Ironically, these volcanic soils and inviting terranes have attracted, and continue to attract, people to live on the flanks of volcanoes. Thus, as population density increases in regions of active or potentially active volcanoes, mankind must become increasingly aware of the hazards and learn not to "crowd" the volcanoes. People living in the shadow of volcanoes must live in harmony with them and expect, and should plan for, periodic violent unleashings of their pent-up energy.
This booklet presents a generalized summary of the nature, workings, products, and hazards of the common types of volcanoes around the world, along with a brief introduction to the techniques of volcano monitoring and research.
On August 24, A.D. 79, Vesuvius Volcano suddenly exploded and destroyed the Roman cities of Pompeii and Herculaneum. Although Vesuvius had shown stir-rings of life when a succession`of earthquakes in A.D. 63 caused some damage, it had been literally quiet for hundreds of years and was considered "extinct." Its surface and crater were green and covered with vegetation, so the eruption was totally unexpected. Yet in a few hours, hot volcanic ash and dust buried the two cities so thoroughly that their ruins were not uncovered for nearly 1,700 years, when the discovery of an outer wall in 1748 started a period of modern archeology. Vesuvius has continued its activity intermittently ever since A.D 79 with numerous minor eruptions and several major eruptions occurring in 1631, 1794, 1872, 1906 and in 1944 in the midst of the Italian campaign of World War II.
In the United States on March 27, 1980, Mount St. Helens Volcano in the Cascade Range, southwestern Washington, reawakened after more than a century of dormancy and provided a dramatic and tragic reminder that there are active volcanoes in the "lower 48" States as well as in Hawaii and Alaska.The catastrophic eruption of Mount St. Helens on May 18, 1980, and related mudflows and flooding caused significant loss of life (57 dead or missing) and property damage over $1.2 billion). Mount St. Helens is expected to remain intermittently active for months or years, possibly even decades.
The word volcano comes from the little island of Vulcano in the Mediterranean Sea off
Sicily. Centuries ago, the people living in this area believed that Vulcano was the
chimney of the forge of Vulcan--the blacksmith of the Roman gods. They thought that
the hot lava fragments and clouds of dust erupting from Vulcano came from Vulcan's
forge as he beat out thunderbolts for Jupiter, king of the gods, and weapons for Mars,
the god of war. In Polynesia the people attributed eruptive activity to the beautiful but
wrathful Pele, Goddess of Volcanoes, whenever she was angry or spiteful. Today we
know that volcanic eruptions are not super natural but can be studied and interpreted
Driven by buoyancy and gas pressure the molten rock, which is lighter than the surrounding solid rock forces its way upward and may ultimately break though zones of weaknesses in the Earth's crust. If so, an eruption begins, and the molten rock may pour from the vent as non-explosive lava flows, or if may shoot violently into the air as dense clouds of lava fragments. Larger fragments fall back around the vent, and accumulations of fall-back fragments may move downslope as ash flows under the force of gravity. Some of the finer ejected materiaIs may be carried by the wind only to fall to the ground many miles away. The finest ash particles may be injected miles into the atmosphere and carried many times around the world by stratospheric winds before settling out.
Molten rock below the surface of the Earth that rises in volcanic vents is known as magma, but after it erupts from a volcano it is called lava. Originating many tens of miles beneath the ground, the ascending magma commonly contains some crystals, fragments of surrounding (unmelted) rocks, and dissolved gases, but it is primarily a liquid composed principally of oxygen, silicon, aluminum, iron, magnesium, calcium, sodium, potassium, titanium, and manganese. Magmas also contain many other chemical elements in trace quantities. Upon cooling, the liquid magma may precipitate crystals of various minerals until solidification is complete to form an igneous or magmatic rock.
