Geologic provinces of the world (USGS)

Shield      Platform      Orogen      Basin      Large igneous province      Extended crust

Oceanic crust:      0–20 Ma      20–65 Ma      >65 Ma

In geology, a crust is the outermost solid shell of a planet or moon. A geologic or geomorphic province is a spatial entity with common geologic / geomorphic attributes The United States Geological Survey ( USGS) is a scientific agency of the United States government. A shield is generally a large area of exposed Precambrian Crystalline igneous and high-grade metamorphic rocks that form tectonically In geology a platform is a continental area covered by relatively flat or gently tilted mainly Sedimentary strata, which overlie a basement of consolidated Orogeny (Greek for "mountain generating" is the process of natural Mountain building and may be studied as a tectonic structural event as a geographical event and A structural basin is a large-scale structural formation of rock strata formed by tectonic warping of previously flat lying strata. Large Igneous provinces (LIPS were originally defined by Coffin and Eldholm (1992 as areas of Earth's surface that contain very large volumes of magmatic rocks (typically Oceanic crust is the part of Earth's Lithosphere that surfaces in the Ocean basins Annum is one form of the Latin noun meaning Year, not a form normally used for derivatives in modern languages the accusative singular Geology (from Greek γη gê, "earth" and λόγος Logos, "speech" lit Crust is chemically and mechanically different from underlying material. Crusts of Earth, our Moon, Mercury, Venus, and Mars have been generated largely by igneous processes, and these crusts are richer in incompatible elements than the underlying mantles. The VENUS ( V ictoria E xperimental N etwork U nder the S ea project is a cabled sea floor observatory operated by the University Igneous rocks (etymology from Latin ignis, fire are rocks formed by solidification of cooled Magma (molten rock Incompatible element is a term used in Petrology and Geochemistry. The mantle is a part of an Astronomical object. The interior of the Earth, similar to the other Terrestrial planets, is Chemically divided Crusts are also present on moons of outer planets and have formed by similar or analogous processes: for instance, Io, a moon of Jupiter, also has a crust formed by igneous processes. TemplateInfobox Planet.--> Io (ˈaɪoʊ, or as Greek

Earth has the best characterized and perhaps the most complex crust of all the planets and moons in our solar system. The Solar System consists of the Sun and those celestial objects bound to it by Gravity. An overview of our crust is provided in the entry on Structure of the Earth, and the two contrasting types of crust are discussed in entries on continental crust and oceanic crust. The interior of Earth, similar to the other Terrestrial planets, is Chemically divided into layers The continental crust is the layer of granitic, Sedimentary, and Metamorphic rocks which form the Continents and the areas of shallow seabed Oceanic crust is the part of Earth's Lithosphere that surfaces in the Ocean basins Despite the details known about Earth's crust, its early history is obscure. The rapidly growing base of knowledge about other bodies in the solar system provides insights into the beginnings of Earth history as well as into other possible paths of planetary evolution. Studies of the Moon have been particularly valuable for understanding the early Earth.

Perspective from the Moon

The Moon provides an unusual opportunity to study how crust can first form, for at least these two reasons. First, ancient crust is well-preserved because the Moon has never had plate tectonics or an atmosphere or surface water. Second, there are many extremely well-characterized samples of the crust from known locations.

The limited summary below is intended for comparative purposes, and much of the content is based on the overview of Hiesinger and Head (2006) ^[1] and other papers in the same volume. Much more information can be found in the complementary entries about the Geology of the Moon and the Moon. The geology of the Moon (sometimes called selenology, although the latter term can refer more generally to "lunar

Most of the crust of the moon crystallized from magma formed as a consequence of intense meteorite bombardment in the early history of our solar system. A particularly large meteorite is thought to have collided with the forming Earth, and part of the material ejected into space by the collision accreted to form the Moon. As the Moon formed, the outer part of it is thought to have been molten, a “lunar magma ocean. According to the Giant impact hypothesis a large amount of energy was liberated in the formation of the Moon and it is predicted that as a result a large portion of the Moon was once completely ” Plagioclase feldspar crystallized in large amounts from this magma ocean and floated towards the surface. Plagioclase is a very important series of tectosilicate Minerals within the Feldspar family Feldspar is the name of a group of rock-forming Minerals which make up as much as 60% of the Earth 's crust. Magma (Plurals magmas and magmata) is molten rock that sometimes forms beneath the surface of the Earth (or any other Terrestrial planet The cumulate rocks form much of the crust. Cumulate rocks are Igneous rocks formed by the accumulation of Crystals from a Magma either by settling or floating The upper part of the crust probably averages about 88% plagioclase (near the lower limit of 90% defined for anorthosite): the lower part of the crust may contain a higher percent of ferromagnesian minerals such as the pyroxenes and olivine, but even that lower part probably averages about 78% plagioclase. Anorthosite (æˈnɔrθəsaɪt/ /ə- is a Phaneritic, Intrusive Igneous rock characterized by a predominance of Plagioclase Feldspar The pyroxenes are a group of important rock-forming Silicate minerals found in many Igneous and metamorphic rocks. The Mineral olivine (when gem-quality also called Peridot) is a Magnesium Iron silicate with the formula ( Mg ^[2] The underlying mantle is denser and olivine-rich.

