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