

Eruption of Kilauea, 1959-60, Modern Talking Picture Service, Inc., 5000 
Park Street North, St. Petersburg, Florida 33709. (This award-winning film 
contains spectacular footage of the highest lava fountains ever recorded 
and of the formation of Kilauea Iki lava lake.) 

Fire Mountain, Encyclopedia Britannica Educational Corporation, 425 North 
Michigan Avenue, Chicago, Illinois 60611. (Short but excellent film on the 
1969-71 Mauna Ulu eruption of Kilauea Volcano.) 

Fire Under the Sea -- The Origin of Pillow Lava, Moonlight Productions, 
2650 California Street, Apt. B, Mountain View, California 94040. (This 
film features the actual sights and sounds of underwater movement of red-
hot lava and formation of pillow lava, as filmed by SCUBA-diving 
scientists, during the 1969-74 Mauna Ulu eruptions of Kilauea.) 

Heartbeat of a Volcano, Encyclopedia Britannica Education Corporation, 425 
North Michigan Avenue, Chicago, Illinois 60611. (A case study of an 
eruption of Kilauea Volcano through the eyes of the scientists of the 
Hawaiian Volcano Observatory; it contains dramatic scenes of active lava 
tubes.) 
 
Page 54

River of Fire, Hawaii Natural History Association, Ltd., Hawaii Volcanoes 
National Park, Hawaii 96718. (A video cassette that documents the March-
April 1984 eruption of Mauna Loa Volcano and contains some of the best 
footage of Hawaiian lava flows ever filmed.) 

The 1955 Eruption of Kilauea Volcano, Hawaiian Islands, Modern Talking 
Picture Service, Inc., 5000 Park Street North, St. Petersburg, Florida 
33709. (A brief film that includes good footage of lava fountains, 
formation of cinder cones, and advance of lava flows into the Pacific 
Ocean.) 

Volcano -- The Birth of a Mountain, Encyclopedia Britannica Educational 
Corporation, 425 North Michigan Avenue, Chicago, Illinois 60611. (The 
photographic record of the formation of the 397-foot-high volcanic shield 
at Mauna Ulu during the 1969-74 eruption of Kilauea; features excellent 
lava-fountaining and lava-flow scenes.) 

As the Nation's principal conservation agency, the Department of the 
Interior has responsibility for most of our nationally owned public lands 
and natural and cultural resources. This includes fostering sound use of 
our land and water resources; protecting our fish, wildlife, and 
biological diversity; preserving the environmental and cultural values of 
our national parks and historical places; and providing for the enjoyment 
of life through outdoor recreation. The Department assesses our energy and 
mineral resources and works to ensure that their development is in the 
best interests of all our people by encouraging stewardship and citizen 
participation in their care. The Department also has a major 
responsibility for American Indian reservation communities and for people 
who live in island territories under U.S. administration.  

The English units used in this book can be converted to metric equivalents 
by using the approximate conersions given below: [omitted]

Page 55

[image caption: The Kona coast, western part of the Island of Hawaii, is 
well known for its spectacular tropical sunsets. (Photograph by Taeko Jane 
Takahashi.)]


Endnotes

About the Author

Born in Shanghai, China, Bob Tilling grew up in southern California (near 
San Diego). He received his BA from Pomona College, and a Ph.D. in geology 
from Yale University, before joining the U.S. Geological Survey (USGS) in 
1962. Dr. Tilling has worked as a volcanologist for nearly 25 years, 
beginning with his assignment in 1972 to the USGS' Hawaiian Volcano 
Observatory (HVO), becoming its Scientist-in-Charge in 1975. He later 
served (1976-81) as the Chief of the Office of Geochemistry and 
Geophysics, at USGS' headquarters in Reston, Virginia, and was in charge 
of the USGS studies before, during, and after the 18 May 1980 catastrophic 
eruption of Mount St. Helens. Thus, Bob is no stranger to hazardous 
impacts of plate tectonics.
 
Since "rotating back" to a research position in 1982, Dr. Tilling resumed 
his studies of eruptive phenomena and associated hazards in the U.S. and 
abroad. He has written many articles -- technical and general-interest-- 
and has served as an invited consultant to a number of foreign countries 
(e.g., Colombia, Ecuador, Iceland, Indonesia, and Mexico). In February 
1995, Bob agreed once again to accept a management position: Chief 
Scientist of the USGS Volcano Hazards Team, which is responsible for 
monitoring the active volcanoes in the U.S. and assessing their potential 
hazards. 

Since 1987, Bob has worked at the USGS' western regional center in Menlo 
Park, California; he resides with his wife, Susan, in the foothills of the 
nearby Santa Cruz Mountains. They have two grown daughters, Bobbi and 
Karen, living in the San Francisco Bay Area. When not studying volcanoes, 
Bob enjoys sculpting, hiking, playing racquetball, listening to music 
(classical and country), and tasting of fine wines. 


Ordering Information

This publication is one of a series of general interest publications 
prepared by the U.S. Geological Survey to provide information about the 
earth sciences, natural resources, and the environment. To obtain the 
paper version of this book or a catalog of additional titles in the series 
"General Interest Publications of the U.S. Geological Survey," write: 

USGS Information Services
Box 25286, Building 810
Denver Federal Center
Denver, CO 80225
303-202-4700; Fax 303-202-4693