The thickness of the crust ranges between about 20 and 120 km. Crust on the far side of the moon averages about 12 km thicker than that on the near side. Estimates of average thickness fall in the range from about 50 to 60 km. Most of this plagioclase-rich crust formed shortly after formation of the moon, between about 4. 5 and 4. 3 billion years ago. Perhaps 10% or less of the crust consists of igneous rock added after formation of the initial plagioclase-rich material. The best-characterized and most voluminous of these later additions are the mare basalts formed between about 3. Basalt (bəˈsɔːlt ˈbeisɔːlt ˈbæsɔːlt is a common Extrusive Volcanic rock. 9 and 3. 2 billion years ago. Minor volcanism continued after 3. 2 billion years, perhaps as recently as 1 billion years ago. There is no evidence of crustal formation or deformation due to plate tectonics. Plate tectonics (from Greek τέκτων tektōn "builder" or "mason" describes the large scale motions of Earth 's Lithosphere

Study of the Moon has established that a crust can form on a rocky planetary body significantly smaller than Earth. Although the radius of the Moon is only about a quarter that of Earth, the lunar crust has a significantly greater average thickness. This relatively thick crust formed almost immediately after formation of the Moon. Magmatism continued after the period of intense meteorite impacts ended about 3. Igneous rocks (etymology from Latin ignis, fire are rocks formed by solidification of cooled Magma (molten rock 9 billion years ago, but igneous rocks younger than 3. Igneous rocks (etymology from Latin ignis, fire are rocks formed by solidification of cooled Magma (molten rock 9 billion years make up only a minor part of the crust.

Earth's crust

Earth cutaway from core to exosphere. EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001 The planetary core consists of the innermost layer(s of a Planet. The exosphere is the uppermost layer of the atmosphere. On Earth, its lower boundary at the edge of the Thermosphere is estimated to be 500 km to

The crust of the Earth is composed of a great variety of igneous, metamorphic, and sedimentary rocks. EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001 Igneous rocks (etymology from Latin ignis, fire are rocks formed by solidification of cooled Magma (molten rock Sedimentary rock is one of the three main rock types (the others being igneous and Metamorphic rock) The crust is underlain by the mantle. The mantle is a part of an Astronomical object. The interior of the Earth, similar to the other Terrestrial planets, is Chemically divided The upper part of the mantle is composed mostly of peridotite, a rock denser than rocks common in the overlying crust. A peridotite is a dense coarse-grained Igneous rock, consisting mostly of the minerals Olivine and Pyroxene. The boundary between the crust and mantle is conventionally placed at the Mohorovičić discontinuity, a boundary defined by a contrast in seismic velocity. The Mohorovičić discontinuity, usually referred to as the Moho, is the boundary between the Earth 's crust and the mantle. Seismology (from Greek grc σεισμός seismos, "earthquake" and grc -λογία -logia) is the scientific study of Earthquakes Earth's crust occupies less than 1% of Earth's volume.

