The Ice Age Floods National Geologic Trail is a network of routes connecting natural sites and facilities that provide interpretation of the

geological Geology () is a branch of natural science concerned with Earth and other astronomical objects, the features or rocks of which it is composed, and the processes by which they change over time. Modern geology significantly overlaps all other E ...

consequences of the

Glacial Lake Missoula Lake Missoula was a prehistoric proglacial lake in western Montana that existed periodically at the end of the last ice age between 15,000 and 13,000 years ago. The lake measured about and contained about of water, half the volume of Lake Mic ...

floods A flood is an overflow of water ( or rarely other fluids) that submerges land that is usually dry. In the sense of "flowing water", the word may also be applied to the inflow of the tide. Floods are an area of study of the discipline hydrolog ...

of the last glacial period that occurred about 18,000 to 15,000 years ago. It includes sites in Washington, Oregon, Idaho, and Montana. It was designated as the first National Geologic Trail in the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...

in 2009.

History

The

National Park Service The National Park Service (NPS) is an agency of the United States federal government within the U.S. Department of the Interior that manages all national parks, most national monuments, and other natural, historical, and recreational properti ...

(NPS) commissioned an

environmental assessment Environmental Impact assessment (EIA) is the assessment of the environmental impact, environmental consequences of a plan, policy, program, or actual projects prior to the decision to move forward with the proposed action. In this context, the te ...

, which concluded that creation of a "National Geologic Trail—designating the Floods pathways managed by the National Park Service, with an Interagency Technical Committee representing the federal, tribal, and state agencies and a Trail Advisory Committee to assist the Trail Manager and staff" was the preferred option. Subsequently, the

Omnibus Public Land Management Act The Omnibus Public Land Management Act of 2009 (, ) is a land management law passed in the 111th United States Congress and signed into law by President Barack Obama on March 30, 2009. The bill designates millions of acres in the US as protected an ...

of 2009 authorized establishing the Ice Age Floods National Geologic Trail in parts of

Montana Montana () is a state in the Mountain West division of the Western United States. It is bordered by Idaho to the west, North Dakota and South Dakota to the east, Wyoming to the south, and the Canadian provinces of Alberta, British Columb ...

Idaho Idaho ( ) is a U.S. state, state in the Pacific Northwest region of the Western United States. To the north, it shares a small portion of the Canada–United States border with the province of British Columbia. It borders the states of Monta ...

Washington Washington commonly refers to: * Washington (state), United States * Washington, D.C., the capital of the United States ** A metonym for the federal government of the United States ** Washington metropolitan area, the metropolitan area centered o ...

, and

Oregon Oregon () is a U.S. state, state in the Pacific Northwest region of the Western United States. The Columbia River delineates much of Oregon's northern boundary with Washington (state), Washington, while the Snake River delineates much of it ...

and established NPS administration of the Trail.

Geologic basis for the trail

Glacial lake missoula high water mark rock 4200 ft

At the end of the last Ice Age (the Wisconsonian Ice Age), a branch of the Cordilleran Ice Sheet moved out of Canada into the Idaho panhandle region. There it formed a -high ice dam that blocked the mouth of the

Clark Fork River The Clark Fork, or the Clark Fork of the Columbia River, is a river in the U.S. states of Montana and Idaho, approximately long. The largest river by volume in Montana, it drains an extensive region of the Rocky Mountains in western Montana and ...

, creating

glacial Lake Missoula Lake Missoula was a prehistoric proglacial lake in western Montana that existed periodically at the end of the last ice age between 15,000 and 13,000 years ago. The lake measured about and contained about of water, half the volume of Lake Mic ...

, which impounded greater than of water. The lake extended up the valleys eastward for over . The periodic rupturing of the ice dam resulted in the

Missoula Floods The Missoula floods (also known as the Spokane floods or the Bretz floods or Bretz's floods) were cataclysmic glacial lake outburst floods that swept periodically across eastern Washington and down the Columbia River Gorge at the end of the las ...

– cataclysmic

flood A flood is an overflow of water ( or rarely other fluids) that submerges land that is usually dry. In the sense of "flowing water", the word may also be applied to the inflow of the tide. Floods are an area of study of the discipline hydrol ...

s that swept across Idaho and

Eastern Washington Eastern Washington is the region of the U.S. state of Washington located east of the Cascade Range. It contains the city of Spokane (the second largest city in the state), the Tri-Cities, the Columbia River and the Grand Coulee Dam, the Hanf ...

