lithosphere
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| lithosphere | |
|---|---|
| Name | Lithosphere |
| Type | Geological layer |
| Composition | Earth's crust, mantle lithologies |
| Thickness | variable |
| Discovery | Alfred Wegener (continental drift concept), Harry Hess (seafloor spreading) |
lithosphere The lithosphere is the rigid outer shell of Earth that includes the crust and the uppermost solid mantle. It interacts with major geological agents such as Mid-Atlantic Ridge, Ring of Fire, Himalaya, San Andreas Fault and influences phenomena observed by James Hutton, Charles Lyell, Marie Tharp, Vine–Matthews–Morley hypothesis researchers. Studies by institutions like the United States Geological Survey, Scripps Institution of Oceanography, Geological Survey of Canada, British Geological Survey and projects including International Seismological Centre integrate seismology, petrology and geodesy.
Definition and Composition
The lithosphere is defined in geoscience literature by boundary criteria used by Andrija Mohorovičić, Inge Lehmann, Robert Hess, Norman Bowen and the Geophysical Journal International community, combining petrological, seismic and rheological definitions. Its composition ranges from felsic crustal rocks typified by exposures such as the Canadian Shield, Scandinavian Shield, Baltic Shield and Guiana Shield to mafic oceanic sequences found at the East Pacific Rise and Mid-Atlantic Ridge. Major rock types include granitic suites studied at Sierra Nevada, basaltic plateaus like the Columbia River Basalt Group, ophiolites exemplified by the Semail Ophiolite and metamorphic terranes in the Himalayan orogeny, often catalogued by institutions such as the Smithsonian Institution.
Structure and Mechanical Properties
The lithosphere exhibits layered architecture analyzed with methods from Global Positioning System, InSAR, seismology, magnetotellurics and petrophysics. Mechanical behavior is governed by elastic, brittle and ductile regimes referenced in works by Anderson (geophysicist), Gutenberg, Reid (geophysicist), and datasets from Incorporated Research Institutions for Seismology. Local thickness varies from thin plates beneath the East Pacific Rise to thick cratonic roots such as Kaapvaal Craton, Pilbara craton and Yilgarn Craton, with effective elastic thickness discussed in publications from Royal Society journals and Nature Geoscience.
Formation and Geological Evolution
Lithospheric formation and evolution are interpreted through frameworks developed by Alfred Wegener, expanded by Arthur Holmes radioactive heat transport theories and refined by John Tuzo Wilson plate circuit reconstructions. Processes include accretion at convergent margins like the Andes and Alps, rifting events such as the East African Rift, terrane amalgamation recorded in the Appalachian Mountains and magmatic underplating documented at Iceland and Deccan Traps. Geological evolution is constrained by radiometric methods developed by Willard Libby, stratigraphic schemes of William Smith (geologist), and palaeomagnetic studies from laboratories at University of Cambridge, California Institute of Technology and ETH Zurich.
Plate Tectonics and Lithospheric Plates
Lithospheric plates are central to the plate tectonics paradigm codified by Harry Hess, W. Jason Morgan, Dan McKenzie and formalized by compilations from USGS and NOAA. Major plates—Pacific Plate, Eurasian Plate, African Plate, North American Plate, South American Plate, Antarctic Plate and Indian Plate—interact at boundaries such as the San Andreas Fault, East Pacific Rise, Juan de Fuca Plate, Nazca Plate subduction beneath the Peru-Chile Trench and collision zones like the Alpine orogeny. Plate motion reconstructions use data from GPS, paleogeography studies by Scotese, and numerical models from centers like Lamont–Doherty Earth Observatory.
Interactions with the Asthenosphere and Mantle
Coupling between the lithosphere and the underlying asthenosphere is investigated in work by Don L. Anderson and through seismic tomography by groups at IRIS, GFZ German Research Centre for Geosciences and IPGP. Processes include mantle convection proposed by Arthur Holmes, lithosphere delamination observed in Andean settings, plume-lithosphere interactions at Hawaii and Iceland, and slab rollback illustrated by Ring of Fire dynamics. Heat flow datasets from International Heat Flow Commission and geochemical signals traced to Mid-Ocean Ridge Basalt sources help delineate lithosphere-asthenosphere exchange.
Types: Oceanic vs Continental Lithosphere
Oceanic lithosphere, exemplified by the Nazca Plate and segments of the Pacific Plate, is thinner, denser and basaltic as seen at Mid-Atlantic Ridge and East Pacific Rise, forming predictable age-thickness profiles validated by the Vine–Matthews–Morley hypothesis and studies at Lamont–Doherty. Continental lithosphere—represented by Laurentia, Gondwana fragments and shields like the Canadian Shield—is thicker, compositionally heterogeneous and hosts cratons such as Slave Craton, Superior Craton and Kalahari Craton, with complex rheology explored in papers from Geological Society of America.
Role in Surface Processes and Resources
The lithosphere underpins orogenic processes that build ranges such as the Rocky Mountains, controls sedimentary basins including the Permian Basin and Gulf of Mexico, and localizes mineralization in districts like the Carlin Trend, Sudbury Basin and Bushveld Complex. It hosts hydrocarbon systems exploited by companies like ExxonMobil and Royal Dutch Shell, contains critical mineral deposits mined by BHP and Rio Tinto, and influences geothermal resources developed in regions like Iceland and Nevada. Hazards associated with lithospheric processes are monitored by agencies including USGS, Petroleum Engineering departments and international consortia such as Global Earthquake Model.