Earth’s Interior
E
arth’s interior is divided into layers: the crust, mantle,
outer core, and inner core. Although Earth’s crust
seems stable, the extreme heat of Earth’s interior causes
changes that slowly reshape the surface.
CRUST
The crust is Earth’s solid and
rocky outer layer, including both
the land surface and the ocean
floor. The crust averages 32 km
thick. At the scale of this drawing,
the crust is too thin to show up
as more than a thin line.
䉳 CROSS-SECTION FROM
SURFACE TO CENTER
From Earth’s surface to its center, the layers of
Earth’s interior differ in their composition,
temperature, and pressure. Notice how
temperature increases toward the inner core.
Composition of crust:
oxygen, silicon, aluminum,
calcium, iron, sodium,
potassium, magnesium
CRUST-TO-MANTLE
The rigid crust and lithosphere float on the hot,
plastic material of the asthenosphere. Notice that
continental crust, made mostly of granite, is
several times thicker than oceanic crust, made
mostly of basalt. 䉲
CORE
MANTLE
A trip through Earth’s mantle goes almost halfway
to the center of Earth. The chemical composition
of the mantle does not change much from one
part of the mantle to another. However, physical
conditions in the mantle change because pressure
and temperature increase with depth.
Composition of mantle:
silicon, oxygen, iron, magnesium
Scientists estimate that temperatures within Earth’s outer core
and inner core, both made of
iron and nickel, range from
about 2,000°C to 5,000°C. If
these estimates are correct, then
Earth’s center may be as hot as
the sun’s surface.
Composition of core:
iron, nickel