“Crust” defines the outermost covering of a terrestrial planet. Our planet’s thin, 40-kilometer (25-mile) deep crust—just 1% of Earth’s mass—contains all recognized life in the universe.

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Earth has actually three layers: the crust, the mantle, and also the core. The crust is make of hard rocks and minerals. In ~ the crust is the mantle, which is likewise mostly hard rocks and minerals, but punctuated by malleableareas the semi-solid magma. In ~ the center of the planet is a hot, dense metal core.
Earth’s great constantly connect with each other, and the crust and also upper part of the mantle are part of a solitary geologic unit referred to as the lithosphere. The lithosphere’s depth varies, and the Mohorovicic discontinuity (the Moho)—the boundary in between the mantle and also crust—does no exist at a uniform depth. Isostasy describes the physical, chemical, and mechanical differences between the mantle and crust that enable the crust come “float” on the an ext malleable mantle. No all regions of earth are balanced in isostatic equilibrium. Isostatic equilibrium depends on the density and also thickness that the crust, and the dynamic pressures at work-related in the mantle.
Just together the depth the the tardy varies, therefore does its temperature. The upper crust withstands the approximately temperature of the environment or ocean—hot in arid deserts and also freezing in ocean trenches. Close to the Moho, the temperature of the crust varieties from 200° Celsius (392° Fahrenheit) to 400° Celsius (752° Fahrenheit).
Billions of years ago, the planetary blob that would become the earth started out as a hot, viscous sphere of rock. The heaviest material, mostly iron and nickel, sank to the center of the new planet and also became that is core. The molten product that surrounded the main point was the at an early stage mantle.
Over millions of years, the mantle cooled. Water trapped inside minerals erupted with lava, a procedure called “outgassing.” As an ext water to be outgassed, the mantle solidified. Materials that initially stayed in their liquid phase throughout this process, called “incompatible elements,” ultimately ended up being Earth’s brittle crust.
From mud and clay to diamonds and also coal, Earth’s crust is written of igneous, metamorphic, and sedimentary rocks. The many abundant rocks in the crust are igneous, i beg your pardon are formed by the cooling of magma. Earth’s late is affluent in igneous rocks such together granite and basalt. Metamorphic rocks have actually undergone drastic transforms due come heat and pressure. Slate and marble are acquainted metamorphic rocks. Sedimentary rocks are formed by the buildup of product at Earth’s surface. Sandstone and also shale space sedimentary rocks.
Dynamic geologic forces produced Earth’s crust, and the crust continues to be shame by the planet’s movement and also energy. Today, tectonic task is responsible because that the formation (and destruction) the crustal materials.
Earth’s crust is separated into two types: oceanic crust and continental crust. The shift zone between these two types of crust is sometimes referred to as the Conrad discontinuity. Silicates (mostly compounds made of silicon and oxygen) are the many abundant rocks and minerals in both oceanic and also continental crust.
Oceanic crust, prolonging 5-10 kilometers (3-6 kilometers) beneath the ocean floor, is mainly composed of different varieties of basalts. Geologists frequently refer to the rocks of the oceanic crust as “sima.” Sima means silicate and also magnesium, the many abundant mineral in oceanic crust. (Basalts are a sima rocks.) Oceanic tardy is dense, almost 3 grams per cubic centimeter (1.7 ounces per cubic inch).
Oceanic crust is constantly formed at mid-ocean ridges, where tectonic plates space tearing personal from every other. Together magma the wells up from these rifts in Earth’s surface cools, it i do not care young oceanic crust. The age and also density that oceanic crust increases with distance from mid-ocean ridges.
Just as oceanic tardy is created at mid-ocean ridges, the is damaged in subduction zones. Subduction is the vital geologic process in i m sorry a tectonic plate do of dense lithospheric material melts or falls below a plate made of less-dense lithosphere at a convergent bowl boundary.
At convergent bowl boundaries between continental and also oceanic lithosphere, the dense oceanic lithosphere (including the crust) always subducts beneath the continental. In the northwestern united States, for example, the oceanic Juan de Fuca bowl subducts in ~ the continent North American plate. In ~ convergent boundaries in between two plates transporting oceanic lithosphere, the denser (usually the larger and deeper ocean basin) subducts. In the Japan Trench, the dense Pacific bowl subducts beneath the less-dense Okhotsk plate.
As the lithosphere subducts, it sinks into the mantle, becoming much more plastic and also ductile. With mantle convection, the rich minerals the the mantle might be at some point “recycled” as they surface as crust-making lava at mid-ocean ridges and also volcanoes.
Largely as result of subduction, oceanic late is much, much younger than continental crust. The oldest existing oceanic crust is in the Ionian Sea, component of the eastern Mediterranean basin. The seafloor of the Ionian Sea is around 270 million years old. (The oldest parts of continental crust, on the various other hand, are much more than 4 billion year old.)
Geologists collect samples the oceanic crust through drilling at the s floor, making use of submersibles, and also studying ophiolites. Ophiolites space sections of oceanic crust that have been forced above sea level v tectonic activity, sometimes arising as dikes in continent crust. Ophiolites room often more accessible to researchers than oceanic crust in ~ the bottom of the ocean.
Continental tardy is largely composed of different species of granites. Geologists frequently refer come the rocks that the continental crust as “sial.” Sial represents silicate and aluminum, the most abundant minerals in continent crust. Sial can be lot thicker 보다 sima (as thick together 70 kilometers kilometers (44 miles)), but likewise slightly less dense (about 2.7 grams per cubic centimeter (1.6 ounces per cubic inch)).
As through oceanic crust, continent crust is created by bowl tectonics. At convergent bowl boundaries, whereby tectonic key crash right into each other, continent crust is thrust up in the process of orogeny, or mountain-building. Because that this reason, the thickest components of continental crust are at the world’s tallest mountain ranges. Prefer icebergs, the high peaks that the Himalayas and also the Andes room only component of the region’s continent crust—the late extends unevenly listed below the Earth and also soaring right into the atmosphere.
Cratons are the oldest and most stable component of the continental lithosphere. These components of the continent crust are usually found deep in the inner of most continents. Cratons are split into two categories. Shields space cratons in which the ancient basement rock crops out right into the atmosphere. Platforms space cratons in i beg your pardon the basement rock is buried beneath overlying sediment. Both shields and platforms provide crucial information come geologists around Earth’s early background and formation.
Continental tardy is practically always much older 보다 oceanic crust. Due to the fact that continental late is hardly ever destroyed and also recycled in the process of subduction, some sections of continental crust are virtually as old as the planet itself.
Our solar system’s various other terrestrial planets (Mercury, Venus, and also Mars) and also even our own Moon have actually crusts. Prefer Earth, these extraterrestrial crusts are developed mostly by silicate minerals. Uneven Earth, however, the crusts of these celestial bodies room not shaped by the communication tectonic plates.
Despite the Moon’s smaller sized size, lunar crust is thicker 보다 crust top top Earth. Lunar late is not a uniform thickness and also in general tends to it is in thicker top top the “far side,” which constantly faces away from Earth.
Although Mercury, Venus, and also Mars space not thought to have tectonic plates, they do have actually dynamic geology. Venus, because that instance, has at partly-molten mantle, yet the Venusian crust lacks enough trapped water to make it as dynamic together Earth’s crust.
The late of Mars, meanwhile, features the tallest mountains in the solar system. These hills are in reality extinct volcanoes created as molten absent erupted in the same spot top top the Martian surface ar over numerous years. Eruptions accumulated enormous mountains of iron-rich igneous rocks that give the Martian tardy its characteristics red hue.
One the the many volcanic crusts in the solar system is the of Jupiter’s moon Io. The well-off sulfide rocks in the Ionian crust repaint the moon a dappled arsenal of yellows, greens, reds, blacks, and also whites.