The diagram below shows that heat concentrated in the Earth's upper mantle raises temperatures sufficiently to melt the rock locally by fusing the materials with the lowest melting temperatures, resulting in small, isolated blobs of magma. These blobs then collect, rise through conduits and fractures, and some ultimately may re-collect in larger pockets or reservoirs ("holding tanks") a few miles beneath the Earth's surface. Mounting pressure within the reservoir may drive the magma further upward through structurally weak zones to erupt as lava at the surface. In a continental environment, magmas are generated in the Earth's crust as well as at varying depths in the upper mantle. The variety of molten rocks in the crust, plus the possibility of mixing with molten materials from the underlying mantle, leads to the production of magmas with widely different chemical compositions.
If magmas cool rapidly, as might be expected near or on the Earth's surface, they solidify to form igneous rocks that are finely crystalline or glassy with few crystals. Accordingly, lavas, which of course are very rapidly cooled, form volcanic rocks typically characterized by a small percentage of crystals or fragments set in a matrix of glass (quenched or super-cooled magma) or finer grained crystalline materials. If magmas never breach the surface to erupt and remain deep underground, they cool much more slowly and thus allow ample time to sustain crystal precipitation and growth, resulting in the formation of coarser grained, nearly completely crystalline, igneous rocks. Subsequent to final crystallization and solidification, such rocks can be exhumed by erosion many thousands or millions of years later and be exposed as large bodies of so-called granitic rocks, as, for example, those spectacularly displayed in Yosemite National Park and other parts of the majestic Sierra Nevada mountains of California.
Lava is red hot when it pours or blasts out of a vent but soon changes to dark red, gray, black, or some other color as it cools and solidifies. Very hot, gas-rich lava containing abundant iron and magnesium is fluid and flows like hot tar, whereas cooler, gas-poor lava high in silicon, sodium, and potassium flows sluggishly, like thick honey in some cases or in others like pasty, blocky masses.
All magmas contain dissolved gases, and as they rise to the surface to erupt, the confining pressures are reduced and the dissolved gases are liberated either quietly or explosively. If the lava is a thin fluid (not viscous), the gases may escape easily. But if the lava is thick and pasty (highly viscous), the gases will not move freely but will build up tremendous pressure, and ultimately escape with explosive violence. Gases in lava may be compared with the gas in a bottle of a carbonated soft drink. If you put your thumb over the top of the bottle and shake it vigorously, the gas separates from the drink and forms bubbles. When you remove your thumb abruptly, there is a miniature explosion of gas and liquid. The gases in lava behave in somewhat the same way. Their sudden expansion causes the terrible explosions that throw out great masses of solid rock as well as lava, dust, and ashes.
The violent separation of gas from lava may produce rock froth called pumice. Some of
this froth is so light--because of the many gas bubbles--that it floats on water. In many
eruptions, the froth is shattered explosively into small fragments that are hurled high into
the air in the form of volcanic cinders (red or black), volcanic ash (commonly tan or
gray), and volcanic dust.
In 1943 a cinder cone started growing on a farm near the village of Parícutin in Mexico. Explosive eruptions caused by gas rapidly expanding and escaping from molten lava formed cinders that fell back around the vent, building up the cone to a height of 1,200 feet. The last explosive eruption left a funnel-shaped crater at the top of the cone. After the excess gases had largely dissipated, the molten rock quietly poured out on the surrounding surface of the cone and moved downslope as lava flows. This order of events--eruption, formation of cone and crater, lava flow--is a common sequence in the formation of cinder cones.
During 9 years of activity, Parícutin built a prominent cone, covered about 100 square
miles with ashes, and destroyed the town of San Juan. Geologists from many parts of the
world studied Parícutin during its lifetime and learned a great deal about volcanism, its
products, and the modification of a volcanic landform by erosion.
Most composite volcanoes have a crater at the summit which contains a central vent or a clustered group of vents. Lavas either flow through breaks in the crater wall or issue from fissures on the flanks of the cone. Lava, solidified within the fissures, forms dikes that act as ribs which greatly strengthen the cone.
