Chalk Hills Glacial Lake Earthcache EarthCache
Chalk Hills Glacial Lake Earthcache
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Along Washington State Route 17 between Bridgeport and Coulee City
you run through an area called the Chalk Hills. White hills of the
badlands topography rising above the native grasses giving a
glimpse in to the distant past. Just south of this area is evidence
of the Great Ice Age Floods that scoured the landscape as recently
as 10,000 years ago. The Chalk Hills in contrast show a much more
recent erosion.
Several thousands of years ago during the Great Ice Age, the
Cordilleran Ice Sheet covered virtually all of southwestern Canada,
northern Washington, northern Idaho, and northwestern Montana. This
area where you are standing is part of the Foster Creek Watershed.
During the Great Ice Age there were several Glacial Lakes in this
area fed by the Okanogan Lobe of the Cordilleran Ice Sheet. Over
thousands of years glacial run off, heavy with sediment from the
scraping of the land as the glacier headed south, filled these
Glacial Lakes of Foster Creek. Think of the sediment rich lakes of
the Northern Rockies, such as Lake Louise. The Glacial Lake
sediments are evident in this valley area, only some of the area
has eroded to show the deep deposits from these ancient lakes.
Geologically speaking, recent erosion gives this area a badlands
appearance. Badlands is defined as: a barren area in which soft
rock strata are eroded into varied, fantastic forms. Because the
rocks are not uniform in character, differences in erosion result
in stair-step profiles. The joining and separating of the gullies
cause many isolated irregular spires, small flat-topped buttes, or
mesas, and produce a landscape of jagged, fluted, and seemingly
inaccessible hills.
To get credit for this Earthcache send an email to the owner with
the answers to the following:
1. Estimate the height of the sediment hills in this area that are
of a badlands type of topography.
2. Can you imagine the height of the lake above where you stand?
Can you estimate how many years that lake would need to have been
fed glacial runoff to get to the height of the sediment you
see?
3. There are some erosion spots near by, feel some of the white
deposits if you can. How does it feel? Fine, coarse, other?
You can post a picture, but please do not post the answers to your
questions in your log. Depending on the season that you visit the
area, watch out for wild life that could be hiding nearby.
Thank you.
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Be sure to visit the nearby cache GC1Q2EW
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