, and then down the

Columbia River Gorge The Columbia River Gorge is a canyon of the Columbia River in the Pacific Northwest of the United States. Up to deep, the canyon stretches for over as the river winds westward through the Cascade Range, forming the boundary between the st ...

approximately 40 times during a 2,000 year period. The flood front swept in a wave across Idaho and Washington at speeds approaching , and Glacial Lake Missoula drained in periods as short as 2 days. The Columbia River channel downstream was blocked by the Okanogan lobe of the Cordilleran, impounding water in

Glacial Lake Columbia Glacial Lake Columbia was the lake formed on the ice-dammed Columbia River behind the Okanogan lobe of the Cordilleran Ice Sheet when the lobe covered of the Waterville Plateau west of Grand Coulee in central Washington state during the Wis ...

. As a result, the floods could not continue down the Columbia River, being forced instead to flood over the highlands of Eastern Washington, vastly transforming the landscape by forming the Grand Coulee, Moses Coulee, the Channeled Scablands, Dry Falls, Palouse Falls and many similar features. The cumulative effect of the floods was to excavate of

loess Loess (, ; from german: Löss ) is a clastic, predominantly silt-sized sediment that is formed by the accumulation of wind-blown dust. Ten percent of Earth's land area is covered by loess or similar deposits. Loess is a periglacial or aeoli ...

, sediment and basalt from the

channeled scablands The Channeled Scablands are a relatively barren and soil-free region of interconnected relict and dry flood channels, coulees and cataracts eroded into Palouse loess and the typically flat-lying basalt flows that remain after cataclysmic floods ...

of eastern Washington and to transport it downstream. Over a period of 2,000 to 2,500 years, the repetition of ice dam failure and flood was repeated 40-60 times, leaving a lasting mark on the landscape. There are a number of characteristic features that illustrate the effect of these ice dams and power of the resulting floods: * Large portions of the scabland region of Eastern Washington were stripped bare of topsoil and left as the base basalt rock. * The landscape is extensively eroded, with deep sheer-walled canyons in the Grand Coulee, Moses Coulee, the Wallula Gap, and the Columbia River Gorge. * There are

giant ripple marks In folklore, giants (from Ancient Greek: '' gigas'', cognate giga-) are beings of human-like appearance, but are at times prodigious in size and strength or bear an otherwise notable appearance. The word ''giant'' is first attested in 1297 fro ...

high and gravel bars over long and high, which would have required extreme currents to form. * There are erratic boulders which originated in Canada and Montana, found well up valleys such as the

Willamette River The Willamette River ( ) is a major tributary of the Columbia River, accounting for 12 to 15 percent of the Columbia's flow. The Willamette's main stem is long, lying entirely in northwestern Oregon in the United States. Flowing northward b ...

valley far south of any evidence of glacial activity; these boulders were ice rafted in and deposited as the ice was stranded & melted in backwaters of temporary lakes. * The scablands formed include deep kolks formed by local turbulence, which plucked basalt boulders out and excavated pits in the middle of relatively smooth plains. * Backwaters of temporary lakes formed during the floods show extensive & periodic deposits of silt and sand.

Trail features

Glacial lake missoula high water mark rock 4200 ft trail

The trail comprises routes throughout the Pacific Northwest where the Ice Age Floods left a lasting impact. Regions and featured sites include * The

region in Montana in which the waters were initially impounded * The

Lake Coeur d'Alene Lake Coeur d'Alene, officially Coeur d'Alene Lake ( ), is a natural dam-controlled lake in North Idaho, located in the Pacific Northwest region of the United States. At its northern end is the city of Coeur d'Alene. It spans in length and rang ...

area and

Clark Fork river The Clark Fork, or the Clark Fork of the Columbia River, is a river in the U.S. states of Montana and Idaho, approximately long. The largest river by volume in Montana, it drains an extensive region of the Rocky Mountains in western Montana and ...

of Idaho through which the flood waters periodically flowed ** Farragut State Park **

Lake Pend Oreille Lake Pend Oreille ( ) in the northern Idaho Panhandle is the largest lake in the U.S. state of Idaho and the 38th-largest lake by area in the United States, with a surface area of . It is long, and deep in some regions, making it the fifth-deep ...

* The Waterville Plateau in Washington state where the Okanagon lobe impounded

and diverted the flow through

Moses Coulee Moses Coulee is a canyon in the Waterville plateau region of Douglas County, Washington. Moses Coulee is the second-largest and westernmost canyon of the Channeled Scablands, located about to the west of the larger Grand Coulee. This water channe ...

