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4 recordsLinked to original sources
USGS2007

Mid-Holocene change in types of degassing volcanoes, using indium in Antarctic ice as a tracer of volcanic source type

Proportions of trace metals in Antarctic ice samples indicate that the type of volcanoes that dominated atmospheric emissions changed at about the middle of the Holocene from relatively mafic, deep source volcanoes to more silicic, shallower-source volcanoes. We base this inference on the strong contrast in the abundances of the trace metal indium (In), relative to other trace metals present in ice, deposited at different times in the past, and on contrasting In abundances in modern emissions of volcanoes of different types. Indium is more abundant in the emissions of deep-source mafic volcanoes than in more felsic, shallower-source volcanoes. Earlier workers have shown, on the basis of petrologic and some meteoritic evidence, that In may be partitioned to the interiors (stony mantles) of differentiated planets, or enriched in the liquids of partly crystallized mafic melts.

Geophysical Research Letters↗
USGS2010

Coastal-change and glaciological map of the Ross Island area, Antarctica

Reduction in the area and volume of Earth?s two polar ice sheets is intricately linked to changes in global climate and to the resulting rise in sea level. Measurement of changes in area and mass balance of the Antarctic ice sheet was given a very high priority in recommendations by the Polar Research Board of the National Research Council. On the basis of these recommendations, the U.S. Geological Survey used its archive of satellite images to document changes in the cryospheric coastline of Antarctica and analyze the glaciological features of the coastal regions. The Ross Island area map is bounded by long 141? E. and 175? E. and by lat 76? S. and 81? S. The map covers the part of southern Victoria Land that includes the northwestern Ross Ice Shelf, the McMurdo Ice Shelf, part of the polar plateau and Transantarctic Mountains, the McMurdo Dry Valleys, northernmost Shackleton Coast, Hillary Coast, the southern part of Scott Coast, and Ross Island. Little noticeable change has occurred in the ice fronts on the map, so the focus is on glaciological features. In the western part of the map area, the polar plateau of East Antarctica, once thought to be a featureless region, has subtle wavelike surface forms (megadunes) and flow traces of glaciers that originate far inland and extend to the coast or into the Ross Ice Shelf. There are numerous outlet glaciers. Glaciers drain into the McMurdo Dry Valleys, through the Transantarctic Mountains into the Ross Sea, or into the Ross Ice Shelf. Byrd Glacier is the largest. West of the Transantarctic Mountains are areas of blue ice, readily identifiable on Landsat images, that have been determined to be prime areas for finding meteorites. Three subglacial lakes have been identified in the map area. Because McMurdo Station, the main U.S. scientific research station in Antarctica, is located on Ross Island in the map area, many of these and other features in the area have been studied extensively. The paper version of this map is available for purchase from the USGS Store.

IMAP↗