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Floods of Change Imagine the greatest floods on earth crashing across and sculpting the lands of the northwestern United States. This incredible true story is recorded in rock and sediment. You can explore the geologic clues and landscapes made by the Ice Age Floods at sites along the Ice Age Floods National Geologic Trail. At the end of the last Ice Age, about 18,000 to 15,000 years ago, an ice dam blocked the Clark Fork River in what is now northern Idaho. Water rose 2,000 feet (610 m) behind the dam and stretched eastward 200 miles (322 km), creating Glacial Lake Missoula. Eventually, the ice dam weakened, burst, and released as much as 500 cubic miles (2,084 km3) of waterabout the volume of Lake Ontario and Lake Erie combinedin just two days. A wall of water hundreds of feet high thundered downstream at 65 miles per hour (105 km/hour) with 10 times more water than all the world's rivers today. This massive flood of water, ice, and debris shook the ground as it raced westward over 16,000 square miles (41,440 km2) in present-day Montana, Idaho, Washington, and Oregon. Over thousands of years, an ice dam repeatedly formed and burst, causing dozens of floods. Today, widespread reminders of these Ice Age Floods dot the landscape; gigantic basalt coulees, enormous dry falls, large boulders moved hundreds of miles, high water lines, and huge current ripples. These outstanding examples of cataclysmic flood geology, exceptional scenery, and places for scientific research are all part of the Ice Age Floods National Geologic Trail. Solving the Mystery The story of the Ice Age Floods took nearly 50 years to piece together. During the 1920s-40s geologists debated the origin of eastern Washington's Channeled Scabland where eroded volcanic basalt surrounds braided channels and coulees. Most geologists believed that the Channeled Scabland was made by slow erosion by glaciers and streams. Geologic evidence that didn't fit with this idea led geologist J Harlen Bretz to hypothesize that the Channeled Scabland was formed by cataclysmic floods. Initially ridiculed, Bretz's hypothesis was validated when new technologies like satellite photography provided supporting evidence. By the 1970s it was universally accepted that the scoured landscape of the northwestern United States was the result of the Ice Age Floods. J Harlen Bretz, 1882-1981 A high school teacher turned geology professor, J Harlen Bretz was fascinated with the glacial geology of the Puget Sound. He became an expert on the features of stream and glacial erosion and began field research in the Channeled Scabland of eastern Washington in 1922. Challenging common beliefs, Bretz believed that the Channeled Scabland was formed not by ordinary stream erosion but by cataclysmic floods. What eluded him, though, was the source of the floods. Joseph Pardee, 1871-1960 Joseph Pardee, a geologist with the US Geological Survey, proposed a source for Bretz's catastrophic floods. As he studied the Channeled Scabland and the intermountain basins of Montana in 1910, he found high water marks near Missoula, Montanaevidence of a large glacial lake. Later, in the Camas Prairie of northwestern Montana, he discovered giant ripple marks of sediment made by powerful currents flowing over the bottom of ancient Glacial Lake Missoula. Like Bretz, Pardee's discoveries played a key role in understanding the story of the Ice Age Floods. The work of these and present-day scientists show us that the gradual processes shaping our Earth can be punctuated by sudden, cataclysmic events, and that such events are possible in our lifetimes!
