The Columbia Plateau: A Land of Many Floods
Olivia Miller & Morgan Rosenberg
http://vulcan.wr.usgs.gov/Volcanoes/ColumbiaPlateau/Maps/map_columbia_plateau.html
•Miocene -Pliocene (17-6 Ma)
•174,000 km3 basalt
•300+ flows
•1.8 km thick
http://geomaps.wr.usgs.gov/parks/province/ColumbiaRelief.jpg
http://earthweb.ess.washington.edu/EPIC/Geologic/Missoula/thumbnails/46.EP_0187_DR_MF_46.jpg
http://www.cr.nps.gov/history/online_books/geology/publications/inf/72-2/sec5.htm
Dry Fallshttp://vulcan.wr.usgs.gov/Volcanoes/Washington/Maps/geologic_map_washington_state.html
Crust & Lithosphere Properties
• Columbia Arc (Blue Mtns.) divides the Columbia Plateau into regions of lower elevation to the north and higher elevation to the south
• Crustal thickness:• Within Plateau: ~ 25 km• Around arc/ borders: to 30 km
• P-wave velocity:• 8.1 km/s beneath plateau N of
arc • 7.8 – 8 km/s S of arc
•Heat flow high relative to avg. continental crust, but central portion of plateau has region of low heat flow relative to surrounding regions (< 1.5 heat flow units)
•Crustal Density using Gardner’s Relationship (ρ = .23 Vp .25)•N of arc: 2.94 g/cm3
•S of arc: 2.91 g/cm3
http://vulcan.wr.usgs.gov/Volcanoes/PacificNW/AGU-T106/CRBG_stratigraphic.html
Fossil soil layer
Erosional unconformities