The Missoula floods were cataclysmic glacial lake outburst floods that swept periodically across eastern Washington and down the Columbia River Gorge at the end of the last ice age. These floods were the result of periodic sudden ruptures of the ice dam on the Clark Fork River that created Glacial Lake Missoula. After each ice dam rupture, the waters of the lake would rush down the Clark Fork and the Columbia River, flooding much of eastern Washington and the Willamette Valley in western Oregon. After the lake drained, the ice would reform, creating Glacial Lake Missoula again.
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 7,770 square kilometres (3,000 sq mi) and contained about 2,100 cubic kilometres (500 cu mi) of water, half the volume of Lake Michigan.
U.S. Route 97 (US 97) is a major north–south route of the United States Numbered Highway System in the Pacific Northwest region. It runs for approximately 670 miles (1,078 km) through the states of California, Oregon, and Washington, primarily serving interior areas on the east side of the Cascade Mountains. The highway terminates to the south at a junction with Interstate 5 (I-5) in Weed, California, and to the north at the Canadian border near Osoyoos, British Columbia, where it becomes British Columbia Highway 97. Major cities on the US 97 corridor include Klamath Falls, Bend, and Redmond in Oregon; and Yakima, Ellensburg, and Wenatchee in Washington. A portion of the highway in California and Oregon is part of the Volcanic Legacy Scenic Byway.
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 Grand Coulee.
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 within the southeastern part of Washington state. The Channeled Scablands were scoured by more than 40 cataclysmic floods during the Last Glacial Maximum and innumerable older cataclysmic floods over the last two million years. These floods were periodically unleashed whenever a large glacial lake broke through its ice dam and swept across eastern Washington and down the Columbia River Plateau during the Pleistocene epoch. The last of the cataclysmic floods occurred between 18,200 and 14,000 years ago.
The Palouse River is a tributary of the Snake River in Washington and Idaho, in the northwest United States. It flows for 167 miles (269 km) southwestwards, primarily through the Palouse region of southeastern Washington. It is part of the Columbia River Basin, as the Snake River is a tributary of the Columbia River.
Manastash Ridge is a long anticline mountain ridge located in central Washington state in the United States. Manastash Ridge runs mostly west-to-east in Kittitas and Yakima counties, for approximately 50 miles. The ridge is part of the Yakima Fold Belt of east-tending long ridges formed by the folding of Miocene Columbia River basalt flows.
Wallula Gap is a large water gap of the Columbia River in the Northwestern United States, in Southeastern Washington. It cuts through the Horse Heaven Hills basalt anticlines in the Columbia River Basin, just south of the confluence of the Walla Walla and Columbia rivers.
The Touchet Formation or Touchet beds consist of well-bedded, coarse to fine sand and silt which overlays local bedrock composed of Neogene basalt of the Columbia River Basalt Group in south-central Washington and north-central Oregon. The beds consist of more than 40 to 62 distinct rhythmites – horizontal layers of sediment, each clearly demarcated from the layer below. These Touchet beds are often covered by windblown loess which were deposited later; the number of layers varies with location. The beds vary in thickness from 330 ft (100 m) at lower elevations where a number of layers can be found to a few extremely thin layers at the maximum elevation where they are observed.
Lake Lewis was a large transient lake in the Pacific Northwest region of North America, formed by periodic Missoula Floods along the Columbia River paleocourse between 21,000 and 16,000 years ago.
Drumheller Channels National Natural Landmark showcases the Drumheller Channels, which are the most significant example in the Columbia Plateau of basalt butte-and-basin Channeled Scablands. This National Natural Landmark is an extensively eroded landscape, located in south central Washington state characterized by hundreds of isolated, steep-sided hills (buttes) surrounded by a braided network of numerous channels, all but one of which are currently dry. It is a classic example of the tremendous erosive powers of extremely large floods such as those that reformed the Columbia Plateau volcanic terrain during the late Pleistocene glacial Missoula Floods.
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 30 kilometres (19 mi) to the west of the larger Grand Coulee. This water channel is now dry, but during glacial periods, large outburst floods with discharges greater than 600,000 m3/s (21,000,000 cu ft/s) carved the channel. While it's clear that glacial floodwaters passed through and contributed to the erosion of Moses Coulee, the age of those waters, thus the origins of the coulee are less clear. No clear connection between the head of the coulee and major flood routes to the north, east, or west is known. Some researchers propose that floods from glacial Lake Missoula formed Moses Coulee, while others suggest that subglacial floods from the Okanogan Lobe incised the canyon. The mouth of Moses Coulee discharges into the Columbia River.