The essential feature of a composite volcano is a conduit system through which magma from a reservoir deep in the Earth's crust rises to the surface. The volcano is built up by the accumulation of material erupted through the conduit and increases in size as lava, cinders, ash, etc., are added to its slopes.
When a composite volcano becomes dormant, erosion begins to destroy the cone. As the cone is stripped away, the hardened magma filling the conduit (the volcanic plug) and fissures (the dikes) becomes exposed, and it too is slowly reduced by erosion. Finally, all that remains is the plug and dike complex projecting above the land surface--a telltale remnant of the vanished volcano.
An interesting variation of a composite volcano can be seen at Crater Lake in Oregon.
From what geologists can interpret of its past, a high volcano--called Mount Mazama-
probably similar in appearance to present-day Mount Rainier was once located at this
spot. Following a series of tremendous explosions about 6,800 years ago, the volcano
lost its top. Enormous volumes of volcanic ash and dust were expelled and swept down
the slopes as ash flows and avalanches. These large-volume explosions rapidly drained
the lava beneath the mountain and weakened the upper part. The top then collapsed to
form a large depression, which later filled with water and is now completely occupied by
beautiful Crater Lake. A last gasp of eruptions produced a small cinder cone, which rises
above the water surface as Wizard Island near the rim of the lake. Depressions such as
Crater Lake, formed by collapse of volcanoes, are known as calderas. They are usually
large, steep-walled, basin-shaped depressions formed by the collapse of a large area over,
and around, a volcanic vent or vents. Calderas range in form and size from roughly
circular depressions 1 to 15 miles in diameter to huge elongated depressions as much as
60 miles long.
In some eruptions, basaltic lava pours out quietly from long fissures instead of central
vents and floods the surrounding countryside with lava flow upon lava flow, forming
broad plateaus. Lava plateaus of this type can be seen in Iceland, southeastern
Washington, eastern Oregon, and southern Idaho. Along the Snake River in Idaho, and
the Columbia River in Washington and Oregon, these lava flows are beautifully exposed
and measure more than a mile in total thickness.
Only two men survived; one because he was in a poorly ventilated, dungeon-like jail cell
and the other who somehow made his way safely through the burning city.
Volcanic plugs are believed to overlie a body of magma which could be either still
largely liquid or completely solid depending on the state of activity of the volcano.
Plugs are known, or postulated, to be commonly funnel shaped and to taper downward
into bodies increasingly elliptical in plan or elongated to dike-like forms. Typically,
volcanic plugs and necks tend to be more resistant to erosion than their enclosing rock
formations. Thus, after the volcano becomes inactive and deeply eroded, the exhumed
plug may stand up in bold relief as an irregular, columnar structure. One of the best
known and most spectacular diatremes in the United States is Ship Rock in New
Mexico, which towers some 1,700 feet above the more deeply eroded surrounding
plains. Volcanic plugs, including diatremes, are found elsewhere in the western United
States and also in Germany, South Africa, Tanzania, and Siberia.
Maars occur in the western United States, in the Eifel region of Germany, and in other
geologically young volcanic regions of the world. An excellent example of a maar is
Zuni Salt Lake in New Mexico, a shallow saline lake that occupies a flat-floored crater
about 6,500 feet across and 400 feet deep. Its low rim is composed of loose pieces of
basaltic lava and wallrocks (sandstone, shale, limestone) of the underlying diatreme, as
well as random chunks of ancient crystalline rocks blasted upward from great depths.
Other possible explanations for these nonvolcanic craters include subsurface salt-dome intrusion (and subsequent dissolution and collapse caused by subsurface limestone dissolution and/or ground-water withdrawal; and collapse related to melting of glacial ice. An impressive example of an impact structure is Meteor Crater, Ariz., which is visited by thousands of tourists each year. This impact crater, 4,000 feet in diameter and 600 feet deep, was formed in the geologic past (probably 30,00050,000 years before present) by a meteorite striking the Earth at a speed of many thousands of miles per hour.
