Ahtanum Ridge is a long anticline

Anticline

In structural geology, an anticline is a fold that is convex up and has its oldest beds at its core. The term is not to be confused with antiform, which is a purely descriptive term for any fold that is convex up. Therefore if age relationships In structural geology, an anticline is a fold that is...

 mountain

Mountain

Image:Himalaya_annotated.jpg|thumb|right|The Himalayan mountain range with Mount Everestrect 58 14 160 49 Chomo Lonzorect 200 28 335 52 Makalurect 378 24 566 45 Mount Everestrect 188 581 920 656 Tibetan Plateaurect 250 406 340 427 Rong River...

 ridge

Ridge

A ridge is a geological feature consisting of a chain of mountains or hills that form a continuous elevated crest for some distance. Ridges are usually termed hills or mountains as well, depending on size. There are several main types of ridges:...

 in Yakima County

Yakima County, Washington

Yakima County is the second largest county by area in the U.S. state of Washington. It is named after the Yakama tribe of Native Americans. In the 2010 census, its population was 243,231...

 in the U.S. state

U.S. state

A U.S. state is any one of the 50 federated states of the United States of America that share sovereignty with the federal government. Because of this shared sovereignty, an American is a citizen both of the federal entity and of his or her state of domicile. Four states use the official title of...

 of Washington. It is located just south of the city of Yakima

Yakima, Washington

Yakima is an American city southeast of Mount Rainier National Park and the county seat of Yakima County, Washington, United States, and the eighth largest city by population in the state itself. As of the 2010 census, the city had a total population of 91,196 and a metropolitan population of...

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Ahtanum Ridge is part of the Yakima Fold Belt of east-tending long ridges formed by the folding of Miocene

Miocene

The Miocene is a geological epoch of the Neogene Period and extends from about . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene...

 Columbia River basalt flows

Columbia River Basalt Group

The Columbia River Basalt Group is a large igneous province that lies across parts of the Western United States. It is found in the U.S. states of Washington, Oregon, Idaho, Nevada, and California...

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Ahtanum Ridge separates Yakima Valley

Yakima River

The Yakima River is a tributary of the Columbia River in south central and eastern Washington State, named for the indigenous Yakama people. The length of the river from headwaters to mouth is , with an average drop of .-Course:...

 on the south from Ahtanum Valley on the north. At the eastern end of Ahtanum Ridge the Yakima River

Yakima River

The Yakima River is a tributary of the Columbia River in south central and eastern Washington State, named for the indigenous Yakama people. The length of the river from headwaters to mouth is , with an average drop of .-Course:...

 flows through Union Gap. The ridge continues east of Union Gap

Union Gap, Washington

Union Gap is a city in Yakima County, Washington, in the United States. As of the 2010 census, the city population was 6,047.-History:The city of Union Gap was originally named Yakima and was officially incorporated on November 23, 1883...

 as the Rattlesnake Hills

Rattlesnake Hills

The Rattlesnake Hills is a 16 mile long anticline mountain ridge in Yakima County and Benton County in the U.S. state of Washington. Also known as Rattlesnake Mountain and Rattlesnake Ridge, it should not be confused with the much smaller Rattlesnake Ridge located near the west end of Ahtanum Ridge...

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