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Terrestrial Volcanoes

By turns hot embers from her entrails fly,
And flakes of mountain flame that arch the sky.
-Virgil's Aeneid


Table of Contents 
   Movies of Volcanoes 
   Views of Terrestrial Volcanoes 
The Nature of Volcanoes 
Principal Types of Volcanoes 
Hawaiian Volcanoes 
Resurgent Calderas and the
   Valles Caldera
Additional Images & Animations 
Internet Resources 
USGS Volcano Hazards 
Volcano World Home Page 
EOS Volcanology 
Volcanoes destroy and volcanoes create. The catastrophic eruption of Mount St. Helens on May 18, 1980, made clear the awesome destructive power of a volcano. Yet, over a time span longer than human memory and record, volcanoes have played a key role in forming and modifying the planet upon which we live. More than 80 percent of the Earth's surface--above and below sea level--is of volcanic origin. Gaseous emissions from volcanic vents over hundreds of millions of years formed the Earth's earliest oceans and atmosphere, which supplied the ingredients vital to evolve and sustain life. Over geologic eons, countless volcanic eruptions have produced mountains, plateaus, and plains, which subsequent erosion and weathering have sculpted into majestic landscapes and formed fertile soils.

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.

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 by scientists. (Abstracted from Tillings)

The Nature of Volcanoes

Movies of Volcanoes

The following video clips are take from "Understanding Volcanic Hazards", © 1995, International Association of Volcanology and Chemistry of Earth's Interior (IAVCEI).

Views of Terrestrial Volcanoes

Isla Isabella
This is an image showing part of Isla Isabella in the western Galapagos Islands. The western Galapagos Islands, which lie about 1,200 kilometers (750 miles) west of Ecuador in the eastern Pacific, have six active volcanoes similar to the volcanoes found in Hawaii. These volcanoes reflect the volcanic processes that occur where the ocean floor is created. Since the time of Charles Darwin's visit to the area in 1835, there have been over 60 recorded eruptions on these volcanoes. This SIR-C/X-SAR image of Alcedo and Sierra Negra volcanoes shows the rougher lava flows as bright features, while ash deposits and smooth pahoehoe lava flows appear dark. A small portion of Isla Fernandina is visible in the extreme upper left corner of the image. (Courtesy NASA/JPL)

Isla Isabella in 3D
This is a three-dimensional view of Isabela, one of the Galapagos Islands located off the western coast of Ecuador, South America. (Courtesy NASA/JPL)

Galapagos Islands
This image of the Galapagos Islands was taken from the space shuttle using a hand held camera. There are seven shield volcanoes in this area (Fernandina, Ecuador, Wolf, Darwin, Alcedo, Sierra Negra, and Azul) which collectively have erupted more than sixty times this century. Unlike Hawaii, these volcanoes are infrequently studied due to their inaccessibility and delicate ecology. In addition, the rugged terrain, lack of water and field support make these volcanoes difficult to map and study in the field. (Courtesy NASA/JPL)

Mount Pinatubo
This is a false color image of the area around Mount Pinatubo in the Philippines. The area shown is approximately 45 by 68 kilometers (28 by 42 miles). The main volcanic crater on Mount Pinatubo produced by the June 1991 eruptions, and the steep slopes on the upper flanks of the volcano, are easily seen in this image. The red color on the high slopes show the rougher ash deposited during the 1991 eruption. The dark drainages are the smooth mudflows which continue to flood the river valleys after heavy rain.

The 1991 eruption of Mount Pinatubo in the Philippines is well known for its near-global effects on the atmosphere and climate due to the large amount of sulfur dioxide that it injected into the upper atmosphere. What is less widely known is that even today the volcano continues to be a major hazard to the people who have returned to the area around the volcano. Dangerous mudflows (called "lahars") are often generated by heavy rains, and these can still sweep down river valleys and wash out roads and villages, or bury low lying areas in several meters of mud and volcanic debris. These mudflows will continue to be a severe hazard around Pinatubo for the next 10 to 15 years. (Courtesy NASA/JPL)

Virunga Volcano Chain
This is a false-color radar image of Central Africa, showing the Virunga volcano chain along the borders of Rwanda, Zaire, and Uganda. This area is home to the endangered mountain gorillas. The image was acquired on October 3, 1994.