In addition to Meteor Crater, very fresh, morphologically distinct, impact craters are
found at three sites near Odessa, Tex., as well as 10 or 12 other locations in the world. Of
the more deeply eroded, less obvious, postulated impact structures, there are about ten
well-established sites in the United States and perhaps 80 or ~0 elsewhere in the world.
The type of volcanic eruption Is often labeled with the name of a well-known volcano where characteristic behavior is similar--hence the use of such terms as "Strombolian," "Vulcanian," "Vesuvian," "Pelean," "Hawaiian," and others. Some volcanoes may exhibit only one characteristic type of eruption during an interval of activity--others may display an entire sequence of types.
In a Strombolian-type eruption observed during the 1965 activity of Irazu Volcano in Costa Rica, huge clots of molten lava burst from the summit crater to form luminous arcs through the sky. Collecting on the flanks of the cone, lava clots combined to stream down the slopes in fiery rivulets.
In contrast, the eruptive activity of Parícutin Volcano in 1947 demonstrated a "Vulcanian"-type eruption, in which a dense cloud of ash-laden gas explodes from the crater and rises high above the peak. Steaming ash forms a whitish cloud near the upper level of the cone.
In a "Vesuvian" eruption, as typified by the eruption of Mount Vesuvius in Italy in A.D. 79, great quantities of ash-laden gas are violently discharged to form cauliflower-shaped cloud high above the volcano.
In a "Peléan" or "Nuée Ardente (glowing cloud) eruption, such as occurred on the Mayon Volcano in the Philippines in 1968, a large quantity of gas, dust, ash, and incandescent lava fragments are blown out of a central crater, fall back, and form tongue-like, glowing avalanches that move downslope at velocities as great as 100 miles per hour. Such eruptive activity can cause great destruction and loss of life if it occurs in populated areas, as demonstrated by the devastation of St. Pierre during the 1902 eruption of Mont Pelée on Martinique, Lesser Antilles.
"Hawaiian" eruptions may occur along fissures or fractures that serve as linear vents, such as during the eruption of Mauna Loa Volcano in Hawaii in 1950; or they may occur at a central vent such as during the 1959 eruption in Kilauea Iki Crater of Kilauea Volcano, Hawaii. In fissure-type eruptions, molten, incandescent lava spurts from a fissure on the volcano's rift zone and feeds lava streams that flow downslope. In central-vent eruptions, a fountain of fiery lava spurts to a height of several hundred feet or more. Such lava may collect in old pit craters to form lava lakes, or form cones, or feed radiating flows.
"Phreatic" (or steam-blast) eruptions are driven by explosive expanding steam resulting from cold ground or surface water coming into contact with hot rock or magma. The distinguishing feature of phreatic explosions is that they only blast out fragments of preexisting solid rock from the volcanic conduit; no new magma is erupted. Phreatic activity is generally weak, but can be quite violent in some cases, such as the 1965 eruption of Taal Volcano, Philippines, and the 1975-76 activity at La Soufrière, Guadeloupe (Lesser Antilles).
The most powerful eruptions are called "plinian" and involve the explosive ejection of
relatively viscous lava. Large plinian eruptions--such as during 18 May 1980 at Mount
St. Helens or, more recently, during 15 June 1991 at Pinatubo in the Philippines--can
send ash and volcanic gas tens of miles into the air. The resulting ash fallout can affect
large areas hundreds of miles downwind. Fast-moving deadly pyroclastic flows ("nuées
ardentes") are also commonly associated with plinian eruptions.
