Mantle is the layer of rock between Earth’s crust and core. The mantle makes up approximately 83 percent of Earth’s volume and about 67 percent of its mass (amount of matter). Movements within the mantle cause volcanic eruptions, most earthquakes, and continental drift (the slow movement of land masses). Mercury, Venus, and Mars also have mantles.
Most of Earth’s mantle rock is peridotite << `pehr` uh DOH tyt >>, which is composed mostly of silicon, oxygen, iron, and magnesium. The most abundant mineral in the peridotite is olivine << AHL uh veen >>.
The mantle is about 1,800 miles (2,900 kilometers) thick. The top of the mantle lies about 5 miles (8 kilometers) beneath the ocean floor. Under the continents, the average depth of the top of the mantle is about 25 miles (40 kilometers).
The temperature at the top of the mantle is about 1800 °F (1000 °C) under continental crust. At the bottom, where the mantle contacts Earth’s outer core, the temperature is roughly 7000 °F (4000 °C).
Mantle rock that is hotter than about 2400 °F (1300 °C) can flow much as a glacier creeps down a mountain valley. Over much of Earth, from depths of about 60 to 150 miles (100 to 240 kilometers), the mantle is partly molten (melted). This part of the mantle, known as the asthenosphere << as THEHN uh sfihr >>, is very weak.
The cooler overlying mantle and the crust make up huge lithospheric plates that move slowly on the asthenosphere. The continents are embedded in the tops of some plates, and so plate movement causes continental drift.
