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The colours indicate the age of oceanic crust, wherein lighter indicates younger age, and darker indicates older age. The lines represent tectonic plate boundaries. Continental and oceanic crust on the Earth's upper mantle. Oceanic crust is the uppermost layer of the oceanic portion of the tectonic plates.
Crustal growth rates can be used to calculate estimates for the age of the continental crust. This can be done through analysis of igneous rocks with the same isotopic composition as initial mantle rock. These igneous rocks are dated and assumed to be direct evidence of new continental crust formation. [22]
The estimated average density of the continental crust is 2.835 g/cm 3, with density increasing with depth from an average of 2.66 g/cm 3 in the uppermost crust to 3.1 g/cm 3 at the base of the crust. [13] In contrast to the continental crust, the oceanic crust is composed predominantly of pillow lava and sheeted dikes with the composition of ...
Continental crust – Layer of rock that forms the continents and continental shelves; Oceanic crust – Uppermost layer of the oceanic portion of a tectonic plate; Earth's mantle – A layer of silicate rock between Earth's crust and its outer core
The basement rocks of the continental crust tend to be much older than the oceanic crust. [3] The oceanic crust can be from 0–340 million years in age, with an average age of 64 million years. [4] Continental crust is older because continental crust is light and thick enough so it is not subducted, while oceanic crust is periodically ...
The thickness of Earth's crust (km). The continental crust consists of various layers, with a bulk composition that is intermediate (SiO 2 wt% = 60.6). [5] The average density of the continental crust is about, 2.83 g/cm 3 (0.102 lb/cu in), [6] less dense than the ultramafic material that makes up the mantle, which has a density of around 3.3 g/cm 3 (0.12 lb/cu in).
Oceanic lithosphere is associated with oceanic crust (having a mean density of about 2.9 grams per cubic centimetre or 0.10 pounds per cubic inch) and exists in the ocean basins. Continental lithosphere is associated with continental crust (having a mean density of about 2.7 grams per cubic centimetre or 0.098 pounds per cubic inch) and ...
Age of oceanic lithosphere. Beneath oceanic crust, the LAB ranges anywhere from 50 to 140 km in depth, except close to mid-ocean ridges where the LAB is no deeper than the depth of the new crust being created. [10] Seismic evidence shows that oceanic plates do thicken with age. This suggests that the LAB underneath oceanic lithosphere also ...