The crust of the Earth is composed of a great variety of igneous, metamorphic, and sedimentary rocks. The crust is underlain by the mantle. The upper part of the mantle is composed mostly of peridotite, a rock denser than rocks common in the overlying crust. Even more » Account Options. Sign in; Search settings. Data: 00:45:40 - 22/06/2013 De: noprescription E-mail: [email protected] Mensagem:comment5, ventolin ventolin, drug free bulletin board, 9327, cialis prix cialis prix. The boundary between the crust and mantle is conventionally placed at the Mohorovi? The crust occupies less than 1% of Earth's volume.[1]. The oceanic crust of the sheet is different from its continental crust. The oceanic crust is 5 km (3 mi) to 1. The continental crust is typically from 3. Some of these less dense rocks, such as granite, are common in the continental crust but rare to absent in the oceanic crust. No-registration upload of files up to 250MB. Not available in some countries. Partly by analogy to what is known about the Moon, Earth is considered to have differentiated from an aggregate of planetesimals into its core, mantle and crust within about 1. The primordial crust was very thin and was probably 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. Earth has probably always had some form of basaltic crust, but the age of the oldest oceanic crust today is only about 2. 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. 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. Some zircon with age as great as 4. Narryer Gneiss Terrane. A theoretical protoplanet named "Theia" 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.” Plagioclase feldspar crystallized in large amounts from this magma ocean and floated toward the surface. The cumulate rocks form much of the crust. The upper part of the crust probably averages about 8. The underlying mantle is denser and olivine- rich. The thickness of the crust ranges between about 2. Crust on the far side of the Moon averages about 1. Estimates of average thickness fall in the range from about 5. Most of this plagioclase- rich crust formed shortly after formation of the moon, between about 4. Perhaps 1. 0% or less of the crust consists of igneous rock added after the 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. Minor volcanism continued after 3. There is no evidence of plate tectonics.
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