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
Paleomagnetism of the Harrat Rahat volcanic field, Kingdom of Saudi Arabia—Geologic unit correlations and geomagnetic cryptochron identifications Paleomagnetism of the Harrat Rahat volcanic field, Kingdom of Saudi Arabia—Geologic unit correlations and geomagnetic cryptochron identifications
Paleomagnetic rock samples were collected from 173 drill sites in the Quaternary alkali basaltic volcanic field of northern Harrat Rahat, Kingdom of Saudi Arabia. Laboratory measurements on these samples established that lava flows and vent complexes—identified and mapped from field characteristics, rock types, and compositions as products of single or temporally close eruptions...
Authors
Duane Champion, Drew Downs, Mark Stelten, Joel E. Robinson, Thomas Sisson, Jamal Shawali, Khalid Hassan, Hani Zahran
Isotopic and geochemical evidence for the source of volcanism at Harrat Rahat, Kingdom of Saudi Arabia Isotopic and geochemical evidence for the source of volcanism at Harrat Rahat, Kingdom of Saudi Arabia
Pleistocene and Holocene basalts, hawaiites, mugearites, benmoreites, and trachytes from the northern part of the Harrat Rahat volcanic field, Kingdom of Saudi Arabia, were analyzed for Sr, Nd, Hf, and Pb isotopic compositions. Evolved trachytes with Mg number 0.1, consisting chiefly of alkali basalts but encompassing hawaiites, mugearites, and benmoreites, show a limited range in Hf, Nd...
Authors
Vincent Salters, Afi Sachi-Kocher, Drew Downs, Mark Stelten, Thomas Sisson
Explosive trachyte eruptions from the Al Efairia volcanic center in northern Harrat Rahat, Kingdom of Saudi Arabia Explosive trachyte eruptions from the Al Efairia volcanic center in northern Harrat Rahat, Kingdom of Saudi Arabia
Harrat Rahat is an alkali basalt, continental, intraplate volcanic field located within the central-western part of the Kingdom of Saudi Arabia. The northern quarter of Harrat Rahat contains evolved volcanic products that achieve trachyte compositions (>60 weight percent SiO2). Within the Al Efairia volcanic center, pyroclastic-flow and -surge deposits that reflect explosive trachyte...
Authors
Drew Downs, Mark Stelten, Hannah R. Dietterich, Duane Champion, Gail A. Mahood, Thomas Sisson, Andrew Calvert, Jamal Shawali
Mantle origin and crustal differentiation of basalts and hawaiites of northern Harrat Rahat, Kingdom of Saudi Arabia Mantle origin and crustal differentiation of basalts and hawaiites of northern Harrat Rahat, Kingdom of Saudi Arabia
Quaternary volcanic rocks of northern Harrat Rahat, Kingdom of Saudi Arabia, are chiefly alkali basalts with subordinate transitional basalts, hawaiites, mugearites, benmoreites, and trachytes. Geochemical and isotopic results indicate that crystallization-differentiation, mixing, and cumulate reassimilation within the magmatic system produced most of its compositional diversity, with...
Authors
Thomas Sisson, Drew Downs, Andrew Calvert, Hannah R. Dietterich, Gail A. Mahood, Vincent Salters, Mark Stelten, Jamal Shawali
Garnet stability in arc basalt, andesite, and dacite—An experimental study Garnet stability in arc basalt, andesite, and dacite—An experimental study
Garnet’s stability in arc magmas and its influences on their differentiation were explored experimentally in a typical basalt, andesite, and dacite at conditions of 0.9–1.67 GPa, 800–1300 °C, with 2–9 wt.% added H2O, and with oxygen fugacity buffered near Re + O2 = ReO2 (~ Ni-NiO + 1.7 log10 bars). Garnet did not grow at 0.9 GPa in any of the compositions, even with garnet seeds added to
Authors
Dawnika Blatter, Thomas Sisson, W. Hankins
Geologic field-trip guide to volcanism and its interaction with snow and ice at Mount Rainier, Washington Geologic field-trip guide to volcanism and its interaction with snow and ice at Mount Rainier, Washington
Mount Rainier is the Pacific Northwest’s iconic volcano. At 4,393 meters and situated in the south-central Cascade Range of Washington State, it towers over cities of the Puget Lowland. As the highest summit in the Cascade Range, Mount Rainier hosts 26 glaciers and numerous permanent snow fields covering 87 square kilometers and having a snow and ice volume of about 3.8 cubic kilometers...
