Publications

The Cascade Range of the Pacific Northwest has more than a dozen potentially active volcanoes. Cascade volcanoes tend to erupt explosively, and on average two eruptions occur per century—the most recent were at Mount St. Helens, Washington (1980–86 and 2004–8), and Lassen Peak, California (1914–17). To help protect the Pacific Northwest’s rapidly expanding population, USGS scientists at the Cascad

The distinctive morphology and relatively short geological range (3.25 to 2.5 Ma) of Thalassiosira vulniflca (Gombos) Fenner make it especially useful for Pliocene biostratigraphic studies in the Antarctic region. Thalassiosira fasciculata Harwood et Maruyama has a geological range (4.5 to 0.75 Ma) that overlaps that of T. vulnifica and it resembles this taxon in possessing prominent fultoportulae

Studies of Mount Shasta indicate that eruptive activity has occurred, on the average, once every 800 years. Debris flows and deposits of non- eruptive origin, in addition to those associated with eruptive activity (lava flows, pyroclastic flows, and ash fall), inundate the fans and channels and can endanger people or property on the flanks of the mountain. This study evaluates the source and chara

The seismic wavefield near an active volcanic vent consists of superimposed signals in a wide range of frequency bands from sources inside and outside the volcano. To characterize the broadband wavefield near Puu Oo, we deployed a profile of three three-component broadband sensors in a 200 m long line about 1.5 km WSW of the active vent. During this period, Puu Oo maintained a constant, but very l

No abstract available.

Earthquakes occur in clusters. After one earthquake happens, we usually see others at nearby (or identical) locations. To talk about this phenomenon, seismologists coined three terms foreshock , mainshock , and aftershock. In any cluster of earthquakes, the one with the largest magnitude is called the mainshock; earthquakes that occur before the mainshock are called foreshocks while those that occ

A proposed high-altitude survey of the U.S. with an ER-2 to collect radar data offers an exciting and cost-effective opportunity to collect magnetic anomaly data. At this workshop, a group of magnetic specialists addressed this opportunity by discussing the need for high-altitude magnetic data and by formulating a preliminary operational plan to acquire such data. The high-altitude aeromagnetic su

A program of temperature studies of the eruptive products of Mount St. Helens was established May 20, 1980, 2 days after the catastrophic eruption of May 18. Temperature-depth profiles were measured by thermocouple to determine the emplacement temperatures of deposits of the debris avalanche and blast of May 18 and of deposits of the pyroclastic flows of May 18, May 25, June 12, July 22, August 7,

No abstract available.

No abstract available.

During 1993, the Alaska Volcano Observatory (AVO) responded to episodes of eruptive activity or false alarms at nine volcanic centers in the state of Alaska. Additionally, as part of a formal role in KVERT (the Kamchatkan Volcano Eruption Response Team), AVO staff also responded to eruptions on the Kamchatka Peninsula, details of which are summarized in Miller and Kurianov (1993). In 1993, AVO ma

The U.S. Geological Survey's Cascades Volcano Observatory (CVO) has been testing low-cost, low-power Global Positioning System (GPS) receivers for use in the monitoring of restless volcanoes. Field tests of two single-frequency (L1 only) receivers, the Ashtech SCA-12S and the Leica SR261 show that these units can measure positions precisely enough to meet our monitoring needs. For line lengths up