The oceanic crust of the Earth is different from its continental crust. Oceanic crust is the part of Earth's Lithosphere that surfaces in the Ocean basins The continental crust is the layer of granitic, Sedimentary, and Metamorphic rocks which form the Continents and the areas of shallow seabed The oceanic crust is 5 km (3 mi) to 10 km (6 mi) thick^[3] and is composed primarily of basalt, diabase, and gabbro. Oceanic crust is the part of Earth's Lithosphere that surfaces in the Ocean basins Basalt (bəˈsɔːlt ˈbeisɔːlt ˈbæsɔːlt is a common Extrusive Volcanic rock. Diabase (ˈdaɪəbeɪs or Dolerite is a Mafic, Holocrystalline, Igneous rock equivalent to Volcanic Basalt or plutonic Gabbro (ˈɡæbrəʊ is a dark coarse-grained intrusive Igneous rock chemically equivalent to Basalt. The continental crust is typically from 30 km (20 mi) to 50 km (30 mi) thick, and it is mostly composed of less dense rocks than is the oceanic crust. The continental crust is the layer of granitic, Sedimentary, and Metamorphic rocks which form the Continents and the areas of shallow seabed Some of these less dense rocks, such as granite, are common in the continental crust but rare to absent in the oceanic crust. Granite (ˈɡrænɪt is a common and widely occurring type of intrusive, Felsic, igneous rock. The continental crust and the oceanic crust are sometimes called sial and sima respectively. Sial or SiAl is also the name for the upper layer of the Earth's crust, which is also known as the Continental crust because Due to the change in velocity of seismic waves it is believed that on continents at a certain depth sial becomes close in its physical properties to sima and the dividing line is called Conrad discontinuity. Seismic waves are Waves that travel through the Earth, most often as the result of a tectonic Earthquake, sometimes from an Explosion

The temperature of the crust increases with depth, reaching values typically in the range from about 500 °C (900 °F) to 1,000 °C (1,800 °F) at the boundary with the underlying mantle. The crust and underlying relatively rigid mantle make up the lithosphere. The lithosphere (IPA, from the Greek λίθος for "rocky" + σφαίρα for "sphere" is the solid outermost shell of a rocky Planet. Because of convection in the underlying plastic, although non-molten, upper mantle and asthenosphere, the lithosphere is broken into tectonic plates that move. Convection in the most general terms refers to the movement of molecules within Fluids (i In Materials science, deformation is a change in the shape or size of an object due to an applied force. The mantle is a part of an Astronomical object. The interior of the Earth, similar to the other Terrestrial planets, is Chemically divided The asthenosphere (from an invented Greek a + ' sthenos "without strength" and Greek word σφαίρα (sphera meaning globe is the Plate tectonics (from Greek τέκτων tektōn "builder" or "mason" describes the large scale motions of Earth 's Lithosphere

Partly by analogy to what is known about our Moon, Earth is considered to have differentiated from an aggregate of planetesimals into its core, mantle and crust within about 100 million years of the formation of the planet, 4. Planetesimals are solid objects thought to exist in Protoplanetary disks and in Debris disks A widely accepted theory of planet formation the so-called planetesimal The mantle is a part of an Astronomical object. The interior of the Earth, similar to the other Terrestrial planets, is Chemically divided 6 billion years ago. The primordial crust was very thin, and was likely recycled by much more vigorous plate tectonics and destroyed by significant asteroid impacts, which were much more common in the early stages of the solar system. Plate tectonics (from Greek τέκτων tektōn "builder" or "mason" describes the large scale motions of Earth 's Lithosphere Asteroids, sometimes called Minor planets or planetoids', are bodies—primarily of the inner Solar System —that are smaller than planets but

The Earth has likely always had some form of basaltic crust, but the age of the oldest oceanic crust today is only about 200 million years. In contrast, the bulk of the continental crust is much older. The oldest continental crustal rocks on Earth have ages in the range from about 3. 7 to 4. 0 billion years ^[4] and have been found in the Narryer Gneiss Terrane in Western Australia, in the Acasta Gneiss in the Northwest Territories on the Canadian Shield, and on other cratonic regions such as those on the Fennoscandian Shield. The Narryer Gneiss Terrane is a geological complex in Western Australia that is composed of a tectonically interleaved and polydeformed mixture of Granite, mafic Western Australia is a state occupying the entire western third of the Australian continent. The Acasta Gneiss is a rock Outcrop of Archaean Tonalite Gneiss in the Slave craton in Northwest Territories The Northwest Territories (ˌnɔrθˌwɛstˈtɛrɨtɔriz ( NWT or NT; French, les Territoires du Nord-Ouest) is a territory The Canadian Shield &mdash also called the Laurentian Plateau, or Bouclier Canadien (French &mdash is a large geological shield covered by The Baltic Shield (sometimes referred to as the Fennoscandian Shield) is located in Fennoscandia ( Norway, Sweden and Finland) northwest A few zircons with ages as great as 4. 3 billion years have been found in the Narryer Gneiss Terrane. The Narryer Gneiss Terrane is a geological complex in Western Australia that is composed of a tectonically interleaved and polydeformed mixture of Granite, mafic

