Physics
Scientific paper
Dec 2002
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002agufm.v12b1426b&link_type=abstract
American Geophysical Union, Fall Meeting 2002, abstract #V12B-1426
Physics
8429 Lava Rheology And Morphology, 8450 Planetary Volcanism (5480)
Scientific paper
Young basaltic shields display morphologies unique from older shields that have undergone magmatic evolution. We have tested the validity of differentiating basaltic shields at different stages of magmatic evolution through analysis of their slope frequency distributions. Slopes are the irregular surface expressions of the processes that have formed the landscape. Therefore, unique slope distributions can be used to identify regions that have undergone unique formational processes. Young shields form a broad, gently sloping structure composed of long, overlapping lava flows. These flows are often erupted from a central source vent region. Throughout the magmatic evolution of a shield volcano, the erupted lavas gradually become more silicic. As the erupted lavas become more viscous, flow lengths decrease causing slopes to increase near the summit. Late stage shield volcanism is typified by eruption of lavas from numerous vents producing steep sided cones that are superimposed on the shield's flanks. As a shield volcano ages, its morphometry evolves due to the changing lava flow emplacement conditions. Slope analyses should detect the differing emplacement conditions that exist between young and old shields as unique slope frequency distributions. We have conducted slope frequency studies on the USGS, 10 m Digital Elevation Models (DEMs) for the Hawaiian shields Mauna Kea and Mauna Loa. Slopes were calculated from a complete Hawaiian DEM, mosaiced in ArcView GIS 3.2 by ESRI (Environmental Systems Research Institute, Inc.). A slope frequency plot, or histogram, is produced for each shield. Mauna Loa displays a gaussian distribution of slopes centered at 15 degrees while the older shield, Mauna Kea, displays a gaussian distribution that is skewed towards higher slopes centered at 21 degrees. The unique slope signatures of the two volcanoes highlight the unique flow emplacement conditions for shields at different stages of magmatic evolution. Slope frequency distribution analyses could also be capable of identifying the unique flow field emplacement processes that form Flood- and Plains-style basaltic provinces. If so, these studies can be used to further characterize basaltic provinces on any planetary surface for which reliable topographic data exists.
Bleacher Jacob E.
Greeley Ronald
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