The unlimited supply of water surrounding submarine volcanoes can cause them to behave differently from volcanoes on land. Violent, steam-blast eruptions take place when sea water pours into active shallow submarine vents. Lava, erupting onto a shallow sea floor or flowing into the sea from land, may cool so rapidly that it shatters into sand and rubble. The result is the production of huge amounts of fragmental volcanic debris. The famous "black sand" beaches of Hawaii were created virtually instantaneously by the violent interaction between hot lava and sea water. On the other hand, recent observations made from deep-diving submersibles have shown that some submarine eruptions produce flows and other volcanic structures remarkably similar to those formed on land. Recent studies have revealed the presence of spectacular, high temperature hydrothermal plumes and vents (called "smokers") along some parts of the mid-oceanic volcanic rift systems. However, to date, no direct observation has been made of a deep submarine eruption In progress.
During an explosive submarine eruption in the shallow open ocean, enormous piles of
debris are built up around the active volcanic vent. Ocean currents rework the debris in
shallow water, while other debris slumps from the upper part of the cone and flows into
deep water along the sea floor. Fine debris and ash in the eruptive plume are scattered
over a wide area in airborne clouds. Coarse debris in the same eruptive plume rains into
the sea and settles on the flanks of the cone. Pumice from the eruption floats on the
water and drifts with the ocean currents over a large area.
Erupting geysers provide spectacular displays of underground energy suddenly unleashed, but their mechanisms are not completely understood. Large amounts of hot water are presumed to fill underground cavities. The water, upon further heating, is violently ejected when a portion of it suddenly flashes into steam. This cycle can be repeated with remarkable regularity, as for example, at Old Faithful Geyser in Yellowstone National Park, which erupts on an average of about once every 65 minutes.
Fumaroles, which emit mixtures of steam and other gases, are fed by conduits that pass through the water table before reaching the surface of the ground. Hydrogen sulfide (H2S), one of the typical gases issuing from fumaroles, readily oxidizes to sulfuric acid and native sulfur. This accounts for the intense chemical activity and brightly colored rocks in many thermal areas.
Hot springs occur in many thermal areas where the surface of the Earth intersects the
water table. The temperature and rate of discharge of hot springs depend on factors such
as the rate at which water circulates through the system of underground channelways,
the amount of heat supplied at depth, and the extent of dilution of the heated water by
cool ground water near the surface.
Many volcanoes are in and around the Mediterranean Sea. Mount Etna in Sicily is the largest and hiqhest of these mountains. Italy's Vesuvius is the only active volcano on the European mainland. Near the island of Vulcano, the volcano Stromboli has been in a state of nearly continuous, mild eruption since early Roman times. At night, sailors in the Mediterranean can see the glow from the fiery molten material that is hurled into the air. Very appropriately, Stromboli has been called "the lighthouse of the Mediterranean.
Some volcanoes crown island areas lying near the continents, and others form chains of islands in the deep ocean basins. Volcanoes tend to cluster along narrow mountainous belts where folding and fracturing of the rocks provide channelways to the surface for the escape of magma. Significantly, major earthquakes also occur along these belts, indicating that volcanism and seismic activity are often closely related, responding to the same dynamic Earth forces.
In a typical "island-arc" environment, volcanoes lie along the crest of an arcuate, crustal ridge bounded on its convex side by a deep oceanic trench. The granite or granitelike layer of the continental crust extends beneath the ridge to the vicinity of the trench. Basaltic magmas, generated in the mantle beneath the ridge, rise along fractures through the granitic layer. These magmas commonly will be modified or changed in composition during passage through the granitic layer and erupt on the surface to form volcanoes built largely of nonbasaltic rocks.
In a typical "oceanic" environment, volcanoes are alined along the crest of a broad ridge that marks an active fracture system in the oceanic crust. Basaltic magmas, generated in the upper mantle beneath the ridge, rise along fractures through the basaltic layer. Because the granitic crustal layer is absent, the magmas are not appreciably modified or changed in composition and they erupt on the surface to form basaltic volcanoes.
In the typical "continental" environment, volcanoes are located unstable, mountainous
belts that have thick roots of granite or granitelike rock. Magmas, generated near the
base of the mountain root, rise slowly or intermittently along fractures in the crust.
