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Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

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At least 55 records · Page 3Linked to original sources
USGS1990

The Pacific Northwest; linkage between earthquake and volcano hazards

AS the title of the magazine Earthquake and Volcanoes suggests, these two geological phenomena are often closely associated. Earthquakes frequently precede volcanic eruptions, and volcanoes are often sources of small to intermediate size earthquakes resulting from the movement of magma within the volcano's plumbing system. In the Pacific Northwest, the association between earthquakes and volcanoes is much more fundamental- they both arise from the same large-scale interaction between two plates of the Earth's crust. The oceanic Juan de Fuca plate is being shoved beneath the edge of the continental North American plate in the process known as subduction. The result is the Cascade chain of volcanoes, the potential for very large earthquakes along the coastal margin, and the generation of stresses that produce other regional earthquakes. The Pacific Northwest (Oregon, Washington, and northern California) is experiencing rapid industrial and population growth. The same conditions that make the region attractive- close proximity to both mountains and oceans, volcanoes and spectacular inland waters- also present significant geologic hazards that are easily overlooked in the normal timetable of human activities. The catastrophic eruption of Mount St. Helens 10 years ago serves as a dramatic reminder of the forces of nature that can be unleashed through volcanism. other volcanoes such as mount Rainier, a majestic symbol of Washington, or Mount hood in Oregon, lie closer to population centers and could present far greater hazards should they become active. Earthquakes may affect even larger regions, prodcuging more cumulative damage.

Pacific Northwest↗
USGS1988

Volcanology in Hawaii

Polynesians who first inhabited the Hawaiian Islands told in legend about Pele, Goddess of volcanic fires, who migrated from the Island of Kauai to Oahu, then to Maui, and finally to her present home in Kilauea Volcano's Halemaumau Crater on the Island of Hawaii. Geologists today accept this same relative age progressions for the evolution of the islands, demonstrating the kernels of geologic truth may lie in long-lived myths and legends. J.D. Dana, a geologist with a United states exploring expedition in the 1840's, was the first to write about the increase in age of the Hawaiian Islands to the northwest. He noted that weathering of the lavas, erosional destruction of the islands by waves and streams and the growth of reeds around the islands progressively increased away from the Island of Hawaii. He correctly established the islands' relative ages, but absolute ages had to wait for over 120 years until radioactive age-dating techniques became available.

Hawaii↗
USGS1991

Reducing volcanic risk

The last two decades have brought major advances in research on how volcanoes work and how to monitor their changing habits. Geologic mapping as well as studies of earthquake patterns and surface deformation associated with underground movement of magma have given scientists a better view of the inner structure and dynamics of active volcanoes. With the next decade, the time has come to focuses more on applying this knowledge toward reducing the risk from volcanic activity on a worldwide basis.

Earthquakes & Volcanoes (USGS)↗
USGS1991

Volcanic eruptions; energy and size

The Earth is a dynamic planet. Many different processes are continuously developing, creating a delicate balance between the energy stored and generated in its interior and the heat lost into space. The heat in continuously transferred through complex self-regulating convection mechanisms on a planetary scale. The distribution of terrestrial heat flow reveals some of the fine structure of the energy transport mechanisms in the outer layers of the Earth. Of these mechanisms in the outer layers of the Earth. Of these mechanisms, volcanism is indeed the most remarkable, for it allows energy to be transported in rapid bursts to the surface. In order to maintain the subtle balance of the terrestrial heat machine, one may expect that some law or principle restricts the ways in which these volcanic bursts affect the overall energy transfer of the Earth. For instance, we know that the geothermal flux of the planet amounts to 10 28 erg/year. On the other hand, a single large event like the Lava Creek Tuff eruption that formed Yellowstone caldera over half a million years ago may release the same amount of energy in a very small area, over a short period of time.

Earthquakes & Volcanoes (USGS)↗
USGS1992

Historical seismicity

The North Coast region of California in the vicinity of Cape Mendocino is one of the state's most seismically active areas, accounting for 25 percent of seismic energy release in California during the last 50 years. the region is located in a geologically dynamic are surrounding the Mendocino triple junction where three of the Earth's tectonic plates join together ( see preceding article by Sam Clarke). In the historic past the North Coast has been affected by earthquakes occurring on the San Andreas fault system to the south, the Mendocino fault to the southwest, and intraplate earthquakes within both the Gorda and North American plates. More than sixty of these earthquakes have caused damage since the mid-1800's. Recent studies indicate that California's North Coast is also at risk with respect to very large earthquakes (magnitude >8) originating along the Cascadia subduction zone. Although the subduction zone has not generated great earthquakes in historic time, paleoseismic evidence suggests that such earthquakes have been generated by the subduction zone in the recent prehistoric past.

