Pentagon Mountain is an mountain summit located in Flathead County of the

U.S. state In the United States, a state is a constituent political entity, of which there are 50. Bound together in a political union, each state holds governmental jurisdiction over a separate and defined geographic territory where it shares its sover ...

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 Columbi ...

Description

Pentagon Mountain is the highest point in the Trilobite Range, which is a subset of the

Flathead Range The Flathead Range is a mountain range of the Northern Rocky Mountains located southeast of Whitefish, Montana in the Great Bear Wilderness, part of the Bob Marshall Wilderness Complex. It is west of the Rocky Mountain Front, east of the Swan Ra ...

. It is set within the

Bob Marshall Wilderness The Bob Marshall Wilderness Area is a congressionally-designated wilderness area located in Western Montana region of the United States. It is named after Bob Marshall (1901–1939), an early forester in the federal government, conservationist, a ...

, on land managed by

Flathead National Forest The Flathead National Forest is a national forest in the western part of the U.S. state of Montana. The forest lies primarily in Flathead County, south of Glacier National Park. The forest covers of which about is designated wilderness. It i ...

. It is situated two miles west of the

Continental Divide A continental divide is a drainage divide on a continent such that the drainage basin on one side of the divide feeds into one ocean or sea, and the basin on the other side either feeds into a different ocean or sea, or else is endorheic, not ...

, and

topographic relief Terrain or relief (also topographical relief) involves the vertical and horizontal dimensions of land surface. The term bathymetry is used to describe underwater relief, while hypsometry studies terrain relative to sea level. The Latin word ...

is significant as the summit rises approximately above Pentagon Creek in approximately one mile. Precipitation

runoff Runoff, run-off or RUNOFF may refer to: * RUNOFF, the first computer text-formatting program * Runoff or run-off, another name for bleed, printing that lies beyond the edges to which a printed sheet is trimmed * Runoff or run-off, a stock market ...

from the mountain drains west and south to the Spotted Bear River via Pentagon Creek, and north to the

Middle Fork Flathead River The Middle Fork Flathead River is a river in western Montana in the United States, forming the southwestern boundary of Glacier National Park. Its drainage basin lies to the east of the South Fork Flathead River and the Hungry Horse Reservoir. ...

via Clack Creek. The nearest higher neighbor is Three Sisters, to the south.

Climate

Based on the

Köppen climate classification The Köppen climate classification is one of the most widely used climate classification systems. It was first published by German-Russian climatologist Wladimir Köppen (1846–1940) in 1884, with several later modifications by Köppen, notabl ...

, Pentagon Mountain is located in a

subarctic climate The subarctic climate (also called subpolar climate, or boreal climate) is a climate with long, cold (often very cold) winters, and short, warm to cool summers. It is found on large landmasses, often away from the moderating effects of an ocean, ge ...

zone characterized by long, usually very cold winters, and short, cool to mild summers. Winter temperatures can drop below −10 °F with wind chill factors below −30 °F.

Geology

Pentagon Mountain is composed of

sedimentary rock Sedimentary rocks are types of rock that are formed by the accumulation or deposition of mineral or organic particles at Earth's surface, followed by cementation. Sedimentation is the collective name for processes that cause these particles ...

laid down during the

Precambrian The Precambrian (or Pre-Cambrian, sometimes abbreviated pꞒ, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of the ...

Jurassic The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The J ...

periods. Formed in shallow seas, this sedimentary rock was initially uplifted beginning 170 million years ago when the

Lewis Overthrust The Lewis Overthrust is a geologic thrust fault structure of the Rocky Mountains found within the bordering national parks of Glacier in Montana, United States and Waterton Lakes in Alberta, Canada. The structure was created due to the collision of ...

fault pushed an enormous slab of

precambrian The Precambrian (or Pre-Cambrian, sometimes abbreviated pꞒ, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of the ...

rocks thick, wide and long over younger rock of the

cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...

period.

Gallery

File:20190329-FS-FlatheadNF-YFYF-060 (47524699081).jpg, Aerial of east aspect, Dean Lake to left. File:20190329-FS-FlatheadNF-YFYF-059 (47524701251).jpg

References

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External links