Continental Crust

The continental crust is the layer of igneous, sedimentary, and metamorphic rocks which forms the continents and the areas of shallow seabed close to their shores, known as continental shelves. This layer is sometimes called sial because there is more felsic, or granitic, bulk composition, which lies in contrast to the oceanic crust, called sima because of the mafic or basaltic rock. (Based on the change in velocity of seismic waves, it is believed that at a certain depth sial becomes close in its physical properties to sima. This line is called the Conrad discontinuity.)

Consisting mostly of granitic rock, continental crust has a density of about 2.7 g/cm3 and is less dense than the material of the Earth's mantle (density of about 3.3 g/cm3), which consists of mafic rock. Continental crust is also less dense than oceanic crust (density of about 2.9 g/cm3), though it is considerably thicker; mostly 25 to 70 km versus the average oceanic thickness of around 7–10 km. About 40% of the Earth's surface is now overlaid by continental crust. Continental crust makes up about 70% of the volume of Earth's crust.

Read more about Continental Crust:  Importance, Origin, Forces At Work

Other articles related to "continental crust, crust, continental":

Continental Collision - Subduction Zone: The Collision Site
... The process begins as two continents (different bits of continental crust), separated across a tract of ocean (and oceanic crust), approach each other, while the ... the whole lithosphere, the density of which is largely controlled by the nature of the crust it carries ... Oceanic crust is thin (~6 km thick) and dense (about 3.3 g/cm³), consisting of basalt, gabbro, and peridotite ...
Anahim Hotspot - Petrology and Geochemistry
... Where hotspots occur under thick continental crust, basaltic magma is trapped in the less dense continental crust, which is heated and melts to form rhyolites ... Plate moves westwards, the Anahim hotspot underlies thinner continental crust ... In this case, the thinner crust would represent briefer travel time, thus reducing the time available for magma differentiation, whose end products are rhyolites ...
Continental Margin
... The continental margin is the zone of the ocean floor that separates the thin oceanic crust from thick continental crust ... Continental margins constitute about 28% of the oceanic area ... The transition from continental to oceanic crust commonly occurs within the outer part of the margin, called continental rise ...
Continental Crust - Forces At Work
... In contrast to the persistence of continental crust, the size, shape, and number of continents are constantly changing through geologic time ... There are currently about 7 billion cubic kilometers of continental crust, but this quantity varies because of the nature of the forces involved ... The relative permanence of continental crust contrasts with the short life of oceanic crust ...
Obduction
... Obduction is the overthrusting of continental crust by oceanic crust or mantle rocks at a convergent plate boundary ... usually subducts underneath the less dense continental plate ... Obduction occurs where a fragment of continental crust is caught in a subduction zone with resulting overthrusting of oceanic mafic and ultramafic rocks from ...

Famous quotes containing the word crust:

    Under the day’s crust a half-eaten child ...
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