Inside the
Earth
The Earth is made
of many different and distinct layers. The deeper layers
are composed of heavier materials; they are hotter, denser
and under much greater pressure than the outer layers.
Core: The Earth has a iron-nickel core that is about 2,100
miles in radius. The inner core may have a temperature up
to about 13,000°F (7,200°C = 7,500 K), which is hotter
than the surface of the
Sun. The inner core
(which has a radius of about 750 miles (1,228 km) is
solid. The outer core is in a liquid state and is about
1,400 miles (2,260 km) thick.
Mantle: Under the
crust is the rocky mantle, which is composed of silicon,
oxygen, magnesium, iron, aluminum, and calcium. The upper
mantle is rigid and is part of the lithosphere (together
with the crust). The lower mantle flows slowly, at a rate
of a few centimeters per year. The asthenosphere is a part
of the upper mantle that exhibits plastic properties. It
is located below the lithosphere (the crust and upper
mantle), between about 100 and 250 kilometers deep.
Surface and
crust: The Earth's surface is composed mostly of water,
basalt and granite. Oceans cover about 70% of Earth's
surface. These oceans are up to 3.7 km deep. The Earth's
thin, rocky crust is composed of silicon, aluminum,
calcium, sodium and potassium. For a page on soil, click
here.
