The 1925 Montana (Clarkston Valley) earthquake occurred at 17:21:12 MDT on 27 June in

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 Columb ...

, with the epicenter being located near

Townsend Townsend (pronounced tounʹ-zənd) or Townshend may refer to: Places United States *Camp Townsend, National Guard training base in Peekskill, New York *Townsend, Delaware *Townsend, Georgia *Townsend, Massachusetts, a New England town ** Townsend ...

. The earthquake had a magnitude of 6.9 in the surface wave magnitude scale. A maximum intensity of IX ''(Violent)'' was observed. Serious damage was reported near the epicenter. 3 hours after the mainshock, a strong aftershock was recorded with an unknown magnitude that also caused damage.

Tectonic setting

The epicenter area, Clarkston Valley is a

valley A valley is an elongated low area often running between hills or mountains, which will typically contain a river or stream running from one end to the other. Most valleys are formed by erosion of the land surface by rivers or streams ove ...

surrounded by mountains of severely folded

Mesozoic The Mesozoic Era ( ), also called the Age of Reptiles, the Age of Conifers, and colloquially as the Age of the Dinosaurs is the second-to-last era of Earth's geological history, lasting from about , comprising the Triassic, Jurassic and Cretace ...

and older rocks and floored with

tertiary Tertiary ( ) is a widely used but obsolete term for the geologic period from 66 million to 2.6 million years ago. The period began with the demise of the non-avian dinosaurs in the Cretaceous–Paleogene extinction event, at the start ...

lake beds and recent

alluvium Alluvium (from Latin ''alluvius'', from ''alluere'' 'to wash against') is loose clay, silt, sand, or gravel that has been deposited by running water in a stream bed, on a floodplain, in an alluvial fan or beach, or in similar settings. ...

. Physiographic evidences indicate that the Clarkston Valley is a structural depression on the east by a fault of post-

Miocene The Miocene ( ) is the first epoch (geology), 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 mea ...

age. Presumably the origin of the earthquake was on this fault at a considerable depth below the surface. In the neighborhood of Deer Lodge several faults of apparently small extent that trend northwestward are mapped by the geologists of the Anaconda Copper Mining. Their age and displacement are not known. In the hills west of Missouri River is an

overthrust 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 ...

fault, called the Lombard overthrust, that extends from a point north of Three Forks northeastward for 13 miles. Its trace crosses Horseshoe Bend about a mile west of Lombard.

Earthquake

The earthquake struck at evening in Montana local time with the epicenter being located right near

. The earthquake had an intensity of IX ''(Violent)'', and was felt in

Oregon Oregon () is a state in the Pacific Northwest region of the Western United States. The Columbia River delineates much of Oregon's northern boundary with Washington, while the Snake River delineates much of its eastern boundary with Idaho. T ...

Idaho Idaho ( ) is a state in the Pacific Northwest region of the Western United States. To the north, it shares a small portion of the Canada–United States border with the province of British Columbia. It borders the states of Montana and Wyomi ...

Wyoming Wyoming () is a state in the Mountain West subregion of the Western United States. It is bordered by Montana to the north and northwest, South Dakota and Nebraska to the east, Idaho to the west, Utah to the southwest, and Colorado to the s ...

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 ...

in the United States and

British Columbia British Columbia (commonly abbreviated as BC) is the westernmost province of Canada, situated between the Pacific Ocean and the Rocky Mountains. It has a diverse geography, with rugged landscapes that include rocky coastlines, sandy beaches, ...

, Saskatchewan,

Alberta Alberta ( ) is one of the thirteen provinces and territories of Canada. It is part of Western Canada and is one of the three prairie provinces. Alberta is bordered by British Columbia to the west, Saskatchewan to the east, the Northwest Ter ...

in Canada. Despite the intensity, there were no deaths since back then the area was sparsely populated and the property damage didn't exceed US$ 150,000.

Impact

A school in

Manhattan Manhattan (), known regionally as the City, is the most densely populated and geographically smallest of the five boroughs of New York City. The borough is also coextensive with New York County, one of the original counties of the U.S. state ...

was damaged beyond repair as well as other schools in Willow Creek, Bozeman and Radersburg being seriously damaged, along with many brick, stone and cement buildings including a church at Three Forks, Logan and a court house in White Sulphur Springs. Many buildings were damaged, pavements were cracked, windows were broken and chimneys toppled as a result of the earthquake. The shaking triggered landslides along the Missouri River which blocked railroad traffic for several weeks.

Casualties

Even though there were no deaths from the earthquake, at least two people were injured including a woman who broke her leg while rushing out of her home.

References

External links

* {{Earthquakes in the United States 1925 earthquakes Earthquakes in the United States Natural disasters in Montana 1925 natural disasters in the United States Montana earthquake