“Crust” describes 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 well-known life in the universe.

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Earth has three layers: the crust, the mantle, and also the core. The tardy is do of solid rocks and also minerals. In ~ the late is the mantle, i m sorry is additionally mostly hard rocks and also minerals, yet punctuated by malleableareas that semi-solid magma. In ~ the center of the planet is a hot, dense metal core.
Earth’s layers constantly communicate with every other, and the crust and upper portion of the mantle are part of a single geologic unit called the lithosphere. The lithosphere’s depth varies, and the Mohorovicic discontinuity (the Moho)—the boundary between the mantle and crust—does not exist in ~ a uniform depth. Isostasy explains the physical, chemical, and mechanical differences between the mantle and crust that permit the crust come “float” top top the more malleable mantle. No all areas of planet are well balanced in isostatic equilibrium. Isostatic equilibrium relies on the density and also thickness that the crust, and also the dynamic forces at job-related in the mantle.
Just as the depth that the crust varies, so does its temperature. The upper crust withstands the ambient temperature of the atmosphere or ocean—hot in arid deserts and also freezing in ocean trenches. Close to the Moho, the temperature the the crust arrays from 200° Celsius (392° Fahrenheit) come 400° Celsius (752° Fahrenheit).
Billions of year ago, the planetary blob that would come to be the planet started out as a hot, viscous ball of rock. The most difficult material, greatly iron and also nickel, sank to the facility of the brand-new planet and became that is core. The molten product that surrounding the core was the early mantle.
Over countless years, the mantle cooled. Water trapped within minerals erupted v 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 come diamonds and coal, Earth’s tardy is written of igneous, metamorphic, and sedimentary rocks. The most abundant rocks in the crust are igneous, i beg your pardon are formed by the cooling the magma. Earth’s crust is affluent in igneous rocks such together granite and also basalt. Metamorphic rocks have undergone drastic changes due to heat and also pressure. Slate and also marble are acquainted metamorphic rocks. Sedimentary rocks are formed by the accumulation of material at Earth’s surface. Sandstone and shale space sedimentary rocks.
Dynamic geologic forces developed Earth’s crust, and also the crust continues to be shaped by the planet’s movement and energy. Today, tectonic task is responsible because that the development (and destruction) of crustal materials.
Earth’s late is divided into two types: oceanic crust and continental crust. The shift zone between these two types of late is sometimes called the Conrad discontinuity. Silicates (mostly compounds made of silicon and also oxygen) room the most abundant rocks and also minerals in both oceanic and continental crust.
Oceanic crust, expanding 5-10 kilometers (3-6 kilometers) in ~ the s floor, is largely composed that different varieties of basalts. Geologists often refer come the rocks of the oceanic crust as “sima.” Sima means silicate and magnesium, the most abundant mineral in oceanic crust. (Basalts are a sima rocks.) Oceanic late is dense, almost 3 grams per cubic centimeter (1.7 ounces every cubic inch).
Oceanic tardy is constantly created at mid-ocean ridges, whereby tectonic plates space tearing personally from each other. As magma the wells increase from this rifts in Earth’s surface cools, it becomes young oceanic crust. The age and density the oceanic crust boosts with distance from mid-ocean ridges.
Just as oceanic late is developed at mid-ocean ridges, that is destroyed in subduction zones. Subduction is the essential geologic procedure in i beg your pardon a tectonic plate do of dense lithospheric material melts or falls below a plate make of less-dense lithosphere in ~ a convergent bowl boundary.
At convergent plate boundaries between continental and also oceanic lithosphere, the dense oceanic lithosphere (including the crust) always subducts in ~ the continental. In the northwestern joined States, because that example, the oceanic Juan de Fuca plate subducts in ~ the continent North American plate. In ~ convergent boundaries in between two plates transferring oceanic lithosphere, the denser (usually the larger and also deeper ocean basin) subducts. In the Japan Trench, the dense Pacific plate subducts beneath the less-dense Okhotsk plate.
As the lithosphere subducts, the sinks into the mantle, becoming much more plastic and ductile. Through mantle convection, the well-off minerals the the mantle might be at some point “recycled” together they surface ar as crust-making lava at mid-ocean ridges and also volcanoes.
Largely as result of subduction, oceanic tardy is much, much younger 보다 continental crust. The earliest existing oceanic tardy is in the Ionian Sea, component of the east Mediterranean basin. The seafloor that the Ionian Sea is about 270 million year old. (The earliest parts of continental crust, top top the various other hand, are more than 4 billion year old.)