Earth"s crust is made of young oceanic material and also older, thicker continental material.

Map through USGS

The TauTona and Mponeng yellow mines of southern Africa space the deepest in the world, descending about 4 kilometers (2.5 miles) below the surface ar of the Earth. Return those space deep mines, they are shallow crust. Still, temperature at the bottom the the mines can climb come 55° Celsius (131° Fahrenheit). A sophisticated air conditioning system lowers the temperature to enable miners come work.
The oldest rocks yet established on planet were discovered in the Jack Hills of western Australia, part of the Yilgarn Craton, a shield formation. The Jack Hills zircons are around 4.4 billion years old. (The planet itself is around 4.6 billion years old!)
Silicate minerals, mostly feldspars and also quartz, space the many abundant minerals in Earth’s rocky crust.

our planet, the 3rd from the Sun. The earth is the only ar in the known universe that supports life.

in geochemistry, an facet that continues to be in a fluid phase throughout the melt or crystallization process.

equilibrium of Earth"s crust, where the pressures tending to elevate landmasses balance those tending to boring them. Also called isostatic equilibrium.

slow activity of Earth"s solid mantle resulted in by convection currents transferring warmth from the inner of the earth to the surface.

ancient rocks that formed as component of continent crust, currently overlain through sediment and also sedimentary rock, located in the interior of continents.

ancient rocks that created as part of continental crust and are located in the inner of continents.

movement of tectonic plates leading to geologic task such as volcanic eruptions and earthquakes.

massive slab of heavy rock comprised of Earth"s lithosphere (crust and upper mantle). Additionally called lithospheric plate.

areas in the Earth"s interior in between the upper mantle, near the Earth"s crust, and also the lower mantle, close to the Earth"s core.

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an opened in the Earth"s crust, through which lava, ash, and also gases erupt, and likewise the cone built by eruptions.


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