New! Sign up for our free email newsletter.
Reference Terms
from Wikipedia, the free encyclopedia

Crust (geology)

In geology, a crust is the outermost layer of a planet.

The crust of the Earth is composed of a great variety of igneous, metamorphic, and sedimentary rocks. The crust is underlain by the mantle. The upper part of the mantle is composed mostly of peridotite, a rock denser than rocks common in the overlying crust. The boundary between the crust and mantle is conventionally placed at the Mohorovicic discontinuity, a boundary defined by a contrast in seismic velocity. Earth's crust occupies less than 1% of Earth's volume.

The oceanic crust of the Earth is different from its continental crust. The oceanic crust is 5 km (3 mi) to 10 km (6 mi) thick and is composed primarily of basalt, diabase, and gabbro. The continental crust is typically from 30 km (20 mi) to 50 km (30 mi) thick, and it is mostly composed of less dense rocks than is the oceanic crust. Some of these less dense rocks, such as granite, are common in the continental crust but rare to absent in the oceanic crust.

The temperature of the crust increases with depth, reaching values typically in the range from about 500 °C (900 °F) to 1,000 °C (1,800 °F) at the boundary with the underlying mantle. The crust and underlying relatively rigid mantle make up the lithosphere. Because of convection in the underlying plastic, although non-molten, upper mantle and asthenosphere, the lithosphere is broken into tectonic plates that move.

The common rock constituents of the Earth's crust are nearly all oxides; chlorine, sulfur and fluorine are the only important exceptions to this and their total amount in any rock is usually much less than 1%. F. W. Clarke calculated that a little more than 47% of the Earth's crust consists of oxygen. It occurs principally in combination as oxides, of which the chief are silicon, aluminum, iron, calcium, magnesium, potassium and sodium oxides. Silica is a major constituent of the crust occurring as the silicate minerals, which are the most common minerals of igneous and metamorphic rocks.

Related Stories
 


Earth & Climate News

August 1, 2025

A Penn State-led research team has unraveled the long-standing mystery of how lightning begins inside thunderclouds. Their findings offer the first quantitative, physics-based explanation for lightning initiation—and a glimpse into the stormy ...
A jaw-dropping 515-mile lightning bolt lit up the skies from Texas to Kansas City, smashing previous records and reshaping our understanding of extreme weather. Thanks to advanced satellite tech, scientists like Randy Cerveny and Michael Peterson ...
A team at the University of Florida used drones and smart modeling to accurately count over 41,000 endangered turtles nesting along the Amazon’s Guaporé River—revealing the world’s largest known turtle nesting site. Their innovative ...
Researchers are exploring AI-powered digital twins as a game-changing tool to accelerate the clean energy transition. These digital models simulate and optimize real-world energy systems like wind, solar, geothermal, hydro, and biomass. But while ...
Deep in Serbia's Jadar Valley, scientists discovered a mineral with an uncanny resemblance to Superman's Kryptonite both in composition and name. Dubbed jadarite, this dull white crystal lacks the ...
Mesopelagic fish, long overlooked in ocean chemistry, are now proven to excrete carbonate minerals much like their shallow-water counterparts—despite living in dark, high-pressure depths. Using the deep-dwelling blackbelly rosefish, researchers ...
For over two decades, satellites have quietly documented a major crisis unfolding beneath our feet: Earth's continents are drying out at unprecedented rates. Fueled by climate change, groundwater ...
Air pollution isn't just bad for your lungs—it may be eroding your brain. In a sweeping review covering nearly 30 million people, researchers found that common pollutants like PM2.5, nitrogen ...
A new eco-friendly plastic called LAHB has shown it can biodegrade even in the extreme environment of the deep ocean, unlike conventional plastics that persist for decades. In real-world underwater testing nearly a kilometer below the surface, LAHB ...
In 2023, the world’s oceans experienced the most intense and widespread marine heatwaves ever recorded, with some events persisting for over 500 days and covering nearly the entire globe. These ...
Imagine concrete that not only survives wildfires and extreme weather, but heals itself and absorbs carbon from the air. Scientists at USC have created an AI model called Allegro-FM that simulates billions of atoms at once, helping design futuristic ...
Scientists have discovered that pairing bread wheat with a special soil fungus can significantly enhance its nutritional value. This partnership leads to bigger grains rich in zinc and phosphorus—without increasing anti-nutrients that block ...

Latest Headlines

updated 12:56 pm ET