The Teton fault is a

normal fault In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectonic ...

located in northwestern

Wyoming Wyoming () is a U.S. state, state in the Mountain states, 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 south ...

. The fault has a length of 44 miles (70 km) and runs along the eastern base of the

Teton Range The Teton Range is a mountain range of the Rocky Mountains in North America. It extends for approximately in a north–south direction through the U.S. state of Wyoming, east of the Idaho state line. It is south of Yellowstone National Park and ...

. Vertical movement on the fault has caused the dramatic topography of the Teton Range.Byrd, J.O.D., Smith, R.B., Geissman, J.W. (1994) The Teton fault, Wyoming: Topographic signature, neotectonics, and mechanisms of deformation. ''Journal of Geophysical Research (99)''. No. B10. p. 20095–20122.Pickering-White, B.J., Smith, R.B., Husen, S., Farrell, J.M., Wong, I. (2009). Seismicity and earthquake hazard analysis of the Teton-Yellowstone region, Wyoming. ''Journal of Volcanology and Geothermal Research. (188)'' p. 277–296

Geologic setting

The Teton fault is located in a unique geologic setting. The fault is on the boundary of four major

geologic province A geologic province is a spatial entity with common geologic attributes. A province may include a single dominant structural element such as a basin or a fold belt, or a number of contiguous related elements. Adjoining provinces may be simila ...

s: the Basin and Range, Idaho-Wyoming Thrust belt, Rocky Mountain Foreland, and the Yellowstone volcanic plateau. The

Basin and Range province The Basin and Range Province is a vast physiographic region covering much of the inland Western United States and northwestern Mexico. It is defined by unique basin and range topography, characterized by abrupt changes in elevation, alternating ...

is a region of east-west crustal extension. This province adds tension perpendicular to the fault line causing the fault blocks to move apart. The Idaho-Wyoming Thrust belt is located south of the Teton fault and is a region of thick and deformed crust that prevents the fault from extending farther south. The Rocky Mountain Foreland is located east of the Teton fault and is a region of thicker crust. This section of crust is heavier and adds to the vertical downward force on the

hanging wall In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectonic ...

of fault. The

Yellowstone Yellowstone National Park is an American national park located in the western United States, largely in the northwest corner of Wyoming and extending into Montana and Idaho. It was established by the 42nd U.S. Congress with the Yellowston ...

volcanic plateau is a region of uplift and expansion that influences both vertical and horizontal forces on the Teton fault. The Teton fault is unique in that it dips or slopes to the east. The majority of major faults in the Basin and Range province dip to the west. The unique dip of the Teton fault can be explained by the subsidence of the

Snake River Plain image:Snake River view near Twin Falls, Idaho.jpg, The Snake River cutting through the plain leaves many canyons and Canyon#List of gorges, gorges, such as this one near Twin Falls, Idaho The Snake River Plain is a geology, geologic feature ...

. The Snake River Plain is located to the west of the Teton fault and was formed by the migration of the

Yellowstone hotspot The Yellowstone hotspot is a volcanic hotspot in the United States responsible for large scale volcanism in Idaho, Montana, Nevada, Oregon, and Wyoming, formed as the North American tectonic plate moved over it. It formed the eastern Snake Ri ...

forming prehistoric calderas across southern Idaho. As this section of crust cools it tends to subside causing the

footwall In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectonic ...

of the fault to tilt down toward the west. The Teton fault is also an important feature in a larger region of seismic activity called the Intermountain Seismic Belt. This region extends from western Montana south to northern Arizona.Smith, R.B., Byrd, O.D., (1993). The Teton fault, Wyoming: seismotectonics, Quaternary history, and earthquake hazards. ''Geology of Wyoming: Geological Survey of Wyoming Memoir.'' No. 5, p. 628–667.

Geologic history

The development of the Teton fault has been influenced by many past geologic events. In 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 ...

, extensive

plutonism Plutonism is the geologic theory that the igneous rocks forming the Earth originated from intrusive magmatic activity, with a continuing gradual process of weathering and erosion wearing away rocks, which were then deposited on the sea bed, re- ...

caused

metamorphism Metamorphism is the transformation of existing rock (the protolith) to rock with a different mineral composition or texture. Metamorphism takes place at temperatures in excess of , and often also at elevated pressure or in the presence of chem ...

and deformation of the region that would become the Teton Range. During the

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 Cretaceo ...

and early

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 ...

