The Yakima Fold Belt of south-central Washington, also called the Yakima fold-and-thrust belt, is an area of topographical folds (or wrinkles) raised by tectonic compression. It is a structural-tectonic sub province of the western

Columbia Plateau The Columbia Plateau is a geologic and geographic region that lies across parts of the U.S. states of Washington, Oregon, and Idaho. It is a wide flood basalt plateau between the Cascade Range and the Rocky Mountains, cut through by the Co ...

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 (immediately northwest of the Tri-Cities) and major dams on the Columbia and Snake Rivers.

Location and extent

Image:Yakima Fold Belt map.jpg, upright=1.34, Shaded-relief map showing ridges of the Yakima Fold Belt of south-central Washington, mostly between

Interstate 90 Interstate 90 (I-90) is an east–west transcontinental freeway and the longest Interstate Highway in the United States at . It begins in Seattle, Washington, and travels through the Pacific Northwest, Mountain West, Great Plains, Midwest, a ...

(red line) and the Columbia River (bottom). Red square in center is the city of

Yakima Yakima ( or ) is a city in and the county seat of Yakima County, Washington, and the state's 11th-largest city by population. As of the 2020 census, the city had a total population of 96,968 and a metropolitan population of 256,728. The uni ...

, red rectangle at lower right is the

Tri-Cities Tri-Cities most often refers to: *Tri-Cities, Tennessee, United States *Tri-Cities, Washington, United States Tri-City, Tricity or Tri-Cities may also refer to: Populated places Americas Canada *Tri-Cities (British Columbia), consisting of Co ...

, red circles are various cities, triangles are the

Mount Rainier Mount Rainier (), indigenously known as Tahoma, Tacoma, Tacobet, or təqʷubəʔ, is a large active stratovolcano in the Cascade Range of the Pacific Northwest, located in Mount Rainier National Park about south-southeast of Seattle. With a ...

, Mount St. Helens, and Mount Adams volcanoes of the Southern Washington Cascades. Purple dashed line marks the approximate location of the Olympic–Wallowa Lineament (OWL), crossing the Columbia River at 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 ...

(lower-right). Orange dashed line is approximate location of edge of the North American craton. The smoothness of the central and eastern areas is due to infilling by volcanic flows of the Columbia River Basalts. # Image size: 641x458 (642x459) # # In error messages: imagemap line numbers include comment lines. # This should be line 5. # Areas defined first overlap areas defined later. (??) # Cities and towns: # Localized regions and lakes: circle 180 16 16 Lake Keechelus circle 204 24 20

Lake Kachess Kachess Lake () is a lake and reservoir along the course of the Kachess River in Washington state, US. The upper part of the lake, north of a narrows, is called Little Kachess Lake. The Kachess River flows into the lake from the north, and out fr ...

circle 224 34 16

Lake Cle Elum Cle Elum Lake is a lake and reservoir along the course of the Cle Elum River, in Washington state USA. At the site of the future city of Cle Elum, Washington, a Northern Pacific Railway station was named Clealum after the Kittitas name Tle-el-Lum ...

circle 254 56 16

Cle Elum Cle Elum ( ) is a city in Kittitas County, Washington, United States. The population was 1,872 at the 2010 census. About by car from Seattle, Cle Elum is a popular area for camping and outdoor activities. History Native history Cle Elum wa ...

circle 314 100 16

Ellensburg Ellensburg is a city in and the county seat of Kittitas County, Washington, United States. It is located just east of the Cascade Range near the junction of Interstate 90 and Interstate 82. The population was 18,666 at the 2020 census. and ...

circle 434 48 16 Quincy circle 480 24 16 Ephrata circle 522 76 20

Moses Lake Moses Lake is a lake and reservoir along the course of Crab Creek, in Washington state, USA. Moses Lake is part of the Columbia River basin, as Crab Creek is a tributary of the Columbia River. Although originally a shallow natural lake, Mose ...

circle 506 92 20 Pot Holes Reservoir circle 538 140 16

Othello ''Othello'' (full title: ''The Tragedy of Othello, the Moor of Venice'') is a tragedy written by William Shakespeare, probably in 1603, set in the contemporary Ottoman–Venetian War (1570–1573) fought for the control of the Island of Cyp ...

circle 320 200 16

circle 324 214 12 Union Gap circle 570 326 16

circle 262 378 16

Goldendale Goldendale is a city and county seat of Klickitat County, Washington, United States, near the Columbia River Gorge. The population within city limits was 3,760 at the 2000 census and 3,407 at the 2010 census, a 9.4% decrease. It is situated i ...

circle 212 434 16

The Dalles The Dalles is the largest city of Wasco County, Oregon, United States. The population was 16,010 at the 2020 census, and it is the largest city on the Oregon side of the Columbia River between the Portland Metropolitan Area, and Hermist ...

circle 156 406 16 Hood River poly 1 30 12 32 12 46 1 46 Tacoma poly 510 264 558 264 558 292 510 292

# circle 120 134 22

circle 56 294 22 Mount St. Helens circle 164 288 22 Mount Adams # Dams: poly 374 14 386 6 394 16 382 24