During passage through the granitic layer, magmas are commonly modified or changed
in composition and erupt on the surface to form volcanoes constructed of nonbasaltic
The accompanying figure shows the boundaries of lithosphere plates that are presently
active. The double lines indicate zones of spreading from which plates are moving apart.
The lines with barbs show zones of underthrusting (subduction), where one plate is
sliding beneath another. The barbs on the lines indicate the overriding plate. The single
line defines a strike-slip fault along which plates are sliding horizontally past one
another. The stippled areas indicate a part of a continent, exclusive of that along a plate
boundary, which is undergoing active extensional, compressional, or strike-slip faulting.
From the 1976-1979 Viking mission, scientists have been able to study the volcanoes on Mars, and their studies are very revealing when compared with those of volcanoes on Earth. For example, Martian and Hawaiian volcanoes closely resemble each other in form. Both are shield volcanoes, have gently sloping flanks, large multiple collapse pits at their centers, and appear to be built of fluid lavas that have left numerous flow features on their flanks. The most obvious difference between the two is size. The Martian shields are enormous. They can grow to over 17 miles in height and more than 350 miles across, in contrast to a maximum height of about 6 miles and width of 74 miles for the Hawaiian shields.
Voyager-2 spacecraft images taken of lo, a moon of Jupiter, captured volcanoes in the
actual process of eruption. The volcanic plumes shown on the image rise some 60 to 100
miles above the surface of the moon. Thus, active volcanism is taking place, at present,
on at least one planetary body in addition to our Earth.
Perhaps "modern" volcanology began in 1912, when Thomas A. Jaggar, Head of the Geology Department of the Massachusetts Institute of Technology, founded the Hawaiian Volcano Observatory (HVO), located on the rim of Kilauea's caldera. Initially supported by an association of Honolulu businessmen, HVO began to conduct systematic and continuous monitoring of seismic activity preceding, accompanying, and following eruptions, as well as a wide variety of other geological, geophysical, and geochemical observations and investigations. Between 1919 and 1948, HVO was administered by various Federal agencies (National Weather Service, U.S. Geological Survey, and National Park Service), and since 1948 it has been operated continuously by the Geological Survey as part of its Volcano Hazards Program. The more than 75 years of comprehensive investigations by HVO and other scientists in Hawaii have added substantially to our understanding of the eruptive mechanisms of Kilauea and Mauna Loa, two of the world's most active volcanoes. Moreover, the Hawaiian Volcano Observatory pioneered and refined most of the commonly used volcano-monitoring techniques presently employed by other observatories monitoring active volcanoes elsewhere, principally in Indonesia, Italy, Japan, Latin America, New Zealand, Lesser Antilles (Caribbean), Philippines, and Kamchatka (U .S.S.R.).
What does "volcano monitoring" actually involve? Basically, it is the keeping of a detailed "diary" of the changes--visible and invisible--in a volcano and its surroundings. Between eruptions, visible changes of importance to the scientists would include marked increase or decrease of steaming from known vents; emergence of new steaming areas; development of new ground cracks or widening of old ones; unusual or inexplicable withering of plant life; changes in the color of mineral deposits encrusting fumaroles; and any other directly observable, and often measurable, feature that might reflect a change in the state of the volcano. Of course, the "diary" keeping during eruptive activity presents additional tasks. Wherever and whenever they can do so safely, scientists document, in words and on film, the course of the eruption in detail; make temperature measurements of lava and gas; collect the eruptive products and gases for subsequent laboratory analysis; measure the heights of lava fountains or ash plumes; gage the flow rate of ash ejection or lava flows; and carry out other necessary observations and measurements to fully document and characterize the eruption. For each eruption, such documentation and data collection and analysis provide another building block in constructing a model of the characteristic behavior of a given volcano or type of eruption.
