Glacial Lake Missoula: Hellgate Canyon EarthCache
Glacial Lake Missoula: Hellgate Canyon
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This Earthcache is located about 1/2 mile from the free parking
area near the Pedestrian bridge and Dog Park, along the Kim
Williams Trail next to the University of Montana campus.
This trail is part of a trail system that runs almost the entire
length of Missoula along the river and continues past the cache
point for another 2-3 miles to an old railroad bridge.
About 13,000 years ago, this entire valley was filled with water
950 ft deep. It was called Glacial Lake Missoula. And then the ice
dam located in Idaho broke and the water flooded out through
Washington to the Pacific Ocean. This was the last time the valley
was filled but not the only time.
Our valley filled up with water between 36 and 40 times, creating
shorelines on the mountains that can still be seen today. They are
faint, but with the right light or light snow they can be seen.
Counting them is difficult and can vary greatly given local
conditions like angle of viewing and amount of light.
The area you are in is called Hellgate Canyon. It was sculpted by
the flowing floodwater. The south canyon wall, Mount Sentinel, was
scrubbed bare of soil. It has since been covered by the loose talus
you see on the slope near the cache coordinates. The north canyon
wall, Mount Jumbo, escaped the fast currents that stripped the
south side bare, and therefore retained its soil. This is why you
can still see the shorelines there.
Location: Western Montana and Idaho Panhandle
Lake Type : Glacial
Lake area : 2900 sq miles at highest shoreline
Water contained: 530 cubic miles
Surface elevation: 4250 ft at maximum fill level
Depth: 950 ft (Missoula) - 2000 ft (at ice dam)
Information for this cache was taken from:
"Glacial Lake Missoula and Its Humongous Floods" by David Alt
2001, Mountain Press Publishing Company
Side-note: David Alt is a geology professor at the University of
Montana and has taught two generations of our family.
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To claim this cache you must complete the following:
1) Estimate the distance across the valley floor from where you are
to the other side of the valley. (Towards Mount Jumbo on the other
side of the river.) Email your answer to the cache owner. Please DO
NOT post your answer with your log entry.
OPTIONAL:
2) Have your picture taken holding your GPS (if possible, we know
some GPSr are also cameras/phones) with the sign near the cache
coordinates. Post your picture with your log entry for this
cache.
FUN BONUS QUESTION:
1) At the cache coordinates, count the number of shorelines you see
on Mount Jumbo. Please post your answer with your log entry.
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Additional Hints
(Decrypt)
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Treasures
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