how do geologists think about a watershed?
DESCRIPTION
How do geologists think about a watershed?. Rivers are just the surface. WATER & SEDIMENTS!. Geological river continuum:. From ridgetop raindrops & snowflakes To sediment washing down slopes To water & sediments in the “river” itself To water deep below the surface. - PowerPoint PPT PresentationTRANSCRIPT
How do geologists think about a watershed?
Rivers are just the surface
WATER &
SEDIMENTS!
Geological river continuum:
• From ridgetop raindrops & snowflakes
• To sediment washing down slopes
• To water & sediments in the “river” itself
• To water deep below the surface
Yakima watershed underpinnings
crystalline metamorphic rocks & granites--not very permeable
mostly sedimentary rocks--generally permeableexcept clays
basalts--permeable alongfaults
Adapted from Field Trip Guidebook to the Natural History of Kittitas County – J. Mabry
NW SE
before 200 million years
SUBDUCTION started ~200 million years ago
marine sediments get scraped off the down-going plate and plastered onto the continent
Volcanoes at the surface and granite cooling miles below the surface
Future Yakima Watershed(metamorphosed ocean sediments)
play animations
http://emvc.geol.ucsb.edu/1_DownloadPage/Download_Page.html#GlobalTectonics
Land gradually added to west coast since 200 million years ago
added land
Land soon to be scraped off onto the continent
terrestrial sedimentation and swamps 65-35 million years ago
Future Yakima Watershed(river sediments and swamp muck with a few basalt flows thrown in)
Columbia FloodBasalts
massive basalt flows 17-14 million yr
a single flow
Photo compliments of Nick Zenter
N-S compression gently folds
Yakima watershed
15 million years to present
Wells and Simpson (2001)
ridges
agriculturalvalleys
Ice Age - last 2 million
former glaciers’ paths
Yakima watershed underpinnings
crystalline metamorphic rocks & granites--not very permeable
mostly sedimentary rocks--generally permeableexcept clays
basalts--permeable alongfaults
Adapted from Field Trip Guidebook to the Natural History of Kittitas County – J. Mabry
NW SE
From Jones et al., 2006 (USGS)
From Fuhrer et al., 2004 (USGS)