Thomas Winslow Sisson, PhD
I am a research geologist with the USGS Volcano Science Center. I have spent many years working on the geologic history and volcano hazards of Mount Rainier. My research interests include experimental petrology and volatile solubility of magmas.
Education and Certifications
Ph.D. Massachusetts Institute of Technology
M.S. UC Santa Barbara
B.S. Stanford University
Science and Products
Filter Total Items: 53
Petrogenesis of Mount Rainier andesite: Magma flux and geologic controls on the contrasting differentiation styles at stratovolcanoes of the southern Washington Cascades Petrogenesis of Mount Rainier andesite: Magma flux and geologic controls on the contrasting differentiation styles at stratovolcanoes of the southern Washington Cascades
Quaternary Mount Rainier (Washington, USA) of the Cascades magmatic arc consists of porphyritic calc-alkaline andesites and subordinate dacites, with common evidence for mingling and mixing with less evolved magmas encompassing andesites, basaltic andesites, and rarely, basalts. Basaltic andesites and amphibole andesites (spessartites) that erupted from vents at the north foot of the...
Authors
Thomas W. Sisson, V. J. M. Salters, P.B. Larson
Geologic map of southwestern Sequoia National Park, Tulare County, California Geologic map of southwestern Sequoia National Park, Tulare County, California
This map shows the geology of 675 km2 (260 mi2) on the west slope of the Sierra Nevada, California, mainly in Sequoia National Park and Sequoia National Forest. It was produced by the U.S. Geological Survey (USGS) at the request of the National Park Service to complete the geologic map coverage of Kings Canyon and Sequoia National Parks. The area includes the Mineral King 15’ topographic
Authors
Thomas W. Sisson, James G. Moore
Andesites of the 2009 eruption of Redoubt Volcano, Alaska Andesites of the 2009 eruption of Redoubt Volcano, Alaska
Crystal-rich andesites that erupted from Redoubt Volcano in 2009 range from 57.5 to 62.5 wt.% SiO2 and have phenocryst and phenocryst-melt relations consistent with staging in the upper crust. Early explosive products are low-silica andesites (LSA,
Authors
Michelle L. Coombs, Thomas W. Sisson, Heather A. Bleick, Sarah M. Henton, Christopher J. Nye, Allison Payne, Cheryl E. Cameron, Jessica F. Larsen, Kristi L. Wallace, Katharine F. Bull
Bedrock basins in the Sierra Nevada, Alta California Bedrock basins in the Sierra Nevada, Alta California
A 360-km-long belt of more than 1,400 meter-sized granitic bedrock basins occurs at 1,200 to 2,500 m elevation on the west flank of the Sierra Nevada. The circular, smooth basins are 0.7 to 1.7 min diameter and are commonly 50 to 1,000 liters in volume. They are man-made as shown by their restricted size and elevation range, uniform circular shape, distinct basin shapes in different...
Authors
James G. Moore, Mary A. Gorden, Thomas W. Sisson
Sixty thousand years of magmatic volatile history before the caldera-forming eruption of Mount Mazama, Crater Lake, Oregon Sixty thousand years of magmatic volatile history before the caldera-forming eruption of Mount Mazama, Crater Lake, Oregon
The well-documented eruptive history of Mount Mazama, Oregon, provides an excellent opportunity to use pre-eruptive volatile concentrations to study the growth of an explosive silicic magmatic system. Melt inclusions (MI) hosted in pyroxene and plagioclase crystals from eight dacitic–rhyodacitic eruptive deposits (71–7.7 ka) were analyzed to determine variations in volatile-element...
Authors
Heather M. Wright, Charles R. Bacon, Jorge A. Vazquez, Thomas W. Sisson
Segregating gas from melt: an experimental study of the Ostwald ripening of vapor bubbles in magmas Segregating gas from melt: an experimental study of the Ostwald ripening of vapor bubbles in magmas
Diffusive coarsening (Ostwald ripening) of H2O and H2O-CO2 bubbles in rhyolite and basaltic andesite melts was studied with elevated temperature–pressure experiments to investigate the rates and time spans over which vapor bubbles may enlarge and attain sufficient buoyancy to segregate in magmatic systems. Bubble growth and segregation are also considered in terms of classical steady...
