structure of the Earth
The Earth is formed of three concentric layers: the core, the mantle and the crust; these are separated by transition zones called discontinuities.
Layer from 30 to 60 mi thick that comprises the Earth’s crust and the solid part of the upper mantle; it is divided into tectonic plates.
Layer varying in thickness from 20 to 45 mi and composed mainly of granite. It forms a number of distinct landforms: the continents.
Layer of the upper mantle with a thickness of 125 mi; it is composed of molten rock, on top of which the lithospheric plates slide.
Zone that separates the Earth’s crust from the asthenosphere.
Zone separating the lower mantle from the core; it is located at a depth of about 1,800 mi.
Little-known layer with a thickness of about 1,420 mi; its slow-moving currents, called convection currents, are caused by temperature variations.
Composed of molten metal, it is 1,130 mi thick; the magnetic field is caused by electric currents circulating inside the outer core.
Composed of iron and nickel, it is subject to so much pressure that it remains in a solid state in spite of temperatures higher than 9,000°F; its diameter is 1,000 mi.
Layer forming the ocean floor; it is thinner, denser and younger than the continental crust.
Solid layer at the Earth’s surface whose thickness varies from 6 mi beneath the oceans to 35 mi beneath the mountains.
Layer of hard rock nearly 390 mi thick; it is made up of the asthenosphere and the base of the lithosphere.