The Saddle Mountains consists of an upfolded

anticline In structural geology, an anticline is a type of fold that is an arch-like shape and has its oldest beds at its core, whereas a syncline is the inverse of an anticline. A typical anticline is convex up in which the hinge or crest is the ...

ridge of

basalt Basalt (; ) is an aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the surface of a rocky planet or moon. More than 90% of a ...

Grant County Grant County may refer to: Places ;Australia * County of Grant, Victoria ;United States *Grant County, Arkansas *Grant County, Indiana *Grant County, Kansas *Grant County, Kentucky *Grant County, Minnesota *Grant County, Nebraska *Grant Co ...

of central

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 ...

state. The ridge, reaching to 2,700 feet, terminates in the east south of

Othello, Washington Othello () is a city in Adams County, Washington, United States. The population was 7,364 at the 2010 census, a 26 percent increase from 2000. It is located in the heart of the Columbia Basin Project, approximately southwest of Spokane. ...

near the foot of the

Drumheller Channels 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 ...

. It continues to the west where it is broken at

Sentinel Gap Sentinel Gap is a water gap formed by the Columbia River in the Saddle Mountains, near Mattawa in Washington state. The gap is "a water gap where erosion by the Columbia River was able to keep pace with folding, faulting and uplifting across the ...

(a water gap through which the Columbia River passes) before ending in the foothills of the

Cascade Mountains The Cascade Range or Cascades is a major mountain range of western North America, extending from southern British Columbia through Washington and Oregon to Northern California. It includes both non-volcanic mountains, such as the North Cascades, ...

Saddle Mountains geology

The top exposed layer of

Columbia River Basalt Group The Columbia River Basalt Group is the youngest, smallest and one of the best-preserved continental flood basalt province on Earth, covering over mainly eastern Oregon and Washington, western Idaho, and part of northern Nevada. The basalt gro ...

basalt in the Saddle Mountains is the Saddle Mountain Basalt, which ranges from 120 – 240 meters (400 – 800 feet) in thickness and is interspersed by sedimentary layers of the Ellensburg Formation. The Saddle Mountain Basalt is composed of the Umatilla Member flows, the Wilbur Creek Member flows, the Asotin Member flows (13 million years ago), the Weissenfels Ridge Member flows, the Esquatzel Member flows, the Elephant Mountain Member flows (10.5 million years ago), the Bujford Member flows, the Ice Harbor Member flows (8.5 million years ago) and the Lower Monumental Member flows (6 million years ago). The Cordilleran Glacier diverted the ancient route of the Columbia River 15,000 years ago, backing up water to create

Lake Spokane A lake is an area filled with water, localized in a basin, surrounded by land, and distinct from any river or other outlet that serves to feed or drain the lake. Lakes lie on land and are not part of the ocean, although, like the much larger ...

. As the Okanogan lobe grew the Columbia was rerouted into the

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 Lo ...

. Flowing across the current Grand Coulee-

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 ...

region, the ice-age Columbia then entered the

Quincy Basin Quincy may refer to: People *Quincy (name), including a list of people with the name Quincy *Quincy political family, including members of the family Places and jurisdictions France *Quincy, Cher, a commune in the Cher département * A hamlet ...

near

Quincy, Washington Quincy is a city in Grant County, Washington, United States. The population was 7,543 at the 2020 census. History Geologic history Quincy lies atop a part of the Columbia River Basalt Group which is overlain by Pleistocene outburst flood de ...

and joined

Crab Creek Crab Creek is a stream in the U.S. state of Washington. Named for the presence of crayfish, it is one of the few perennial streams in the Columbia Basin of central Washington, flowing from the northeastern Columbia River Plateau, roughly east ...

at Moses Lake, following Crab Creek's course southward past the

Frenchman Hills The Frenchman Hills are hills in Grant County, Washington, United States of America. The high point is . They are an anticlinal fold in the northeastern part of the larger Yakima Fold Belt. They likely take their name for one of the first non- ...

and turning west to run along the north face of the Saddle Mountains, there to rejoin the previous and modern course of the Columbia River just above the main water gap in the Saddle Mountains,

. It eroded the north face of the Saddle Mountains, creating the conditions for the

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 ...

.J Harlen Bretz, (1923), The Channeled Scabland of the Columbia Plateau. ''Journal of Geology'', v.31, p.617-649

Geography

References

External links

Washington State Park link
* {{Authority control Mountain ranges of Washington (state) Landforms of Grant County, Washington

Saddle Mountains geology

Geography

See also

References

External links