The dark area at the top of the image is Lake Kivu, which forms the border between Zaire (to the right) and Rwanda (to the left). In the center of the image is the steep cone of Nyiragongo volcano, rising 3,465 meters (11,369 feet) high, with its central crater now occupied by a lava lake. To the left are three volcanoes, Mount Karisimbi, rising 4,500 meters (14,800 feet) high; Mount Sabinyo, rising 3,600 meters (12,000 feet) high; and Mount Muhavura, rising 4,100 meters (13,500 feet) high. To their right is Nyamuragira volcano, which is 3,053 meters (10,017 feet) tall, with radiating lava flows dating from the 1950s to the late 1980s. These active volcanoes constitute a hazard to the town of Goma, Zaire, and the nearby Rwandan refugee camps, located on the shore of Lake Kivu at the top left. (Courtesy NASA/JPL)

Mount Rainier, Washington
This is a radar image of Mount Rainier in Washington state. The volcano last erupted about 150 years ago and numerous large floods and debris flows have originated on its slopes during the last century. Today the volcano is heavily mantled with glaciers and snowfields. More than 100,000 people live on young volcanic mudflows less than 10,000 years old and, consequently, are within the range of future, devastating mudslides. North is toward the top left of the image. Forested regions are pale green in color; clear cuts and bare ground are bluish or purple; ice is dark green and white. The round cone at the center of the image is the 14,435-foot (4,399- meter) active volcano, Mount Rainier. On the lower slopes is a zone of rock ridges and rubble (purple to reddish) above coniferous forests (in yellow/green). (Courtesy NASA/JPL)

Kliuchevskio Volcano, Russia
This is an image of the area of Kliuchevskoi volcano, Kamchatka, Russia, which began to erupt on September 30, 1994. Kliuchevskoi is the blue triangular peak in the center of the image, toward the left edge of the bright red area that delineates bare snow cover. The image was acquired on October 5, 1994. It shows an area approximately 75 kilometers by 100 kilometers (46 miles by 62 miles) that is centered at 56.07 degrees north latitude and 160.84 degrees east longitude. North is toward the bottom of the image.

The Kamchatka volcanoes are among the most active volcanoes in the world. The volcanic zone sits above a tectonic plate boundary, where the Pacific plate is sinking beneath the northeast edge of the Eurasian plate. In addition to Kliuchevskoi, two other active volcanoes are visible in the image. Bezymianny, the circular crater above and to the right of Kliuchevskoi, contains a slowly growing lava dome. Tolbachik is the large volcano with a dark summit crater near the upper right edge of the red snow covered area. The Kamchatka River runs from right to left across the bottom of the image. The current eruption of Kliuchevskoi included massive ejections of gas, vapor and ash, which reached altitudes of 15,000 meters (50,000 feet). Melting snow mixed with volcanic ash triggered mudflows on the flanks of the volcano. Paths of these flows can be seen as thin lines in various shades of blue and green on the north flank in the center of the image. (Courtesy NASA/JPL)

Unzen Volcano, Japan
This is a space radar image of the area around the Unzen volcano, on the west coast of Kyushu Island in southwestern Japan. Unzen, which appears in this image as a large triangular peak with a white flank near the center of the peninsula, has been continuously active since a series of powerful eruptions began in 1991. The image was acquired on April 15, 1994. The image shows an area 41.5 kilometers by 32.8 kilometers (25.7 miles by 20.3 miles) that is centered at 32.75 degrees north latitude and 130.15 degrees east longitude. North is toward the upper left of the image. The city of Shimabara sits along the coast at the foot of Unzen on its east and northeast sides. At the summit of Unzen a dome of thick lava has been growing continuously since 1991. Collapses of the sides of this dome have generated deadly avalanches of hot gas and rock known as pyroclastic flows. (Courtesy NASA/JPL)


The introduction to this page along with The Nature of Volcanoes and Principal Types of Volcanoes was adapted from the U.S. Geological Survey's publication, Volcanoes, by Robert Tilling.




Copyright © 1997-1999 by Calvin J. Hamilton. All rights reserved.