Presentation

At the end of the last Ice Age an ice dam in northern Idaho created Glacial Lake Missoula stretching 3,000 square miles around Missoula, Montana. The dam burst and released flood waters across Washington, down the Columbia River into Oregon before reaching the Pacific Ocean. The Ice Age Floods forever changed the lives and landscape of the Pacific Northwest. The Ice Age Floods National Geologic Trail is a network of routes, sites, and interpretive centers that follow the pathways of the repeated Ice Age megafloods released from Glacial Lake Missoula between roughly 18,000 and 15,000 years ago. These floods reshaped the Pacific Northwest on a continental scale, carving features such as the Channeled Scablands, Grand Coulee, Dry Falls, Palouse Falls, and the Columbia River Gorge. It spans four states—Montana, Idaho, Washington, and Oregon—and links dozens of geologic landmarks that preserve evidence of these enormous floods. Presented by Don Chadbourne, geologist and board member of the Ice Age Floods Institute (IAFI), Cheney-Spokane Chapter No registration required. Call Librarian Ali Spahn with any questions at 208-683-2979.

At the end of the last Ice Age an ice dam in northern Idaho created Glacial Lake Missoula stretching 3,000 square miles around Missoula, Montana. The dam burst and released flood waters across Washington, down the Columbia River into Oregon before reaching the Pacific Ocean. The Ice Age Floods forever changed the lives and landscape of the Pacific Northwest. The Ice Age Floods National Geologic Trail is a network of routes, sites, and interpretive centers that follow the pathways of the repeated Ice Age megafloods released from Glacial Lake Missoula between roughly 18,000 and 15,000 years ago. These floods reshaped the Pacific Northwest on a continental scale, carving features such as the Channeled Scablands, Grand Coulee, Dry Falls, Palouse Falls, and the Columbia River Gorge. It spans four states—Montana, Idaho, Washington, and Oregon—and links dozens of geologic landmarks that preserve evidence of these enormous floods. Presented by Don Chadbourne, geologist and board member of the Ice Age Floods Institute (IAFI), Cheney-Spokane Chapter No registration required. Call Librarian Ani Matosian with any questions at 208-689-3976.

Geologist Michael Hamilton talks about the geology of the Spokane area which reveals an interesting part of the glacial flood story. When the glacial ice dam failed, the area immediately downstream received deposits of sediments and various landforms that provide clues of what happened when the dam burst. What we see in the flood deposits around Spokane also suggest insights on the sequence and size of the outburst floods. Presented by Michael Hamilton, geologist and board member of the Ice Age Floods Institute (IAFI), Cheney-Spokane Chapter No registration required. Call Librarian Grace Lippman with any questions at 208-773-1506.

 Giant Current Dunes or MegaRipple Marks – One of Bretz’ most important pieces of evidence for catastrophic flooding was the “giant current dunes.” These large-scale bedforms appeared as patterns of parallel ridges and swales on many aerial photographs in the flood channels in the scabland of Washington, but had escaped recognition from the ground because of their size.  Giant Current Dunes are visible west of Clark Fork near Castle Rock; however, the most prominent and visible Giant Current Dunes are located several miles east of Spirit Lake along Hwy 54 where the highway cuts through the dunes showing their undulating profile. The location of many of the telephone poles on the crest of these dunes accentuates these landforms. The dunes form transverse to the current direction, and form cusps that are convex upstream, with arms that point downstream. Furthermore, the size of the cusps appears to decrease in the direction of lower velocity. Internally, the dunes consist of gravel and pebble foresets. Giant current dunes exhibit an asymmetrical profile with the downstream (lee) slope steeper than the upstream slope. Crests range from 20 to 200m apart and heights range from 1 to 15m (Baker and Nummedal, 1978) and are among the largest measured throughout the Floods area. The Spirit Lake current dunes can also be easily recognized from the air by their characteristic pattern, accentuated by vegetation. This dune field is immediately in the path of the breakout from Lake Pend Oreille, and experienced some of the highest energy flows. Presented by Dr. Linda McCollum, president of the Ice Age Floods Institute (IAFI), Cheney-Spokane Chapter No registration required. Call Librarian Nicole Ferris with any questions at 208-623-5353.

How do geologists know when the ice age floods actually occurred in the Spokane area? One method is to date the large flood-rafted erratic boulders. We explore the ages of the floods and the methods used to determine their dates and present newly gathered dates from the Spokane region revealing when the floods happened.  Presented by Glenn Cruickshank, vice president of the Ice Age Floods Institute (IAFI), Cheney-Spokane Chapter, and Dr. Jim O'Connor, USGS No registration required. Call Librarian Kathleen Kennedy with any questions at 208-772-5612 x126.

How do geologists know when the ice age floods actually occurred in the Spokane area? One method is to date the large flood-rafted erratic boulders. We explore the ages of the floods and the methods used to determine their dates and present newly gathered dates from the Spokane region revealing when the floods happened.  Presented by Glenn Cruickshank, vice president of the Ice Age Floods Institute (IAFI), Cheney-Spokane Chapter No registration required. Call Librarian Tiffany Berg with any questions at 208-687-1029.