California↗
USGS1993

Damages from the 20 September earthquakes near Klamath Falls, Oregon

The Klamath Falls earthquakes of 8:28PM PDT (magnitude 5.9) and 10:45 PM PDT (magnitude 6.0) on September 20, 1993, were felt over an area of about 130,000 sq km in southwestern Oregon and northern California. Losses due to property damage are preliminary estimated to be about 7.5 million. A motorist died when the car he was driving was crushed by a boulder in an earthquake-induced rockfall, and an elderly woman died of a heart attack that was apparently triggered by one of the earthquakes. Most of the damage resulting from the earthquakes was reported from Klamath Falls, approximately 20 km from the source region of earthquakes. As has commonly been the case with earthquakes in other parts of the United States, the degree of damage was highly uneven in Klamath Falls. Most of the town escaped with little damage to buildings or building contents. Losses were concentrated in the downtown area, but even there most of the buildings were not damaged. The unevenness of damage in earthquakes results primarily from large differences in the seismic resistance of individual buildings and differences in the seismic response due to different soil conditions and geology beneath buildings.

Oregon↗
USGS1990

Historical activity at Campi Flegrei caldera, southern Italy

According to the biography of the 6th century Italian lawyer Antonion Castaldo, the swarm of earthquakes that had bothered the inhabitants of Pozzuoli and Naples all summer long ended abruptly on the eve of St. Michael (September 29) in the year 1538. Castaldo recalled that the end of this swarm was heralded by a very large earthquake followed immediately by loud thunder, sounding like bombardment from heavy guns. This was the beginning of a week-long eruption in Campi Flegrei, a volcanic caldera located along the west coast of southern Italy near Naples. This event has been the only eruption of Campi Flegrei in almost 4,000 years. It was preceded by a few decades of sporadic earthquakes swarms and noticeable uplift of the shoreline and was followed by 430 years of quiescence. Signs of renewed activity was first recognized in late 1969. Since then, the caldera center rose as much as 3 meters, and several hundred earthquakes were felt from 1983 to 1984 by people living in Campi Flegrei. These earthquakes extensively damaged buildings in Pozzuoli, located in the center of Campi Flegrei, and prompted the evacuation of 40,000 people. The uplift and the earthquakes stopped in December 1984, and no significant activity has occurred since. We cannot forecast whether the activity since 968 will culminate in another eruption or whether Campi Flegrei will remain quiet for several hundred more years. This article summarizes the historical recorded of activity in Campi Flegrei, which, with varying degrees of reliability, spans 2,000 years, and emphasizes that further scientific studies of this caldera will improve our understanding of the behavior of longquiescent volcanic system.

Earthquakes & Volcanoes (USGS)↗
USGS1992

Tracking the movement of Hawaiian volcanoes; Global Positioning System (GPS) measurement

Most, if not all, volcanic eruptions are preceded by surface movements near the volcano. These ground movements are the response of the shallow crust to the accumulation of the magma or the buildup of magma pressure within a subterranean reservoir beneath the volcano. As the magma reservoir expands, the summit and the flanks of the volcano rise and spread apart. Measurements made at many volcanoes show that slow ground movement may precede an eruption by as many as several years. Sudden increases in the rate of ground movement often precede an eruption by a few hours or days. At some well-studied volcanoes, surface movements of at least several centimeters take place out to distances of about 10 km from the summit of the volcano. Widespread deformation of this type is relatively easy to monitor, because the necessary survey stations can be placed at favorable sites some distance from the summit of the volcano. Examples of deformation of this type include Kilauea and Mauna Loa in Hawaii, Krafla in Iceland, Long Valley in California, Camp Flegrei in Italy, and Sakurajima in Japan. In contrast, surface movement at some other volcanoes, usually volcanoes with steep slopes, is restricted to places within about 1 km of their summits. Examples of this class of volcanoes include Mount St. Helens in Washington, Etna in Italy, and Tangkuban Parahu in Indonesia. Local movement on remote, rugged volcanoes of this type is difficult to observe using conventional methods of measuring ground movement, which generally require a clear line-of-sight between points of interest. However, a revolutionary new technique, called the Global Positional System (GPS), provides a very efficient, alternative method of making such measurements. GPS, which uses satellites and ground-based receivers to accurately record slight crustal movements, is rapidly becoming the method of choice to measure deformation at volcanoes.

