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The San Juan Mountains in southwestern Colorado have long been recognized as a site of exceptionally voluminous mid-Tertiary volcanism, including at least 24 major ignimbrite sheets (each 150-5,000 km3) and associated caldera structures active at 33-23 Ma. More recent volcanologic and petrologic studies in the San Juan region have focused mainly on several ignimbrite-caldera systems: the southeastern area (Platoro complex), western calderas (Uncompahgre-Silverton-Lake City), the central cluster (La Garita-Creede calderas). The northeast San Juan region that was far less studied until recently occupies a transition between earlier volcanism in central Colorado and the larger-volume younger ignimbrite-caldera foci...
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This geologic map database is a reproduction of U.S. Geological Survey Miscellaneous Investigations Map I–2362: “Geologic Map and Structure Sections of the Clear Lake Volcanics, Northern California” (Hearn, Donnelly-Nolan, and Goff, 1995). The database consists of a geologic map, three structural cross sections and a table of petrographic data for each map unit by mineral type, abundance, and size. The Clear Lake Volcanics are in the California Coast Ranges about 150 km north of San Francisco. This Quaternary volcanic field has erupted intermittently since 2.1 million years ago. This volcanic field is considered a high-threat volcanic system (Ewert and others, 2005). The adjacent Geysers geothermal field, the largest...
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This digital publication contains all the geologic map information used to publish U.S. Geological Survey Geologic Investigations Map Series SIM-3143 (Sherrod and others, 2021). This geologic map shows the distribution and stratigraphic relation of volcanic, intrusive, and sedimentary units emplaced in the past 8 million years across the eight principal islands of the Hawaiian archipelago, State of Hawaii, U.S.A. This geologic map database is accompanied by a report, which includes the formatted geologic map and explanatory pamphlet, available at https://doi.org/10.3133/sim3143​. The authors ask that users of the geologic map database cite both the report and the database: Report: Sherrod, D.R., Sinton, J.M.,...
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This geodatabase contains all the geologic map information for the Geologic Map of the San Juan caldera cluster, southwestern Colorado and is part of U.S. Geological Survey Geologic Investigations Map Series I-2799. The San Juan Mountains are the largest erosional remnant of a composite volcanic field that covered much of the southern Rocky Mountains in middle Tertiary time. The San Juan field consists mainly of intermediate-composition lavas and breccias, erupted about 35-30 Ma from scattered central volcanoes (Conejos Formation) and overlain by voluminous ash-flow sheets erupted from caldera sources. In the central San Juan Mountains, eruption of at least 8,800 km3 of dacitic-rhyolitic magma as nine major ash...
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This digital publication describes completely the hydrothermal, sedimentary, and volcanic deposits, as well as thermal features as a basis for understanding the hydrothermal processes and explosions in Pocket Basin, Yellowstone National Park, Wyoming at 1:2,400 scale.


    map background search result map search result map Database for the Geologic Map of the Bonanza Caldera Area, Northeastern San Juan Mountains, Colorado Database for the Geologic Map of Pocket Basin, Yellowstone National Park, Wyoming Database for the geologic map of the central San Juan caldera cluster, southwestern Colorado Geologic map database to accompany geologic map of the State of Hawaii Database for the Geologic Map and Structure Sections of the Clear Lake Volcanics, Northern California Database for the Geologic Map of Pocket Basin, Yellowstone National Park, Wyoming Database for the Geologic Map and Structure Sections of the Clear Lake Volcanics, Northern California Database for the geologic map of the central San Juan caldera cluster, southwestern Colorado Database for the Geologic Map of the Bonanza Caldera Area, Northeastern San Juan Mountains, Colorado Geologic map database to accompany geologic map of the State of Hawaii