Lasting Impressions As the Ice Age Floods swept across the landscape from Montana to the Pacific Ocean, they eroded massive amounts of rock and debris from the land and deposited them farther down the flood route. Along the national geologic trail, deeply eroded coulees, scoured water gaps, remnant waterfalls, and basalt cliffs lead to gravel bars, giant ripple marks, and large boulders. These clues from the past guide your passage through geologic space and time. As you learn about 13 flood features here, find them on the map (see below) marked by numbered stars. 1. Lake Missoula Strandlines 2. Camas Prairie Ripples 3. Eddy Narrows 4. Glacial Dam at Green Monarch Ridge 5. Missoula Floods Outburst Plain 6. Sunset Prairie Antidune Field 7. Dry Falls at Grand Coulee 8. Drumheller Channels (NNL) 9. Palouse Falls 10. Wallula Gap (NNL) 11. Columbia River Gorge 12. Lower Columbia 13. Astoria Fan Plan Your Visit
Follow the path of the Ice Age Floods through the fascinating landscape of some of the largest known floods in the geologic record. The Ice Age Floods National Geologic Trail is a driving route that leads you about 3,380 miles (5,439 km) through Montana, Idaho, Washington, and Oregon. The National Park Service manages the trail in collaboration with other federal agencies, state parks, private land owners, and the Ice Age Floods Institute. Operating Hours Because the Ice Age Floods National Geologic Trail includes dozens of parks, museums, and sites across four states, operating hours and seasons vary. We recommend calling sites to check their hours before visiting. Unstaffed sites are usually open from dawn to dusk. Find a list of parks and museums to visit at www.nps.gov/iafl. Safety Preparation is key to a successful visit. Please know your route. Not all routes are appropriate for large trailers or RVs. Some sites are remote, so have sufficient gas, drinking water, food, sun protection, layers of clothing, and other essential supplies as needed. Fees and Permits Fees and permits vary by location. Most federal public lands such as national parks, national forests, and lands managed by the Bureau of Reclamation honor the America the Beautiful National Parks and Federal Recreational Lands Pass. State parks throughout Montana, Idaho, Washington, and Oregon require entrance fees and/or parking passes. Information on state park passes can be found at: StateParks.MT.gov Parking Some sites may have very limited parking. Leave No Trace The Ice Age Floods National Geology Trail highlights a significant geologic story. As you visit, help protect this national treasure by following Leave No Trace principles. Find more information at LNT.org. Learn More Some sites have interpretive signs. Explore the trail's website at www.nps.gov/iafl for additional information. The Ice Age Floods Institute is an educational nonprofit organization dedicated to advocacy of the floods story. The institute was instrumental in the 2009 passage of federal legislation authorizing the National Park Service to establish the Ice Age Floods National Geologic Trail. Learn more about these magnificent floods on the institute's website at www.iafi.org. National Natural Landmarks (NNL) The National Park Service has designated over 600 sites as National Natural Landmarks in recognition of their outstanding biological or geological features. They illustrate the diversity of the country's landscape and tell the story of our natural heritage. Found in both rural and urban settings, some have public access while others do not. National Natural Landmarks highlight the location and significance of America's natural features so that we may safeguard these sites today and in the future. Eight sites along the Ice Age Floods National Geologic Trail are distinguished as National Natural Landmarks. They nclude: Glacial Lake Missoula in Montana; Drumheller Channels, Ginkgo Petrified Forest, Grand Coulee, The Great Gravel Bar of Moses Coulee, and Wallula Gap in Washington; and Crown Point and the Willamette Floodplain in Oregon. Visit www.nps.gov/subjects/nnlandm for more information. Source: NPS Brochure (2021)
