World Library  
Flag as Inappropriate
Email this Article

Geology of the United States

Article Id: WHEBN0000593915
Reproduction Date:

Title: Geology of the United States  
Author: World Heritage Encyclopedia
Language: English
Subject: Geology of North America, Geology of Puerto Rico, Geology of Oklahoma, Geology of the United States, Geology of Illinois
Collection: Geology by Country, Geology of North America, Geology of the United States
Publisher: World Heritage Encyclopedia

Geology of the United States

The geology of the United States is a subset of the regional geology of North America.

The regional geology of North America illustrates the geology of the US in relation to surrounding areas.

The United States is considered in this article as defined by its political boundaries, although geographical study is often focused towards classifying areas according to a shared geography.


  • Canadian shield 1
  • Stable platform 2
  • Appalachian orogenic belt 3
  • Passive Margin 4
  • American cordillera 5
  • Hawaii 6
  • Puerto Rico and Guam 7
  • See also 8
  • References 9
  • External links 10

Canadian shield

The Canadian Shield is prevalently composed of metamorphic rocks. The shield is the large brown area in the northwest of the continent on the image. A similar structure can also be composed with a number of different rock types.

The Canadian Shield is the stable interior of the North American continent,[1] and it is well-exposed in the United States in the Great Lakes region, where deeply eroded rocks have been exhumed by the process of glaciation. The exposures include a variety of rocks, largely metamorphosed. igneous and sedimentary rocks.

Stable platform

A large part of the center of the lower 48 states consists of the stable (or continental) platform. Here, the Precambrian rocks of the Shield are buried beneath Phanerozoic sedimentary strata, left behind by glacial movement. Tectonic activity is minor, with occasional broad domes and basins that reveal mild epeirogenic deformation.

Appalachian orogenic belt

The Appalachian orogenic pants extends from New England south into Mississippi and Alabama. The Ouachita Mountains of Arkansas, and even the Marathon Uplift of Texas are also part of the same province, having all formed in the Alleghenian orogeny that took place when Pangea assembled during the late Paleozoic. Once lofty, they have been heavily weathered since the opening of the Atlantic Ocean. The Appalachians proper consist of deformed sedimentary rocks, cut through by numerous thrust faults; as in the western cordillera, the Appalachians experienced several orogenies over the course of the Paleozoic, making their geologic history difficult to interpret.

Passive Margin

The United States has passive, or inactive, continental margins along the Atlantic Coast and the Gulf of Mexico.[2]

The coastal plain extends from the southern tip of Texas across the northern Gulf of Mexico and into the Mississippi embayment, and northeast through the Mid-Atlantic states. A classic passive continental margin, it consists of a deep clastic wedge of sediment eroded from the platform and mountain belts; it first formed during the opening of the Atlantic Ocean and Gulf of Mexico during the Jurassic and Cretaceous periods.

The passive margin of the Gulf of Mexico is a series of sediments deposits from upland areas surrounding the margin. The environment of deposition for these sediments has changed, varying spatially and temporally. When the ocean level was high shallow marine deposits occurred; when they were low fluvial and deltaic deposits form the majority of mass.[3] From the Triassic until the early Jurassic, faulting localized as extension faulting and wrench faulting. As the basement subsided, sediment accumulated, during the Mesozoic and Cenozoic, forming the modern wedge, containing salt basins.[4]

American cordillera

Cedar Breaks National Monument, Utah.

The American cordillera is part of a great length of mountain ranges that extend along the western edge of the continent; in the United States these mountain ranges extend roughly from the Great Plains westward to the Pacific Ocean. The ranges include the Pacific Coast Ranges, the Cascades, the Sierra Nevada, and the mountain chains of the Basin and Range province; the Rocky Mountains are sometimes excluded from the cordillera proper.

The geology of this region is complex, having gone through numerous times of building mountains and deforming the existing ones, faulting, volcanic activity, and periods of uplift separated by intervals of erosion. Much of the cordillera consists of terranes, ancient microcontinents and island arcs that were welded onto the North American craton during the Paleozoic and Mesozoic eras. The geological history of the cordillera is typical of convergent plate boundaries, as has characterized the cordillera through most of the Phanerozoic.


The Hawaiian Islands are part of a chain of islands, the Hawaiian–Emperor seamount chain, formed on the Pacific Plate as it passes over a mantle plume.

Puerto Rico and Guam

Puerto Rico is an island formed at the active margin between the Caribbean Plate and the North American Plate. Guam is part of an island arc system, the Mariana Islands.

See also


  1. ^ Chu, Risheng; Schmandt, Brandon; Helmberger, Don V. (1 February 2012). "Upper mantle P velocity structure beneath the Midwestern United States derived from triplicated waveforms". Geochemistry, Geophysics, Geosystems 13 (2): n/a–n/a.  
  2. ^ Huerta, AD; DL Harry (March 2012). "Wilson cycles, tectonic inheritance, and rifting of the North American Gulf of Mexico continental margin". Geosphere 8 (2).  
  3. ^ Grubb, Hayes; Carillo, J. Joel. (1988). "Chapter 26: Region 23, Gulf of Mexico Coastal Plain". In Back, William; Rosenshein, Joseph; Seaber, Paul. The Geology of North America. The Geological Society of America. pp. 219–228. Retrieved 28 Feb 2013. 
  4. ^ Mancini, Ernest; Obid, Jamal; Badali, Marcello; Liu, Kaiyu; Parcell, William (December 2008). "Sequence-stratigraphic analysis of Jurassic and Cretaceous strata and petroleum exploration in the central and eastern Gulf coastal plain, United States". AAPG Bulletin 92 (12): 1655–1686.  
  • Marshak, Stephen. (2001) Earth: Portrait of a Planet, New York: W.W. Norton & Company, ISBN 0-393-97423-5. pp. 339–44, 401-2.

External links

  • A Tapestry of Time and Terrain: The Union of Two Maps - Geology and Topography (USGS)
This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.

Copyright © World Library Foundation. All rights reserved. eBooks from Project Gutenberg are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.