Authors
Nicole C. Lautze, Thomas W. Sisson, Margaret T. Mangan, Timothy L. Grove
Science and Products
Filter Total Items: 53
Petrogenesis of Mount Rainier andesite: Magma flux and geologic controls on the contrasting differentiation styles at stratovolcanoes of the southern Washington Cascades Petrogenesis of Mount Rainier andesite: Magma flux and geologic controls on the contrasting differentiation styles at stratovolcanoes of the southern Washington Cascades
Quaternary Mount Rainier (Washington, USA) of the Cascades magmatic arc consists of porphyritic calc-alkaline andesites and subordinate dacites, with common evidence for mingling and mixing with less evolved magmas encompassing andesites, basaltic andesites, and rarely, basalts. Basaltic andesites and amphibole andesites (spessartites) that erupted from vents at the north foot of the...
Authors
Thomas W. Sisson, V. J. M. Salters, P.B. Larson
Geologic map of southwestern Sequoia National Park, Tulare County, California Geologic map of southwestern Sequoia National Park, Tulare County, California
This map shows the geology of 675 km2 (260 mi2) on the west slope of the Sierra Nevada, California, mainly in Sequoia National Park and Sequoia National Forest. It was produced by the U.S. Geological Survey (USGS) at the request of the National Park Service to complete the geologic map coverage of Kings Canyon and Sequoia National Parks. The area includes the Mineral King 15’ topographic
Authors
Thomas W. Sisson, James G. Moore
Andesites of the 2009 eruption of Redoubt Volcano, Alaska Andesites of the 2009 eruption of Redoubt Volcano, Alaska
Crystal-rich andesites that erupted from Redoubt Volcano in 2009 range from 57.5 to 62.5 wt.% SiO2 and have phenocryst and phenocryst-melt relations consistent with staging in the upper crust. Early explosive products are low-silica andesites (LSA,
Authors
Michelle L. Coombs, Thomas W. Sisson, Heather A. Bleick, Sarah M. Henton, Christopher J. Nye, Allison Payne, Cheryl E. Cameron, Jessica F. Larsen, Kristi L. Wallace, Katharine F. Bull
Bedrock basins in the Sierra Nevada, Alta California Bedrock basins in the Sierra Nevada, Alta California
A 360-km-long belt of more than 1,400 meter-sized granitic bedrock basins occurs at 1,200 to 2,500 m elevation on the west flank of the Sierra Nevada. The circular, smooth basins are 0.7 to 1.7 min diameter and are commonly 50 to 1,000 liters in volume. They are man-made as shown by their restricted size and elevation range, uniform circular shape, distinct basin shapes in different...
Authors
James G. Moore, Mary A. Gorden, Thomas W. Sisson
Sixty thousand years of magmatic volatile history before the caldera-forming eruption of Mount Mazama, Crater Lake, Oregon Sixty thousand years of magmatic volatile history before the caldera-forming eruption of Mount Mazama, Crater Lake, Oregon
The well-documented eruptive history of Mount Mazama, Oregon, provides an excellent opportunity to use pre-eruptive volatile concentrations to study the growth of an explosive silicic magmatic system. Melt inclusions (MI) hosted in pyroxene and plagioclase crystals from eight dacitic–rhyodacitic eruptive deposits (71–7.7 ka) were analyzed to determine variations in volatile-element...
Authors
Heather M. Wright, Charles R. Bacon, Jorge A. Vazquez, Thomas W. Sisson
Segregating gas from melt: an experimental study of the Ostwald ripening of vapor bubbles in magmas Segregating gas from melt: an experimental study of the Ostwald ripening of vapor bubbles in magmas
Diffusive coarsening (Ostwald ripening) of H2O and H2O-CO2 bubbles in rhyolite and basaltic andesite melts was studied with elevated temperature–pressure experiments to investigate the rates and time spans over which vapor bubbles may enlarge and attain sufficient buoyancy to segregate in magmatic systems. Bubble growth and segregation are also considered in terms of classical steady...
Authors
Nicole C. Lautze, Thomas W. Sisson, Margaret T. Mangan, Timothy L. Grove