The average age of the current Earth's continental crust has been estimated to be about 2. 0 billion years. ^[5] Most crustal rocks formed before 2. 5 billion years ago are located in cratons. A craton ( Greek kratos / κρἀτος ( neut. "strength" is an old and stable part of the Continental crust that has survived Such old continental crust and the underlying mantle lithosphere are less dense than elsewhere in the earth and so are not readily destroyed by subduction. The lithosphere (IPA, from the Greek λίθος for "rocky" + σφαίρα for "sphere" is the solid outermost shell of a rocky Planet. In Geology, a subduction zone is an area on Earth where two tectonic plates meet and move towards one another with one sliding underneath the other Formation of new continental crust is linked to periods of intense orogeny or mountain building; these periods coincide with the formation of the supercontinents such as Rodinia, Pangaea and Gondwana. Orogeny (Greek for "mountain generating" is the process of natural Mountain building and may be studied as a tectonic structural event as a geographical event and In Geology, a supercontinent is a Landmass comprising more than one Continental core or Craton. For the Genus of Metalmark butterflies, see Rodinia (butterfly. Pangaea, Pangæa or Pangea (pænˈdʒiːə from παν pan, meaning entire, and Γαῖα Gaea, meaning Earth in Gondwana (ɡɒnˈdwɑːnə originally Gondwanaland) was a southern Supercontinent that existed about 500 to 200 Ma ago The crust forms in part by aggregation of island arcs including granite and metamorphic fold belts, and it is preserved in part by depletion of the underlying mantle to form buoyant lithospheric mantle. A volcanic arc is a chain of volcanic islands or Mountains formed by Plate tectonics as an oceanic Tectonic plate subducts under Granite (ˈɡrænɪt is a common and widely occurring type of intrusive, Felsic, igneous rock. The mantle is a part of an Astronomical object. The interior of the Earth, similar to the other Terrestrial planets, is Chemically divided

Composition of the continental crust

The continental crust has an average composition similar to that of the igneous rock, andesite. Igneous rocks (etymology from Latin ignis, fire are rocks formed by solidification of cooled Magma (molten rock For the extinct cephalopod genus see Andesites. Andesite (ˈændəsaɪt is an igneous, Volcanic rock, of intermediate The composition tabulated below and the following discussion are based largely on the summary by Rudnick and Gao (2003). ^[6] Continental crust is enriched in incompatible elements compared to the basaltic ocean crust and much enriched compared to the underlying mantle. Incompatible element is a term used in Petrology and Geochemistry. Basalt (bəˈsɔːlt ˈbeisɔːlt ˈbæsɔːlt is a common Extrusive Volcanic rock. Although the continental crust comprises only about 0. 6 weight percent of the silicate Earth, it contains 20% to 70% of the incompatible elements.

Plates in the crust of the earth, according to the plate tectonics theory

All the other constituents except water occur only in very small quantities, and total less than 1%. Estimates of average density for the upper crust range between 2. 69 g/cm³ and 2. 74 g/cm³ and for lower crust between 3. 0 g/cm³ and 3. 25 g/cm^3[3].

References

1. ^ Herald Hiesinger and James W. Head III, 2006, New views of Lunar geoscience: An introduction and overview. Reviews in Mineralogy & Geochemistry 60, p. 1-81.
2. ^ Wieczorek, M. A. , and Zuber, M. T. , 2001, The composition and origin of the lunar crust: Constraints from central peaks and crustal thickness modeling. Geophysical Research Letters 28, p. 4023-4026.
3. ^ ^{a b} Structure and composition of the Earth. Australian Museum Online. Retrieved on 2007-09-14. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 81 - Domitian becomes Emperor of the Roman Empire upon the death of his brother Titus.
4. ^ P. J. Patchett and S. D. Samson, 2003, Ages and Growth ot the Continental Crust from Radiogenic Isotopes. In The Crust (ed. R. L. Rudnick) volume 3, pages 321-348 of Treatise on Geochemistry (eds. H. D. Holland and K. K. Turekian), Elsevier-Pergamon, Oxford
5. ^ A. I. S. Kemp and C. J. Hawkesworth, 2003, Granitic Perspectives on the Generation and Secular Evolution of the Contnental Crust. In The Crust (ed. R. L. Rudnick) volume 3, pages 349-410 of Treatise on Geochemistry (eds. H. D. Holland and K. K. Turekian), Elsevier-Pergamon, Oxford
6. ^ R. L. Rudnick and S. Gao, 2003, Composition of the Continental Crust. In The Crust (ed. R. L. Rudnick) volume 3, pages 1-64 of Treatise on Geochemistry (eds. H. D. Holland and K. K. Turekian), Elsevier-Pergamon, Oxford

External links

• USGS Crust Thickness Map