State Route 821 (SR 821) is a state highway in central Washington state. It runs for 25 miles (40 km) through the Yakima Canyon, following the meandering Yakima River between Selah and Ellensburg. Both ends of the highway are at interchanges with Interstate 82 (I-82) and U.S. Route 97 (US 97).
The Saddle Mountains consists of an upfolded anticline ridge of basalt in Grant County of central Washington state. The ridge, reaching to 2,700 feet, terminates in the east south of Othello, Washington near the foot of the Drumheller Channels. It continues to the west where it is broken at Sentinel Gap before ending in the foothills of the Cascade Mountains.
U.S. Route 97 in the U.S. state of Washington is a 322-mile (518 km) route which traverses from the Oregon state line at the northern end of the Sam Hill Memorial Bridge in Maryhill, north to the Canada–US border in Okanogan County near Oroville. The highway serves major cities such as Goldendale, Yakima, Ellensburg and Wenatchee before continuing towards the Alaska Highway at the Yukon border as British Columbia Highway 97. Along the length of the roadway, US 97 is concurrent with State Route 14 in Maryhill, Interstate 82 (I-82) and US 12 between Union Gap and Ellensburg, I-90 briefly in Ellensburg, US 2 between Peshastin and rural Douglas County and SR 20 near Omak. An alternate route connects the highway with Chelan.
The Columbia Plateau ecoregion is a Level III ecoregion designated by the United States Environmental Protection Agency (EPA) encompassing approximately 32,100 square miles (83,139 km2) of land within the U.S. states of Washington, Oregon, and Idaho. The ecoregion extends across a wide swath of the Columbia River Basin from The Dalles, Oregon to Lewiston, Idaho to Okanogan, Washington near the Canada–U.S. border. It includes nearly 500 miles (800 km) of the Columbia River, as well as the lower reaches of major tributaries such as the Snake and Yakima rivers and the associated drainage basins. It is named for the Columbia Plateau, a flood basalt plateau formed by the Columbia River Basalt Group during the late Miocene and early Pliocene. The arid sagebrush steppe and grasslands of the region are flanked by moister, predominantly forested, mountainous ecoregions on all sides. The underlying basalt is up to 2 miles (3 km) thick and partially covered by thick loess deposits. Where precipitation amounts are sufficient, the deep loess soils have been extensively cultivated for wheat. Water from the Columbia River is subject to resource allocation debates involving fisheries, navigation, hydropower, recreation, and irrigation, and the Columbia Basin Project has dramatically converted much of the region to agricultural use.
Umtanum Ridge is a long anticline mountain ridge in Yakima County and Kittitas County in the U.S. state of Washington. It runs for approximately 55 miles east-southeast from the Cascade Range, through the Yakima Training Center to the edge of the Columbia River at Priest Rapids Dam and Hanford Reach. The eastern end of Umtanum Ridge enters Hanford Reach National Monument and the Hanford Site. Umtanum Ridge is paralleled on the north by Manastash Ridge and on the south by Yakima Ridge. The Yakima River cuts through the ridge at the Umtanum Ridge Water Gap.
Yakima Ridge is a long anticline mountain ridge in Yakima County and Benton County in the U.S. state of Washington. From its western end just north of the city of Yakima, the ridge runs east-southeast through the Yakima Training Center to its eastern end at Hanford Reach National Monument and the Hanford Site. Yakima Ridge is paralleled on the north by Umtanum Ridge and on the south by the Rattlesnake Hills. Moxee Valley and Black Rock Valley lie south of Yakima Ridge.
The Ice Age Floods National Geologic Trail is a network of routes connecting natural sites and facilities that provide interpretation of the geological consequences of the Glacial Lake Missoula floods 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 in 2009.
The Yakima Fold Belt of south-central Washington, also called the Yakima fold-and-thrust belt, is an area of topographical folds raised by tectonic compression. It is a 14,000 km2 (5,400 sq mi) structural-tectonic sub province of the western Columbia Plateau Province resulting from complex and poorly understood regional tectonics. The folds are associated with geological faults whose seismic risk is of particular concern to the nuclear facilities at the Hanford Nuclear Reservation and major dams on the Columbia and Snake Rivers.
