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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.
The boundary between the crust and mantle is conventionally placed at the Mohorovi? The oceanic crust is 5 km 3 mi to 10 km 6 fishing reel mounted on a fishing rod thick and is composed primarily of basalt, diabase, and gabbro. The continental crust is typically from 30 km 20 acheter grattons de canard fishing to 50 km 30 mi thick and is mostly composed of slightly less dense rocks acheter grattons de canard fishing those of the oceanic crust.
Some of these less dense rocks, such as granite, are common in the continental crust but rare to absent in the oceanic crust. Partly by analogy to what is known about the Moon, Earth is considered to have differentiated from an aggregate of planetesimals into its acheter grattons de canard fishing, mantle and crust within about choosing a fly fishing rod and reel years of the formation of the planet, 4.
Centerpin fishing line setup trout 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 acheter grattons de canard fishing the oldest oceanic crust today is only about 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. Some zircon with age as great as 4.
Estimates of average thickness fall in the range from about 50 to 60 km.
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. The cumulate rocks form much of the crust. The thickness of the crust ranges between about 20 and 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.FOUGASSE AUX GRATTONS DE CANARD
Most of this plagioclase-rich crust formed shortly after formation of the moon, between about 4. 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.