Lake Lewis Isles - Ice Age Floods Earthcache EarthCache
Lake Lewis Isles - Ice Age Floods Earthcache
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*****This is an Earthcache. Please note the special Earhcache requirements below to log this cache as a find. You need to email me the answers to the questions below. Happy Caching!
Upon reaching the cache coordinates imagine yourself at the edge of a lake that expands as far as your eye can see. If you can imagine this then add to your picture the occasional iceberg floating in the lake. Welcome to Lake Lewis!
Over 12,000 years ago, Ice Age floods repeatedly surrounded the Badger Mountain with glacial water. The source of this water was the breakup of ice dams at massive Lake Missoula, located near present-day northwestern Montana and Lake Pend Oreille in northern Idaho.
As the ice dams broke, floodwaters reached the Pasco Basin where Badger Mountain is located. These floodwaters reached elevations surpassing 1200' above sea level and created what was known as Lake Lewis. The "lake" was only temporary, however, gradually draining out of Wallula Gap.
The only other land one would have seen from this location when floodwaters forming Lake Lewis reached their maximum elevations, would only be the tops of Candy Mountain, Red Mountain and Rattlesnake Mountain located to the west. These mountain tops are often referred to at the Lake Lewis Isles.
Wallula Gap, located along the Horse Heaven Hills 22 miles southeast from this Earthcache, was narrow enough to cause hydraulic damming of flood waters behind Wallula Gap. This constriction caused the floodwaters to continually rise in Pasco Basin and surrounding the slopes of Badger Mountain. Lake Lewis also backflooded and filled the Yakima and Walla Walla Valleys.
Icebergs floating atop the lake became grounded during the drainage period, and some of these icebergs contained large boulders known as "erratics". These "erratics" were then left behind on mountain slopes and surrounding areas as the icebergs melted.
According to local geologist Bruce Bjonstad, an Ice Age Floods expert, boulders must meet two criteria to be called erratics: 1) they must be of a different type than the underlying bedrock, and 2) they must have been transported into position by ice, either from the glacier itself or rafted in on icebergs. Since the glacier never made it as far south as the Pasco Basin, erratics in the Pasco Basin and beyond are all of an ice-rafted origin. In the Pasco Basin about 75% of erratics are composed of granitic rocks with the other 25% mostly gneiss, quartzite and argillite.
Bruce points out the two granite boulders used as the markers were located on Badger Mountain by himself, George Last, Jim Langdon and others and are not in place. They were strategically located to take advantage of the high-water mark for the floods and nice views below. The other marker is located on the west side of Badger Mountain along the Skyline Trail.
To log this cache you must email me the answers to the following questions. Please do not post your answers in your log as these will be removed.
1. Using the information found on the marker at this location, calculate the difference in the maximum elevation of Lake Lewis during the floods and the current elevation of the Columbia River seen to the north. Assume the Columbia River currently has an elevation of approximately 341 feet above sea level. Please provide your answer in feet.
2. What object (use its technical name) is located at the following coordinates N46 14.182 W119 18.425 (near the trailhead below)? Hint the large object’s history is noted on the kiosk just to the west.
3. Lake Lewis was only temporarily gradually draining out at?
Pictures of the view during your trip up are encouraged. Just please don’t include the marker in question #1 or object mentioned in question #2.
Please park at the trailhead located at the base of the park and hike the Canyon Trail created and maintained by the Friends of Badger Mountain. To reach the summit you will have hiked 1.4 miles and had approximately 800 feet of elevation. The Earthcache is approximately halfway to the summit. While it is a climb it is family friendly and popular local trail so expect to see lots of other people during your visit. Please stay on the trail, enjoy the view, and get an Earthcache!
A special thank you to Bruce Bjornstad for his expertise.
Additional sources:
Bjornstad, B.N., 2006, On the Trail of the Ice Age Floods: A Geological Field Guide to the Mid-Columbia Basin, Keokee Co. Publishing, Inc., Sandpoint, Idaho, 308 p.
Ice Age Floods Institute - www.iafi.org
Additional Hints
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