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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.
Artist's impression of Earth during its second eon, the Archean. The eon started with the Late Heavy Bombardment around 4.031 billion years ago. As depicted, Earth's planetary crust had largely cooled, leaving a water-rich barren surface marked by volcanoes and continents, eventually developing round microbialites.
The internal structure of Earth. In geology, the crust is the outermost solid shell of a planet, dwarf planet, or natural satellite.It is usually distinguished from the underlying mantle by its chemical makeup; however, in the case of icy satellites, it may be defined based on its phase (solid crust vs. liquid mantle).
The remaining 29.2% of Earth's crust is land, most of which is located in the form of continental landmasses within Earth's land hemisphere. Most of Earth's land is at least somewhat humid and covered by vegetation , while large sheets of ice at Earth's polar deserts retain more water than Earth's groundwater , lakes, rivers, and atmospheric ...
The tectonic plates of the lithosphere on Earth Earth cutaway from center to surface, the lithosphere comprising the crust and lithospheric mantle (detail not to scale). A lithosphere (from Ancient Greek λίθος (líthos) 'rocky' and σφαίρα (sphaíra) 'sphere') is the rigid, [1] outermost rocky shell of a terrestrial planet or natural satellite.
Tectonic plates are pieces of Earth's crust and uppermost mantle, together referred to as the lithosphere. The plates are around 100 km (62 mi) thick and consist of two principal types of material: oceanic crust (also called sima from silicon and magnesium ) and continental crust ( sial from silicon and aluminium ).
The structure's central uplift is known as the Vredefort Dome. The impact structure was formed during the Paleoproterozoic Era , 2.023 billion (± 4 million) years ago. It is the second-oldest known impact structure on Earth, after Yarrabubba .
The Earth's crust averages about 35 kilometres (22 mi) thick under the continents, but averages only some 7–10 kilometres (4.3–6.2 mi) beneath the oceans. The continental crust is composed primarily of sedimentary rocks resting on a crystalline basement formed of a great variety of metamorphic and igneous rocks, including granulite and granite.