Geologists collect samples of oceanic crust v drilling at the s floor, making use of submersibles, and studying ophiolites. Ophiolites room sections that oceanic tardy that have been forced above sea level through tectonic activity, sometimes emerging as dikes in continental crust. Ophiolites room often an ext accessible to researchers than oceanic crust at the bottom that the ocean.
Continental crust is mainly composed of different types of granites. Geologists regularly refer to the rocks the the continental crust together “sial.” Sial stands for silicate and also aluminum, the most abundant minerals in continental crust. Sial can be lot thicker than sima (as thick together 70 kilometers kilometers (44 miles)), but additionally slightly less thick (about 2.7 grams every cubic centimeter (1.6 ounces per cubic inch)).
As with oceanic crust, continental crust is produced by plate tectonics. In ~ convergent bowl boundaries, where tectonic plates crash right into each other, continent crust is thrust increase in the procedure of orogeny, or mountain-building. Because that this reason, the thickest parts of continent crust room at the world’s tallest hill ranges. Like icebergs, the tall peaks that the Himalayas and also the Andes space only component of the region’s continental crust—the crust extends unevenly listed below the Earth as well as soaring into the atmosphere.
Cratons room the oldest and most stable part of the continental lithosphere. These parts of the continental crust room usually discovered deep in the internal of most continents. Cratons are separated into two categories. Shields are cratons in i m sorry the old basement rock plants out into the atmosphere. Platforms space cratons in i beg your pardon the basement absent is hidden beneath overlying sediment. Both shields and platforms provide an essential information come geologists around Earth’s early background and formation.
Continental late is almost always lot older than oceanic crust. Because continental tardy is seldom destroyed and recycled in the procedure of subduction, part sections of continental crust are almost as old as the earth itself.
Our solar system’s various other terrestrial planets (Mercury, Venus, and Mars) and even our very 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 are not shaped by the communication tectonic plates.
Despite the Moon’s smaller sized size, lunar late is thicker 보다 crust ~ above Earth. Lunar tardy is no a uniform thickness and also in general tends to be thicker on the “far side,” which always faces away from Earth.
Although Mercury, Venus, and Mars room not assumed to have actually tectonic plates, they do have dynamic geology. Venus, because that instance, has at partly-molten mantle, however the Venusian late lacks enough trapped water to do it as dynamic as Earth’s crust.
The crust of Mars, meanwhile, attributes the tallest hills in the solar system. These mountains are in reality extinct volcanoes formed as molten rock erupted in the exact same spot on the Martian surface ar over numerous years. Eruptions gathered enormous hills of iron-rich igneous rocks that offer the Martian tardy its characteristic red hue.
One that the most volcanic crusts in the solar device is that of Jupiter’s moon Io. The affluent sulfide rocks in the Ionian crust paint the moon a dappled repertoire of yellows, greens, reds, blacks, and also whites.

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

Map by USGS

The TauTona and Mponeng yellow mines of southern Africa are the deepest in the world, descending about 4 kilometers (2.5 miles) below the surface of the Earth. Back 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 device lowers the temperature to enable miners come work.
The earliest rocks yet determined on earth were found in the Jack Hills of west Australia, component of the Yilgarn Craton, a shield formation. The Jack Hills zircons are about 4.4 billion year old. (The earth itself is about 4.6 billion year old!)
Silicate minerals, mainly feldspars and quartz, are the many abundant minerals in Earth’s rocky crust.

our planet, the third from the Sun. The earth is the only ar in the well-known universe that supports life.

in geochemistry, an element that stays in a fluid phase throughout the melt or crystallization process.

equilibrium that Earth"s crust, whereby the pressures tending come elevate landmasses balance those tending to depress them. Also called isostatic equilibrium.

slow movement of Earth"s solid mantle resulted in by convection currents transferring warm from the inner of the planet to the surface.

ancient rocks that created as component of continental crust, currently overlain through sediment and sedimentary rock, located in the inner of continents.

ancient rocks that formed as component of continental crust and also are located in the internal of continents.

movement the tectonic plates leading to geologic activity such together volcanic eruptions and also earthquakes.

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

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

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


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