Brochures ◆ Site Bulletins ◆ Trading Cards Documents Flood Basalts and Glacier Floods: Roadside Geology of Parts of Walla Walla, Franklin, and Columbia Counties, Washington (HTML edition) State of Washington Department of Natural Resources Division of Geology and Earth Resources Information Circular 90 (Robert J. Carson and Kevin R. Pogue, January 1996) Foundation Document, Ice Age Floods National Geologic Trail, Montana/Idaho/Washington/Oregon (Draft, September 2011) Foundation Document Overview, Ice Age Floods National Geologic Trail, Montana/Idaho/Washington/Oregon (July 2014) Geology of Portland, Oregon, and adjacent areas U.S. Geological Survey Bulletin 1119 (Donald E. Trimble, 1963) Geology of the Grand Coulee (Joseph G. McMacken, 1936) Grand Coulee of Washington: The Grand Coulee in Picture and Story and Columbia Basin Irrigation Project (Joseph G. McMacken, 1942) Guidebook of the Western United States: Part A: The Northern Pacific Route with a Side Trip to Yellowstone Park U.S. Geological Survey Bulletin 611 (Marius R. Campbell and others, 1916) Guidebook to Quaternary Geology of the Columbia, Wenatchee, Pehastin, and Upper Yakima Valleys, West-Central Washington U.S. Geological Survey Open-File Report 77-753 (Richard B. Waitt, Jr., 1977) Late Pleistocene Flood Deposits in the Portland Area (James Stauffer, extract from Geological News Letter, Vol. 22 No. 3, March 1956, Geological Society of the Oregon Country) Late Pleistocene Sediments and Floods in the Willamette Valley (Ira S. Allison, extract from The Ore Bin, Vol. 40 No. 12, December 1978) Long-range Interpretive Plan, Ice Age Floods National Geologic Trail (Gookrick Interpretive Group, June 2016) Megaflood Adventure Junior Ranger Activity Book, Ice Age Flood National Geologic Trail (July 2019; for reference purposes only) Physiography and Glacial Geology of Western Montana and Adjacent Areas U.S. Geological Survey Professional Paper 231 (W.C. Alden, 1953) Reference List for the Ice Age Floods (2019) Study of Alternatives and Environmental Assessment: Following the Pathways of the Glacial Lake Missoula Floods (Jones & Jones, February 2001) Tens of Successive, Colossal Missoula Floods at North and East Margins of Channeled Scabland U.S. Geological Survey Open-File Report 83-671 (Richard B. Waitt, Jr., August 1983) The Channeled Scabland: A Guide to the Geomorphology of the Columbia Basin, Washington (Victor B. Baker and Dag Nummedal, eds., 1978) The Channeled Scabland of Eastern Washington (J. Harlen Bretz, extract from The Geographical Review, Vol. XVIII No. 3, July 1928) The Channeled Scablands of Eastern Washington: The Geologic Story of the Spokane Flood (HTML edition) USGS Information Circular 72-2 (Paul L. Weis and William L. Newman, 1976) The Channeled Scablands of Eastern Washington: The Geologic Story of the Spokane Flood (Paul L. Weis and William L. Newman, 2nd ed., 1989) The Channeled Scablands of the Columbia Plateau (J. Harlen Bretez, extract from The Journal of Geology, Vol. 31 No. 8, November-December 1923) The Dalles Type of River Channel (J. Harlen Bretz, extract from The Journal of Geology, Vol. 32 No. 2, February-March 1924) The Glacial Lake Missoula (J.T. Pardee, extract from The Journal of Geology, Vol. 18 No. 4, May-June 1910) The Grand Coulee of Washington: The Grand Coulee and Dry Falls in Picture and Story also Grand Coulee Dam and Columbia Basin Irrigation Project (Joseph G. McMacken, 1950) The Late Pleistocene Submergence in the Columbia Valley of Oregon and Washington (J. Harlen Bretz, extract from The Journal of Geology, Vol. 27 No. 7, October-November 1917) The Spokane Flood: A Discussion (Edwin T. McKnight, extract from The Journal of Geology, Vol. 35 No. 5, July-August 1927) The Spokane Flood: A Discussion (Olaf P. Jenkins, extract from The Journal of Geology, Vol. 33 No. 7, ) The Spokane Flood: A Reply (J. Harlen Bretz, extract from The Journal of Geology, Vol. 35 No. 5, July-August 1927) The Spokane Flood Beyond the Channeled Scablands (J. Harlen Bretz, extract from The Journal of Geology, Vol. 33 No. 2, February-March 1925) The Spokane Flood Beyond the Channeled Scablands. II (J. Harlen Bretz, extract from The Journal of Geology, Vol. 3 No. 3, April-May 1925) Topographic Effects of Glacial Lake Missoula: A Preliminary Report (Chester B. Beaty, extract from The California Geographer, 1962) Varved Lake Beds in Northern Idaho and Northeastern Washington U.S. Geological Survey Professional Paper 575-B (Eugene H. Walker, 1967) Washington's Channeled Scablands Washington Division of Mines and Geology Bulletin 45 (J. Harlen Bretz, 1959) Books | |||||
iafl/index.htm Last Updated: 01-Aug-2024 |