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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).
Continental crust is a tertiary crust, formed at subduction zones through recycling of subducted secondary (oceanic) crust. [17] The average age of Earth's current continental crust has been estimated to be about 2.0 billion years. [20] Most crustal rocks formed before 2.5 billion years ago are located in cratons.
Earth's crust – Earth's outer shell of rock 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
Characteristic of subduction zones, andesite represents the dominant rock type in island arcs. The average composition of the continental crust is andesitic. [3] Along with basalts, andesites are a component of the Martian crust. The name andesite is derived from the Andes mountain range, where
Granitic rock is widely distributed throughout the continental crust. [18] Much of it was intruded during the Precambrian age; it is the most abundant basement rock that underlies the relatively thin sedimentary veneer of the continents. Outcrops of granite tend to form tors, domes or bornhardts, and rounded massifs.
The thin parts are the oceanic crust, which underlies the ocean basins (5–10 km) and is mafic-rich [9] (dense iron-magnesium silicate mineral or igneous rock). [10] The thicker crust is the continental crust, which is less dense [11] and is felsic-rich (igneous rocks rich in elements that form feldspar and quartz). [12]
Zealandia, considered a candidate for the Earth’s eighth continent, was mostly lost to the sea. Geologists say they’ve now mapped the entire nearly two million square miles of the underwater ...
The Australian continental crust, excluding the thinned margins, has an average thickness of 38 kilometres (24 mi), with a range in thickness from 24 to 59 kilometres (15 to 37 mi). [1] The continental crust is composed primarily of Archaean, Proterozoic and some Palaeozoic granites and gneisses.