James A Smith
James A Smith is a Geophysicist with the Earthquake Hazards Program.
Science and Products
Filter Total Items: 89
Geothermal segmentation of the Cascade Range in the USA Geothermal segmentation of the Cascade Range in the USA
Characteristics of the crustal thermal regime of the Quaternary Cascades vary systematically along the range. Spatially congruent changes in volcanic vent distribution, volcanic extrusion rate, hydrothermal discharge rate, and regional conductive heat flow define 5 geothermal segments. These segments are, from north to south: (1) the Washington Cascades north of Mount Rainier, (2) the...
Authors
Marianne Guffanti, L.J. Muffler, Robert H. Mariner, D. R. Sherrod, James G. Smith, D.D. Blackwell, C.S. Weaver
Mineralized and unmineralized calderas in Spain; Part II, evolution of the Rodalquilar caldera complex and associated gold-alunite deposits Mineralized and unmineralized calderas in Spain; Part II, evolution of the Rodalquilar caldera complex and associated gold-alunite deposits
The Rodalquilar caldera complex is located in the western part of the Cabo de Gata volcanic field in southeastern Spain and is the first documented example of epithermal gold-alunite mineralization within a caldera in Europe. The Rodalquilar caldera is an oval collapse structure having a maximum diameter of 8 km and formed at 11 Ma from eruption of the Cinto ash-flow tuff. The oval...
Authors
J. J. Rytuba, A. Arribas, C. G. Cunningham, E.H. McKee, M. H. Podwysocki, James G. Smith, W.C. Kelly, A. Arribas
Late Cenozoic volcanism, subduction, and extension in the Lassen region of California, southern Cascade Range Late Cenozoic volcanism, subduction, and extension in the Lassen region of California, southern Cascade Range
Some 537 volcanic vents younger than 7 Ma are identified and these are classified into five age intervals and five compositional categories based on SiO2 content. Maps of vents by age and composition illustrate regionally representative volcanic trends. By 2 Ma, the eastern limit of volcanism had contracted westward toward the late Quaternary arc. Late Quaternary volcanism is...
Authors
M. Guffanti, M.A. Clynne, James G. Smith, L.J.P. Muffler, T.D. Bullen
Age and progression of volcanism, Wrangell volcanic field, Alaska Age and progression of volcanism, Wrangell volcanic field, Alaska
The Wrangell volcanic field covers more than 10 000 km2 in southern Alaska and extends uninterrupted into northwest. Yukon Territory. Lavas in the field exhibit medium-K, calc-alkaline affinities, typical of continental volcanic arcs along convergent plate margins. Eleven major eruptive centers are recognized in the Alaskan part of the field. More than 90 K-Ar age determinations in the...
Authors
D.H. Richter, James G. Smith, M. A. Lanphere, G. B. Dalrymple, B.L. Reed, Nora B. Shew
Quaternary extrusion rates of the Cascade Range, northwestern United States and southern British Columbia Quaternary extrusion rates of the Cascade Range, northwestern United States and southern British Columbia
Quaternary (2–0 Ma) extrusion rates change significantly along the Cascade Range volcanic arc. The extrusion rate north of Mount Rainier is about 0.21 km3 km−1 m.y.−1; the rate in southern Washington and northern Oregon south to Mount Hood is about 1.6 km3 km−1 m.y.−1; in central Oregon the rate is 3–6 km3 km−1 m.y.−1; and in northern California, the rate is 3.2 km3 km−1 m.y.−1. Eruption...
Authors
D. R. Sherrod, James G. Smith
Rhyolitic calderas of the Yukon-Tanana Terrane, east central Alaska: volcanic remnants of a mid-Cretaceous magmatic arc Rhyolitic calderas of the Yukon-Tanana Terrane, east central Alaska: volcanic remnants of a mid-Cretaceous magmatic arc
Four large but poorly exposed rhyolitic calderas are present in the Yukon-Tanana terrane (YTT) in east central Alaska. At least two are mid-Cretaceous in age (~93 Ma). Similar volcanic rocks, the South Fork Volcanics, occur northeast of the Tintina fault in Yukon Territory. Evidence for the calderas consists of thick deposits of devitrified crystal- and lithic-rich densely welded tuff...
Authors
C. R. Bacon, H.L. Foster, James G. Smith
Non-USGS Publications**
**Disclaimer: The views expressed in Non-USGS publications are those of the author and do not represent the views of the USGS, Department of the Interior, or the U.S. Government.