Hawaii↗
USGS1993

Preventing volcanic catastrophe; the U.S. International Volcano Disaster Assistance Program

When the seismograph began to record the violent earth-shaking caused by yet another eruption of the Nevado del Ruiz volcano in Colombia, no one thought that a few hours later more than 23,000 people would be dead, killed by lahars (volcanic debris flows) in towns and villages several tens of kilometers away from the volcano. Before the fatal eruption the volcano was being monitored by scientists at a seismic station located 9 km from the summit, and information about the volcano's activity was being sent to Colombian emergency-response coordinators who were charged with alerting the public of the danger from the active volcano. Furthermore, area known to be in the pathways lahars had already been identified on maps and communities at risk had been told of their precarious locations. Unfortunately, a storm on November 13, 1985, obscured the glacier-clad summit of Nevado del Ruiz. On that night an explosive eruption tore through the summit and spewed approximately 20 million cubic meters of hot ash and rocks across the snow-covered glacier. These materials were transported across the snow pack by avalanches of hot volcanic debris (pyroclastic flows) and fast-moving, hot, turbulent clouds of gas and ash (pyroclastic surges). The hot pyroclastic flows and surges caused rapid melting of the snow and ice and created large volumes of water that swept down canyons leading away from the summit. As these floods of water descended the volcano, they picked up loose debris and soil from the canyon floors and walls, growing both in volume and density, to form hot lahars. In the river valleys farther down the volcano's flanks, the lahars were as much as 40 m thick and traveled at velocities as fast as 50 km/h. Two and a half hours after the start of the eruption one of the lahars reachered Armero, 74 km from the explosion crater. In a few short minutes most of the town was swept away or buried in a torrent of mud and boulders, and three quaters of the townspeople perished.

Nevado del Ruiz↗
USGS1988

Geological hazards programs and research in the U.S.A

Until recently, volcanic eruptions, earthquakes and major ground failures in populated regions have been viewed as natural disasters that were unpredictable and producing effects that were unavoidable. research over the past few decades has led to an increased understanding of the effects and causes of geological hazards and to a widening recognition that measures can be taken to reduce their impacts on people and structures. Thus, today, in the U.S.A and elsewhere, formal government programs have been established to study these hazrads, not only to explain and understand the phenomena themselves, but also to provide a basis for warning and mitigation strategies that will reduce losses and suffering.

Earthquakes & Volcanoes (USGS)↗
USGS1990

Inside active volcanoes; an exhibit on the move!

All of us are aware of the emphasis currently being placed in the United States on science education and public understanding of science. Most of this emphasis is directed toward mass audiences through book publications, school curricula, and television programs; sadly, most of it deals with non-earth science topics. In an effort to take advantage of this awakened consciousness and to highlight the earth sciences, the Smithsonian Institution and the U.S Geological Survey joined forces to prepare a traveling exhibit on volcanoes that is currently touring the country. This note will serve to bring you up to date on the progress of this exhibit as it reaches the mid-point of its tour.

Earthquakes & Volcanoes (USGS)↗
USGS1991

Volcanoes in outer space and inner space

AS a teenager, I spent many long, bone-chilling hours studying the Moon and the planets with a rickety, homemade telescope. After 30 years, I still recall the pain and pleasure of creeping illicitly out of the house in the small hours of the morning for the few moments of satisfaction when the boiling, bouncing image of Jupiter would come to rest momentarily in sharp focus, the Galilean satellites strung out like brilliant beads on either side of the flattened disc. For me, then, the most remarkable piece of volcanology in the last twenty years was the discovery of active volcanism on Io, one of those tiny points of light I grew to know so well, though I was never really sure which satellite was which. To be sure, flying in a helicopter over the wasteland surrounding Mount St. Helens shortly after the 1980 eruption left an indelible, visceral impression on me, as it must have done to a great many others. But the discovery of volcanism on Io was a stunning piece of pure science.

Earthquakes & Volcanoes (USGS)↗
USGS1990

Earthquakes in New England

Believe it or not, New England is earthquake country. No, it does not have the high frequency of earthquakes of California or Japan. nevertheless, New England has experienced its fair share of tremors. New England has a long history of earthquakes. Some of the first explorers were startled when they experienced strong shaking and rumbling of the earth below their feet. they soon learned from the Indians that this was not an uncommon occurrence in the New World. the Plymouth Pilgrims felt their first earthquake in 1638. that first shock rattled dishes, doors, and buildings. The shaking so frightened those working in the fields that they threw down their tools and ran panic-stricken through the countryside.

New England↗
USGS1991

Advances(?) in mitigating volcano hazards in Latin America

The 1980's were incredible years for volcanology. As a consequence of the Mount St. Helens and other eruptions, major advances in our understanding of volcanic processes and eruption dynamics were made. the decade also witnessed the greatest death toll caused by volcanism since 1902. Following Mount St. Helens, awareness of volcano hazards increased throughout the world; however, in Latin America, subsequent events showed that much was still to be learned.

Earthquakes & Volcanoes (USGS)↗
USGS1989

The Southern California Earthquake Survival Program

In July 1988, the Los Angeles County Board of Supervisors directed the Chief Administrative Office to develop an educational program aimed at improving earthquake preparedness among Los Angeles County residents. the board recognized that current earthquake education efforts were not only insufficient, but also often confusing and costly. The board unanimously approved the development of a program that would make earthquake preparedness a year-long effort by encouraging residents to take a different precaution each month.

California↗