The Laramide orogeny was a period of mountain building in western North America, which started in the Late Cretaceous, 70 to 80 million years ago, and ended 35 to 55 million years ago. The exact duration and ages of beginning and end of the orogeny are in dispute, as is the cause. The Laramide orogeny occurred in a series of pulses, with quiescent phases intervening. The major feature that was created by this orogeny was the Rocky Mountains, but evidence of this orogeny can be found from Alaska to northern Mexico, with the easternmost extent of the mountain-building represented by the Black Hills of South Dakota. The phenomenon is named for the Laramie Mountains of eastern Wyoming. Mountain building is when mountains develop out of previously lower terrain, or even seas. ... World map showing North America A satellite composite image of North America. ... The Cretaceous period is one of the major divisions of the geologic timescale, reaching from the end of the Jurassic period, about 146 million years ago (Ma), to the beginning of the Paleocene epoch of the Tertiary period (65. ... Orogeny is the process of mountain building, and as such is both a tectonic structural event, a geographical event and a chronological event, in that orogenic events happen within a time frame, affect certain regions of rocks and crust, and cause distinctive structural phenomena and related tectonic activity. ... White Goat Wilderness Area, Alberta, Canada View of the Rocky Mountains as depicted on the Colorado state quarter The Rocky Mountains, often called the Rockies, are a broad mountain range in western North America. ... Official language(s) English Capital Juneau Largest city Anchorage Area  Ranked 1st  - Total 663,267 sq mi (1,717,854 km²)  - Width 808 miles (1,300 km)  - Length 1,479 miles (2,380 km)  - % water 13. ... This article is about the place in South Dakota. ... Official language(s) English Capital Pierre Largest city Sioux Falls Area  Ranked 17th  - Total 77,163 sq mi (199,905 km²)  - Width 210 miles (340 km)  - Length 380 miles (610 km)  - % water 1. ... The Laramie Mountains are shown highlighted on a map of the western United States The Laramie Mountains are a range of moderately high peaks on the eastern edge of the Rocky Mountains in the state of Wyoming in the United States. ... Official language(s) English Capital Cheyenne Largest city Cheyenne Area  Ranked 11th  - Total 97,818 sq mi (253,348 km²)  - Width 280 miles (450 km)  - Length 360 miles (580 km)  - % water 0. ...

The orogeny is commonly attributed to events off the west coast of North America, where the Farallon Plate was sliding under the North American plate. Most hypotheses propose that the angle of subduction became shallow, and as a consequence, no magmatism occurred in the central west of the continent, and the underlying oceanic lithosphere actually caused drag on the root of the overlying continental lithosphere. One cause for shallow subduction may have been an increased rate of plate convergence. Another proposed cause was subduction of thickened oceanic crust. The Farallon Plate is an ancient tectonic plate which began subducting as Pangaea broke apart during the Jurassic period. ... The North American plate is shown in brown on this map The North American Plate is a continental tectonic plate covering most of North America, extending eastward to the Mid-Atlantic Ridge and westward to the Cherskiy Range in East Siberia. ... Subduction zones mark sites of convective downwelling of the Earths lithosphere. ... The tectonic plates of the Lithosphere on Earth. ...

Magmatism associated with subduction occurred not near the plate edges (as in the volcanic arc of the Andes, for example), but far to the east. Geologists call such a lack of volcanic activity near a subduction zone a magmatic null. This particular null may have occurred because the subducted slab was in contact with relatively cool continental lithosphere, not hotter asthenosphere. One result of shallow angle of subduction and the drag that it caused was a broad belt of mountains, some of which were the progenitors of the Rocky Mountains. A volcanic arc is a chain of volcanic islands or mountains located near the edge of continents that are formed as the result of tectonic plate subduction. ... The Andes between Chile and Argentina The Andes form the longest mountain chain in the world. ... Categories: Geology stubs | Plate tectonics ...

Part of the proto-Rocky Mountains would be later modified by extension to become the Basin and Range Province. Basin and Range index map - USGS The Basin and Range Province is a particular type of topography that covers much of the southwestern United States and northwestern Mexico that is typified by elongate north-south trending arid valleys bounded by mountain ranges which also bound adjacent valleys. ...

Compare the earlier Sevier orogeny and the still-earlier Nevadan orogeny of the late Jurassic — early Cretaceous. The Sevier orogeny was a mountain-building event that affected western North America between aproximately 140 million years ago (Ma), and 50 Ma. ... The Nevadan Orogeny was a major mountain building event that took place along the western edge of ancient North America between the Mid to Late Jurassic(between about 180 and 146 million years ago). ... The Jurassic period is a major unit of the geologic timescale that extends from about 200 Ma (million years ago) at the end of the Triassic to 146 Ma at the beginning of the Cretaceous. ... The Cretaceous period is one of the major divisions of the geologic timescale, reaching from the end of the Jurassic period, about 146 million years ago (Ma), to the beginning of the Paleocene epoch of the Tertiary period (65. ...

References

• Joseph M. English and Stephen T. Johnston, The Laramide Orogeny: What Were the Driving Forces? International Geology Review 46, p. 833-838, 2004.

• Jason Saleeby, Segmentation of the Laramide Slab -- Evidence from the southern Sierra Nevada region. Geological Society of America Bulletin 115, p. 655-668, 2003.

External links

• Maps, animation, detailed information (UCLA)
• Laramide orogeny