Science and Products
Filter Total Items: 89
Geothermal segmentation of the Cascade Range in the USA Geothermal segmentation of the Cascade Range in the USA
Characteristics of the crustal thermal regime of the Quaternary Cascades vary systematically along the range. Spatially congruent changes in volcanic vent distribution, volcanic extrusion rate, hydrothermal discharge rate, and regional conductive heat flow define 5 geothermal segments. These segments are, from north to south: (1) the Washington Cascades north of Mount Rainier, (2) the...
Authors
Marianne Guffanti, L.J. Muffler, Robert H. Mariner, D. R. Sherrod, James G. Smith, D.D. Blackwell, C.S. Weaver
Mineralized and unmineralized calderas in Spain; Part II, evolution of the Rodalquilar caldera complex and associated gold-alunite deposits Mineralized and unmineralized calderas in Spain; Part II, evolution of the Rodalquilar caldera complex and associated gold-alunite deposits
The Rodalquilar caldera complex is located in the western part of the Cabo de Gata volcanic field in southeastern Spain and is the first documented example of epithermal gold-alunite mineralization within a caldera in Europe. The Rodalquilar caldera is an oval collapse structure having a maximum diameter of 8 km and formed at 11 Ma from eruption of the Cinto ash-flow tuff. The oval...
Authors
J. J. Rytuba, A. Arribas, C. G. Cunningham, E.H. McKee, M. H. Podwysocki, James G. Smith, W.C. Kelly, A. Arribas
Late Cenozoic volcanism, subduction, and extension in the Lassen region of California, southern Cascade Range Late Cenozoic volcanism, subduction, and extension in the Lassen region of California, southern Cascade Range
Some 537 volcanic vents younger than 7 Ma are identified and these are classified into five age intervals and five compositional categories based on SiO2 content. Maps of vents by age and composition illustrate regionally representative volcanic trends. By 2 Ma, the eastern limit of volcanism had contracted westward toward the late Quaternary arc. Late Quaternary volcanism is...
Authors
M. Guffanti, M.A. Clynne, James G. Smith, L.J.P. Muffler, T.D. Bullen
Age and progression of volcanism, Wrangell volcanic field, Alaska Age and progression of volcanism, Wrangell volcanic field, Alaska
The Wrangell volcanic field covers more than 10 000 km2 in southern Alaska and extends uninterrupted into northwest. Yukon Territory. Lavas in the field exhibit medium-K, calc-alkaline affinities, typical of continental volcanic arcs along convergent plate margins. Eleven major eruptive centers are recognized in the Alaskan part of the field. More than 90 K-Ar age determinations in the...
Authors
D.H. Richter, James G. Smith, M. A. Lanphere, G. B. Dalrymple, B.L. Reed, Nora B. Shew
Quaternary extrusion rates of the Cascade Range, northwestern United States and southern British Columbia Quaternary extrusion rates of the Cascade Range, northwestern United States and southern British Columbia
Quaternary (2–0 Ma) extrusion rates change significantly along the Cascade Range volcanic arc. The extrusion rate north of Mount Rainier is about 0.21 km3 km−1 m.y.−1; the rate in southern Washington and northern Oregon south to Mount Hood is about 1.6 km3 km−1 m.y.−1; in central Oregon the rate is 3–6 km3 km−1 m.y.−1; and in northern California, the rate is 3.2 km3 km−1 m.y.−1. Eruption...
Authors
D. R. Sherrod, James G. Smith
Rhyolitic calderas of the Yukon-Tanana Terrane, east central Alaska: volcanic remnants of a mid-Cretaceous magmatic arc Rhyolitic calderas of the Yukon-Tanana Terrane, east central Alaska: volcanic remnants of a mid-Cretaceous magmatic arc
Four large but poorly exposed rhyolitic calderas are present in the Yukon-Tanana terrane (YTT) in east central Alaska. At least two are mid-Cretaceous in age (~93 Ma). Similar volcanic rocks, the South Fork Volcanics, occur northeast of the Tintina fault in Yukon Territory. Evidence for the calderas consists of thick deposits of devitrified crystal- and lithic-rich densely welded tuff...
Authors
C. R. Bacon, H.L. Foster, James G. Smith
Non-USGS Publications**
**Disclaimer: The views expressed in Non-USGS publications are those of the author and do not represent the views of the USGS, Department of the Interior, or the U.S. Government.