Rock Island Dam Rock Island Dam is a hydroelectric dam on the Columbia River, in the U.S. state of Washington. Chelan County Public Utility District's ''Rock Island Dam and Hydro Project'' was the first dam to span the Columbia, having been built from 1929 ...

circle 408 134 16 Wanapum Dam circle 418 184 16 Priest Rapids Dam circle 582 278 16

Ice Harbor Dam Ice Harbor Lock and Dam is a hydroelectric, concrete gravity run-of-the-river dam in the northwest United States. On the lower Snake River in southeastern Washington, it bridges Walla Walla and Franklin counties. Located northeast of Bu ...

circle 502 354 16 McNary Dam circle 290 402 16 John Day Dam circle 224 422 16

The Dalles Dam The Dalles Dam is a concrete-gravity run-of-the-river dam spanning the Columbia River, two miles (3 km) east of the city of The Dalles, Oregon, United States. It joins Wasco County, Oregon with Klickitat County, Washington, 300 miles (309&n ...

circle 102 408 16

Bonneville Dam Bonneville Lock and Dam consists of several run-of-the-river dam structures that together complete a span of the Columbia River between the U.S. states of Oregon and Washington at River Mile 146.1. The dam is located east of Portland, Or ...

# poly 72 48 140 52 160 90 152 122 142 126 146 108 132 64 88 66 White River # The Folds: poly 232 30 260 32 292 56 280 64 268 58 235 40 Cle Elum Ridge poly 238 64 252 60 278 74 274 82 260 74 244 74 South Cle Elum Ridge poly 224 80 242 82 286 104 306 106 378 144 380 160 298 118 272 118 232 100

Manastash Ridge Manastash Ridge is a long anticline mountain ridge A ridge or a mountain ridge is a geographical feature consisting of a chain of mountains or hills that form a continuous elevated crest for an extended distance. The sides of the ridge s ...

poly 282 122 300 124 382 172 422 188 442 190 436 198 420 196 404 192 380 190 314 142 296 140 280 128

Umtanum Ridge 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 ...

poly 336 92 356 100 374 122 366 126 348 118

Boylston Mountains Boylston may refer to the following communities: ;Canada * Boylston, Nova Scotia ;United States * Boylston, Massachusetts * Boylston, New York * Boylston, Wisconsin * Boylston Junction, Wisconsin It may also refer to: * Helen Dore Boylston, auth ...

poly 382 2 410 2 396 20 Badger Mountain poly 404 22 422 2 478 2 470 30 406 32

Beezley Hills The Beezley Hills are a range of hills, about north of Quincy in Grant County, Washington with a maximum elevation of or . The city of Ephrata, Washington, at the east end of the hills, was originally called Beezley Springs, named after hors ...

poly 364 130 376 126 420 138 470 138 520 146 548 166 540 178 514 160 418 156 392 148

Saddle Mountains 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 Channel ...

poly 380 100 406 92 512 106 526 112 516 120 386 110

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- ...

poly 470 184 494 188 502 206 594 208 472 198

Gable Mountain Gable Mountain () is located in the Lewis Range, Glacier National Park in the U.S. state of Montana. Gable Mountain is in the northeastern section of Glacier National Park, approximately southwest of the prominent Chief Mountain. See also * ...

poly 250 124 266 126 284 148 290 158 278 158 254 142 Cleman Mountain poly 322 182 344 178 380 192 404 194 452 212 446 222 416 210 382 216 336 200

Yakima Ridge 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 ea ...

poly 210 166 352 150 268 162 246 176 226 174 Bethel Ridge poly 252 194 272 182 310 190 306 198 276 196 360 204 Cowiche Mountain poly 218 222 248 204 254 208 246 214 224 230 #Sedge Ridge poly 226 232 258 208 320 208 298 228 260 224 230 240 Ahtanum Ridge poly 232 210 248 208 380 220 412 216 446 230 464 230 480 256 436 274 334 218 Rattlesnake Hills poly 198 290 310 260 368 258 366 268 296 294 198 300 Toppenish Ridge poly 370 254 398 262 390 268

Snipes Mountain Snipes Mountain AVA is an American Viticultural Area located in the Yakima Valley of Washington State. It was approved by the Bureau of Alcohol, Tobacco, Firearms and Explosives on January 21, 2009 making it Washington's 10th federally designat ...

poly 314 324 394 306 474 274 515 309 546 310 552 320 542 326 496 320 468 304 402 328 330 330 Horse Heaven Hills circle 266 336 22 #Simcoe Mountain poly 300 334 352 334 344 346 294 348 #Bickleton Ridge poly 204 402 300 380 332 386 330 396 300 392 258 416 208 416

Columbia Hills (Washington) The Columbia Hills are an area of hills and small mountains along the north bank of the Columbia River in Klickitat County, in south-central Washington (state), USA. They have a maximum elevation of . Columbia Hills Historical State Park Columb ...