Grand Coulee Grand Coulee is an ancient river bed in the U.S. state of Washington. This National Natural Landmark stretches for about 60 miles (100 km) southwest from Grand Coulee Dam to Soap Lake, being bisected by Dry Falls into the Upper and Lower ...

and

Dry Falls Dry Falls is a scalloped precipice with four major alcoves, in central Washington scablands. This cataract complex is on the opposite side of the Upper Grand Coulee from the Columbia River, and at the head of the Lower Grand Coulee, northern ...

**The Withrow Moraine and Jameson Lake Drumlin Field ** Boulder Park ** Sims Corner Eskers and Kames * Erosion features from the floods such as the

Channeled Scablands The Channeled Scablands are a relatively barren and soil-free region of interconnected relict and dry flood channels, coulees and cataracts eroded into Palouse loess and the typically flat-lying basalt flows that remain after cataclysmic floods ...

, Drumheller Channels, Crab Creek,

Corfu Slide The Corfu Slide is a geological feature located on the north slope of the Saddle Mountains above Crab Creek near the Columbia River in eastern Washington. It consists of 24 separate slides that cover approximately 18-20 square kilometers (7 to 8 ...

and

Palouse Falls Palouse Falls is a waterfall on the Palouse River, about upstream of the confluence with the Snake River in southeast Washington, United States. The falls are in height. The falls consist of an upper fall with a drop around , which lies north ...

in Washington ** Sun Lakes-Dry Falls State Park **

Ginkgo Petrified Forest State Park Ginkgo Petrified Forest State Park/Wanapum Recreational Area is a geologic preserve and public recreation area covering on the western shoreline of the Columbia River's Wanapum Reservoir at Vantage, Washington. Petrified wood was discovered in t ...

** Lyons Ferry State Park ** Steamboat Rock State Park * Temporary lakes such as

Lake Lewis Lake Lewis was a temporary lake in the Pacific Northwest region of North America, largely formed by the Missoula Floods in about the 14th millennium B.C. Lake Lewis was formed when the restricted flow of waters from periodic cataclysmic floods f ...

in Washington as well as Lake Condon and

Lake Allison Lake Allison was a temporary lake in the Willamette Valley of Oregon, formed periodically by the Missoula Floods from 15,000 to 13,000 BC. The lake is the main cause of the rich and fertile soil that now characterizes the Willamette Valley. Histo ...

in Oregon and the evidence for these temporary lakes as seen in the ice rafted erratics and in the deposits of the

Touchet Formation The Touchet Formation or Touchet beds consist of large quantities of gravel and fine sediment which overlay almost a thousand meters (several thousand feet) of volcanic basalt of the Columbia River Basalt Group in south-central Washington (U.S. ...

Yakima Sportsman State Park Yakima Sportsman State Park is a public recreation area located on the Yakima River on the east side of the city of Yakima in Yakima County, Washington. The state park is an oasis of green in an otherwise desert region, encompassing of Yakima ...

**Bellevue Erratic * Erosion features such as the

Wallula Gap Wallula Gap () is a large water gap of the Columbia River in the northwest United States in southeast Washington. It cuts through the Horse Heaven Hills basalt anticlines in the Columbia River Basin, just south of the confluence of the Wa ...

through the

Horse Heaven Hills The Horse Heaven Hills are a long range of high, rolling hills in Klickitat, Yakima, and Benton counties in Washington. The hills are an anticline ridge in the Yakima Fold Belt formed by north–south compression of lava flows in the Columbi ...

in southern Washington, the

on the border between Oregon and Washington and

Alameda Ridge The Alameda Ridge is a large gravel bar located in Portland, Oregon, United States. It forms a ridgeline above much of north and southeast Portland, with views of downtown and west side neighborhoods. Alameda Ridge runs through the Madison Sout ...

in Portland. **

Columbia Hills State Park Columbia Hills State Park is a Washington state park located east of Dallesport on SR 14 in Klickitat County. The park occupies on Horsethief Lake, an impoundment of the Columbia River, and was created in 2003 with the merger of Horsethief ...

** Beacon Rock State Park **

Multnomah Falls Multnomah Falls is a waterfall located on Multnomah Creek in the Columbia River Gorge, east of Troutdale, between Corbett and Dodson, Oregon, United States. The waterfall is accessible from the Historic Columbia River Highway and Interstate 84. ...

** Portland Women's Forum ** Vista House Several museums in the region feature local aspects of the natural history of the floods.

References

External links

Ice Age Floods InstituteIce Age Floods National Geologic Trail Long-range Interpretive Plan

Resource Study of Alternatives
{{Coord missing, Idaho National Trails of the United States Protected areas established in 2009 Historical geology Ice ages Protected areas of the United States

History

Geologic basis for the trail

Trail features

See also

References

External links