Volcano monitoring also involves the recording and analysis of volcanic phenomena not visible to the human eye, but measurable by precise and sophisticated instruments. These phenomena include ground movements, earthquakes (particularly those too small to be felt by people), variations in gas compositions, and deviations in local electrical and magnetic fields that respond to pressure and stresses caused by the subterranean magma movements.
Some common methods used to study invisible, volcano-related phenomena are based on:
A strikingly successful example of volcano research and volcanic hazard assessment was the 1978 publication (Bulletin 1383-C) by two Geological Survey scientists, Dwight Crandell and Donal Mullineaux, who concluded that Mount St. Helens was the Cascade volcano most frequently active in the past 4,500 years and the one most likely to reawaken to erupt, "...perhaps before the end of this century." Their prediction came true when Mount St. Helens rumbled back to life in March of 1980. Intermittent explosions of ash and steam and periodic formation of short-lived lava domes continued throughout the decade. Analysis of the volcano's past behavior indicates that this kind of eruptive activity may continue for years or decades, but another catastrophic eruption like that of May 18, 1980, is unlikely to occur soon.
On 18 May 1982, the U.S. Geological Survey (USGS) formally dedicated the David A.
Johnston Cascades Volcano Observatory (CVO) in Vancouver, Washington, in memory
of the Survey volcanologist killed two years earlier. This facility--a sister observatory to
the Hawaiian Volcano Observatory-- facilitates the increased monitoring and research on
not only Mount St. Helens but also the other volcanoes of the Cascade Range of the
Pacific Northwest. More recently, in cooperation with the State of Alaska, the USGS
established the Alaska Volcano Observatory in March 1988. The work being done at
these volcano observatories provides important comparisons and contrasts between the
behavior of the generally non-explosive Hawaiian shield volcanoes and that of the
generally explosive composite volcanoes of the Cascade and Alaskan
The challenge to scientists involved with volcano research is to mitigate the short-term
adverse impacts of eruptions, so that society may continue to enjoy the long-term
benefits of volcanism. They must continue to improve the capability for predicting
eruptions and to provide decision makers and the general public with the best possible
information on high-risk volcanoes for sound decisions on land-use planning and public
safety. Geoscientists still do not fully understand how volcanoes really work, but
considerable advances have been made in recent decades. An improved understanding
of volcanic phenomena provides important clues to the Earth's past, present, and
possibly its future.
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Harris, S.L., 1988, Fire mountains of the West: The Cascade and Mono Lake Volcanoes: Missoula, Montana, Mountain Press Publishing Company, 379 p.
Heliker, Christina, 1990, Volcanic and seismic hazards on the Island of Hawaii: Reston, Virginia, U.S. Geological Survey, 48 p.
Macdonald, G.A., 1972, Volcanoes: Englewood Cliffs, New Jersey, Prentice-Hall, Inc., 510 p.
Simkin, Tom, Tilling, R.l., Taggart, J.N., Jones, W.J., and Spall, Henry, compilers, 1989, This dynamic planet: World Map of volcanoes, earthquakes, and plate tectonics: U.S. Geological Survey, Reston, Virginia, prepared in cooperation with the Smithsonian Institution, Washington, D.C. (scale 1 :30,000,000 at equator).
Tilling, R.l., Heliker, Christina, and Wright, T.L., 1989, Eruptions of Hawaiian volcanoes: Past, present, and future: Reston, Virginia, U.S. Geological Survey, 54 p.
Tilling, R.l., Topinka, Lyn, and Swanson, D.A., 1990, Eruptions of Mount St. Helens: Past, present, and future: Reston, Virginia, U.S. Geological Survey, 56 p. (Revised edition).
Tilling, R.l., 1991, Monitoring active volcanoes: Reston, Virginia, U.S. Geological Survey, 13 p. (Revised edition).
Wood, C.A., and Kienle, Jurgen, 1990, Volcanoes of North America: United States and
Canada: New York, Cambridge University Press, 354 p.