Large rocks (till) at the base of a glacier that have been plucked from the terrain as the ice moved over it.
The Cordilleran Ice Sheet south into northern Washington, Idaho, and Montana MISSOULA & COLUMBIA LAKES
Ice Age 15,000 and 12,800 y.a. Near end of the Pleistocene Epoch
CORDILLERAN ICE SHEET LOBES 1Purcell Lobe blocked the Clark Fork River forming Lake Missoula Channeled Scabland 2Okanogan Lobe blocked the Columbia River (at Grand Coulee Dam) forming Glacial Lake Columbia (Grand Coulee, Banks Lake, Steamboat Rock, Dry Falls, & Moses Coulee) 3 The Puget Lobe scoured the Puget Sound
FINAL STAGES OF THE FLOOD Formed a new dam Causing the lake to refill Resulting in a new flood Average of every 55 years or so for 2,000 years! Each time Lake Missoula emptied the Purcell lobe continued its southerly progression
FINAL STAGES OF THE FLOOD Piles of rocks left behind near Eugene were brought by icebergs broken off the original ice dam formed by the Purcell lobe of the Cordilleran Ice Sheet
Many layers of glacial lake sediments are found situated on top of one another; each layer represents a separate filling of the lake Up to 40 times Flood Debris
FINAL STAGES OF THE FLOOD Not far from the present day site of Portland, the river makes two 90 degree turns. Ice and debris formed a temporary dam causing the floodwaters to spill into the Willamette Valley as far south as present day Eugene
Looking at the evidence Ancient shorelines on Mt. Jumbo Missoula, MT
The highest known shorelines are found at an elevation of 4,200 feet. Ancient shorelines on Mt. Jumbo Missoula, MT
13-30 feet these ripple marks would dwarf any ordinary ripple mark Camas Prairie ripple marks
Lake Columbia -- –across Spokane Cut deep canyons, or coulees in bedrock
Coulee south of Coulee City. Unlike the Grand Canyon, which was eroded by a river, the coulees of Washington were carved out by Ice Age floods. Okanogan Lobe
DRY FALLS by John Knapp http://www.bmi.net/knapp/whitman.html
Dry Falls Eastern Washington Photo compliments of the National Park Service Three & one-half miles wide, Dry Falls is five times the width of Niagara Falls Okanogan Lobe
OKANOGAN LOBE Soap Lake today is known as Dry Falls Skeleton of one of the greatest waterfalls Okanogan Lobe
OKANOGAN LOBE Dry Falls is 3.5 miles wide with a drop of over 400 ft.
OKANOGAN LOBE Two Major North South Grand Coulees * Larger Upper Coulee -a river over an 800 ft. waterfall [4 miles Wide & 20 miles Long] * Lower Coulee is [7 m long and about 1 mile wide] Eroding power took pieces of Basalt rock causing the falls to retreat 20 miles and self-destruct (where Grand Coulee Dam is today) Okanogan Lobe
Bibliography Alt, David. Glacial Lake Missoula and Its Humongous Floods. :Mountain Press Publishing Company, 2003. Alt, David and Donald W. Hyndman. Northwest Exposures: A Geologic Story of the Northwest. :Mountain Press Publishing Company, 1995.
Bibliography Durr, Gerald. Evidence of the Flood in Franklin County. July 17, 2003 Knapp, John. John Knapp’s Art Gallery. “Dry Falls, Washington”. July 5, 2003.