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Lifted fault-block geology Tilted fault-block formation in the Teton Range. Fault-block mountains often result from rifting, an indicator of extensional tectonics. These can be small or form extensive rift valley systems, such as the East African Rift zone. Death Valley in California is a smaller example.
The Rwenzori Mountains in the East African Rift are an upthrown fault block, and are the highest non-volcanic, non-orogenic mountains in the world. [13] [14] The Vosges Mountains in France were formed by isostatic uplift in response to the opening of the Rhine Graben, a major extensional basin. [15]
The west block along the fault line rose to form the Teton Range, creating the youngest mountain range in the Rocky Mountains. The fault's east block fell to form the valley called Jackson Hole . The geological processes that led to the current composition of the oldest rocks in the Teton Range began about 2.5 billion years ago.
When a fault block is raised or tilted, a block mountain can result. [17] Higher blocks are called horsts, and troughs are called grabens. A spreading apart of the surface causes tensional forces. When the tensional forces are strong enough to cause a plate to split apart, it does so such that a center block drops down relative to its flanking ...
The Basin and Range Province in the western United States is an extensive region of alternating valleys and ridges caused by horst and graben as well as tilted block faulting. [ 1 ] The Condroz and Ardennes regions of Wallonia are good examples of a succession of horst and graben.
Sleeping Giant, a fault-block ridge that formed 200 million years ago during the Triassic and Jurassic periods, is composed of traprock, also known as basalt, an extrusive volcanic rock. Minor earthquakes have also been measured by seismographs and reported by residents.
Steens Mountain is a large fault-block mountain in the northwest United States, located in Harney County, Oregon. [2] [3] Stretching some fifty miles (80 km) north to south, on its west side it rises from the Alvord Desert at an elevation of about 4,200 feet (1,280 m) to 9,738 feet (2,968 m) at the summit.
Representation of the Teton fault block. Uplift and erosion of the footwall has resulted in the Teton Range. The Teton fault is a normal fault. Therefore, movement on the fault is primarily in a vertical direction. Movement on the Teton fault occurs on a plane that averages a strike of N10°E and dips 45° to 75° to the east. [1]