Authors
James Vallance, Thomas Sisson
Science and Products
Filter Total Items: 53
Paleomagnetism of the Harrat Rahat volcanic field, Kingdom of Saudi Arabia—Geologic unit correlations and geomagnetic cryptochron identifications Paleomagnetism of the Harrat Rahat volcanic field, Kingdom of Saudi Arabia—Geologic unit correlations and geomagnetic cryptochron identifications
Paleomagnetic rock samples were collected from 173 drill sites in the Quaternary alkali basaltic volcanic field of northern Harrat Rahat, Kingdom of Saudi Arabia. Laboratory measurements on these samples established that lava flows and vent complexes—identified and mapped from field characteristics, rock types, and compositions as products of single or temporally close eruptions...
Authors
Duane Champion, Drew Downs, Mark Stelten, Joel E. Robinson, Thomas Sisson, Jamal Shawali, Khalid Hassan, Hani Zahran
Isotopic and geochemical evidence for the source of volcanism at Harrat Rahat, Kingdom of Saudi Arabia Isotopic and geochemical evidence for the source of volcanism at Harrat Rahat, Kingdom of Saudi Arabia
Pleistocene and Holocene basalts, hawaiites, mugearites, benmoreites, and trachytes from the northern part of the Harrat Rahat volcanic field, Kingdom of Saudi Arabia, were analyzed for Sr, Nd, Hf, and Pb isotopic compositions. Evolved trachytes with Mg number 0.1, consisting chiefly of alkali basalts but encompassing hawaiites, mugearites, and benmoreites, show a limited range in Hf, Nd...
Authors
Vincent Salters, Afi Sachi-Kocher, Drew Downs, Mark Stelten, Thomas Sisson
Explosive trachyte eruptions from the Al Efairia volcanic center in northern Harrat Rahat, Kingdom of Saudi Arabia Explosive trachyte eruptions from the Al Efairia volcanic center in northern Harrat Rahat, Kingdom of Saudi Arabia
Harrat Rahat is an alkali basalt, continental, intraplate volcanic field located within the central-western part of the Kingdom of Saudi Arabia. The northern quarter of Harrat Rahat contains evolved volcanic products that achieve trachyte compositions (>60 weight percent SiO2). Within the Al Efairia volcanic center, pyroclastic-flow and -surge deposits that reflect explosive trachyte...
Authors
Drew Downs, Mark Stelten, Hannah R. Dietterich, Duane Champion, Gail A. Mahood, Thomas Sisson, Andrew Calvert, Jamal Shawali
Mantle origin and crustal differentiation of basalts and hawaiites of northern Harrat Rahat, Kingdom of Saudi Arabia Mantle origin and crustal differentiation of basalts and hawaiites of northern Harrat Rahat, Kingdom of Saudi Arabia
Quaternary volcanic rocks of northern Harrat Rahat, Kingdom of Saudi Arabia, are chiefly alkali basalts with subordinate transitional basalts, hawaiites, mugearites, benmoreites, and trachytes. Geochemical and isotopic results indicate that crystallization-differentiation, mixing, and cumulate reassimilation within the magmatic system produced most of its compositional diversity, with...
Authors
Thomas Sisson, Drew Downs, Andrew Calvert, Hannah R. Dietterich, Gail A. Mahood, Vincent Salters, Mark Stelten, Jamal Shawali
Garnet stability in arc basalt, andesite, and dacite—An experimental study Garnet stability in arc basalt, andesite, and dacite—An experimental study
Garnet’s stability in arc magmas and its influences on their differentiation were explored experimentally in a typical basalt, andesite, and dacite at conditions of 0.9–1.67 GPa, 800–1300 °C, with 2–9 wt.% added H2O, and with oxygen fugacity buffered near Re + O2 = ReO2 (~ Ni-NiO + 1.7 log10 bars). Garnet did not grow at 0.9 GPa in any of the compositions, even with garnet seeds added to
Authors
Dawnika Blatter, Thomas Sisson, W. Hankins
Geologic field-trip guide to volcanism and its interaction with snow and ice at Mount Rainier, Washington Geologic field-trip guide to volcanism and its interaction with snow and ice at Mount Rainier, Washington
Mount Rainier is the Pacific Northwest’s iconic volcano. At 4,393 meters and situated in the south-central Cascade Range of Washington State, it towers over cities of the Puget Lowland. As the highest summit in the Cascade Range, Mount Rainier hosts 26 glaciers and numerous permanent snow fields covering 87 square kilometers and having a snow and ice volume of about 3.8 cubic kilometers...
Authors
James Vallance, Thomas Sisson