poly 448 352 466 338 512 330 510 346 470 350 454 356 #Paterson Ridge circle 492 266 16 #Red Mountain # Broader regions: poly 72 1 186 1 640 336 640 386 418 212 316 190 Olympic–Wallowa Lineament poly 510 109 528 100 612 334 594 334 #craton edge poly 296 2 322 2 380 52 392 188 376 182 366 98 356 60 304 24 #Naneum-Hog Ranch Anticline ### The topographical distinctness of the Yakima Folds (see the shaded-relief image) is due to their formation in a layer of

lava flows Lava is molten or partially molten rock ( magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land o ...

and sedimentary deposits that have filled-in and generally smoothed the topographic surface of a large area of the Columbia Basin. The extent of these lava flows was limited to the west and north by the rising

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, ...

and the

Wenatchee Mountains The Wenatchee Mountains are a range of mountains in central Washington State, United States of America. A major subrange of the Cascade Range, extending east from the Cascade crest, the Wenatchee Mountains separate the drainage basins of the ...

. The lava flows extend east well beyond this image, but the Yakima Folds do not. The northernmost fold seen hereSome researchers include structures north of this image. (Frenchman Hills) ends at the Potholes Reservoir, another (Saddle Mountains) terminates just south of there, near the town of

(red circle). South of the Tri-Cities the rampart of the Horse Heaven Hills extends for a short distance past the Columbia River. The ends of these ridges mark the edge of a block of continental crust (part of the North American craton, indicated by the dashed orange line) that has resisted the tectonic compression that formed the ridges. The southernmost ridge of the Yakima Fold Belt is the Columbia Hills on the north side of the Columbia River. The pattern of folding continues with the Dalles-Umatilla Syncline just south of the Columbia River, and further into Oregon with the Blue Mountains anticline, which approximately parallels the Klamath-Blue Mountain Lineament that marks the southeastern edge of

Siletzia Siletzia is a massive formation of early to middle Eocene epoch marine basalts and interbedded sediments in the forearc of the Cascadia subduction zone, on the west coast of North America. It forms the basement rock under western Oregon ...

(see geological map, below). The Yakima Fold Belt is also located on, and the orientation and spacing of some of the Folds influenced by, the Olympic–Wallowa Lineament (OWL), a broad zone of linear topographical features (dashed yellow line) extending from the Olympic Peninsula in northwestern Washington to the Wallowa Mountains in northeastern Oregon.

Geology

It is the central portion of the Olympic–Wallowa Lineament, referred to as the Cle Elum-Wallula deformed zone (CLEW), constising of a series of generally east-trending narrow asymmetrical

anticlinal Anticlinal may refer to: *Anticline, in structural geology, an anticline is a fold that is convex up and has its oldest beds at its core. *Anticlinal, in stereochemistry, a torsion angle between 90° to 150°, and –90° to –150°; see Alkane_st ...

ridges and broad synclinal valleys formed by folding of

Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recent" ...

Columbia River basalt flows and sediments. In most parts of the belt the folds have a north

vergence A vergence is the simultaneous movement of both eyes in opposite directions to obtain or maintain single binocular vision. When a creature with binocular vision looks at an object, the eyes must rotate around a vertical axis so that the projec ...

(Columbia Hills' south vergence is an exception) with the steep limb typically faulted by imbricate

thrust fault A thrust fault is a break in the Earth's crust, across which older rocks are pushed above younger rocks. Thrust geometry and nomenclature Reverse faults A thrust fault is a type of reverse fault that has a dip of 45 degrees or less. If ...

s. Fold lengths range from 1 km to 100 km with wavelengths from several kilometers to 20 km. A

graben In geology, a graben () is a depressed block of the crust of a planet or moon, bordered by parallel normal faults. Etymology ''Graben'' is a loan word from German, meaning 'ditch' or 'trench'. The word was first used in the geologic contex ...

underlies nearly the entire Yakima Fold Belt and has been subsiding since

Eocene The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', " ...

time, and continues to sink at a slow rate. A 2011 report found aeromagnetic,

gravity In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the str ...

, and

paleoseismic Paleoseismology looks at geologic sediments and rocks, for signs of ancient earthquakes. It is used to supplement seismic monitoring, for the calculation of seismic hazard. Paleoseismology is usually restricted to geologic regimes that have u ...

evidence that the Yakima Fold Belt is linked to active Puget Sound faults.

Geodesy

Geodetic studies of the Oregon Rotation show that Oregon is rotating about a point somewhat south of

Lewiston, Idaho Lewiston is a city and the county seat of Nez Perce County, Idaho, United States, in the state's north central region. It is the second-largest city in the northern Idaho region, behind Coeur d'Alene, and ninth-largest in the state. Lewiston i ...

compressing the Yakima fold an average of 3 millimeters per year, and the Washington Pacific coast about 7 millimeters per year. Studies of the motion of the Yakima Fold Belt have been undertaken to evaluate seismic hazards at the

Hanford Site The Hanford Site is a decommissioned nuclear production complex operated by the United States federal government on the Columbia River in Benton County in the U.S. state of Washington. The site has been known by many names, including SiteW ...

Notes and sources

Notes

Sources

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