, the region underwent compression and crustal thickening. This formed

thrust faults 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 ...

and folds. In the Late Tertiary, compressional forces ceased and extensional forces began. This led to the development of the Basin and Range province beginning 20–17 million years ago. The age of the Teton fault is somewhat controversial. Most estimates range between 2 and 13 million years old with a consensus that most of the movement on the fault occurred within the last 2 million years. Rates of movement on the fault have changed throughout time. At the end of the Pinedale glaciation 16,000 to 14,000 years ago, slip on the fault increased. This was likely due to changing stresses on the fault as glaciers melted.Hampel, A., Hetzel, R., Densmore, A.L. (2007). Postglacial slip-rate increase on the Teton normal fault, northern Basin and Range Province, caused by melting of the Yellowstone ice cap and deglaciation for the Teton Range? ''The Geological Society of America. (35)''. No. 12. p. 1107–1110. The largest known earthquakes on the fault in recent history occurred around 4800 and 8000 years ago. The long intervals between large earthquakes on the fault are consistent with other normal faults in the Intermountain Seismic Belt.

Fault movement

The Teton fault is a

. Therefore, movement on the fault is primarily in a vertical direction. Movement on the Teton fault occurs on a plane that averages a

strike Strike may refer to: People * Strike (surname) Physical confrontation or removal *Strike (attack), attack with an inanimate object or a part of the human body intended to cause harm *Airstrike, military strike by air forces on either a suspected ...

of N10°E and dips 45° to 75° to the east. The 44 mile length of the fault is broken into three segments. These segments may move separately or with other segments. The southern segment extends from the town of

Wilson, Wyoming Wilson is a census-designated place (CDP) in Teton County, Wyoming, United States. The population was 1,567 at the 2020 census, up from 1,482 in 2010. It is part of the Jackson, WY– ID Micropolitan Statistical Area. Wilson was pioneered ...

north to

Taggart Lake Taggart Lake is located in Grand Teton National Park, in the U. S. state of Wyoming. The natural lake is located at the terminus of Avalanche Canyon. A number of hiking trails can be found near the lake including a roundtrip hike commencing from ...

. The middle segment extends from Taggart Lake to the south end of Jackson Lake. The northern segment extends to the north end of Jackson Lake. The Teton fault is somewhat unusual in the amount of movement that has occurred over a relatively short amount of time. The amount of movement on the fault over its lifetime has been estimated to range from about 20,000 to 30,000 feet (6–9 km). Some evidence suggests total displacement on the fault may be as high as 36,000 feet (11 km). The average rate of movement on the fault for the late

Quaternary The Quaternary ( ) is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS). It follows the Neogene Period and spans from 2.58 million years ...

is about 1.3 millimeters per year.

Earthquake hazard

The earthquake hazard in the Teton-Yellowstone region is the highest in the intermountain west. Large earthquakes of magnitude 6.5 to 7.0 are estimated to occur in this region roughly every 200 years. However, the Teton fault contributes very little in the way of seismic activity as large earthquakes on the fault occur every 1600 to 6000 years. Most large earthquakes in the region are associated with the Yellowstone caldera and other faults in the area. In a study conducted from 1986 to 2002, it was found that the Teton fault had very little seismic activity. Despite its lack of recent seismic activity, it is believed that the Teton fault could produce a 7.5 magnitude earthquake. An earthquake this large would cause severe ground shaking and potential

liquefaction In materials science, liquefaction is a process that generates a liquid from a solid or a gas or that generates a non-liquid phase which behaves in accordance with fluid dynamics. It occurs both naturally and artificially. As an example of the ...

in the valley of Jackson Hole. This would damage or destroy infrastructure and buildings not built to seismic standards. An earthquake could cause the valley of Jackson Hole to tilt slightly to the west altering stream and river channels as well as changing groundwater levels. This could cause flooding in some low-lying areas. A large earthquake would also have the potential to trigger other hazards such as landslides, rockslides and avalanches.

References

External links

* http://www.uusatrg.utah.edu/teton.html {{Faults Geology of Wyoming Seismic faults of the United States