Environmental Engineering Reference
In-Depth Information
Why the Earth's Inner Core is Not Liquid
The earth's inner core, which essentially consists of iron and nickel, has
temperatures of up to 6500 °C. Under normal environmental conditions with
an ambient pressure of one bar, these temperatures would make iron and nickel gaseous.
The pressure rises as the depth into the earth's interior increases. This pressure reaches
maximum values of four million bars. This extremely high pressure ensures that the
outer core is liquid and the inner core is solid.
Eighty percent of the earth's core consists of iron. A small amount of the heat in
the earth's interior comes from residual heat from the time earth was formed but a
major part consists of radioactive decaying processes. The earth's mantle is around
2900 km thick. We are only able to reach the top part of the earth's crust.
The earth's crust and the uppermost part of the earth's mantle form the lithosphere.
The thickness of the lithosphere varies from a few kilometres to more than 100 km.
It consists of seven large and some smaller lithosphere plates (Figure 10.3). These
rather brittle plates fl oat in the asthenosphere, where matter is no longer solid. The
plates are constantly in motion. Earthquakes and volcanoes frequently occur in areas
where two plates collide. Thermal anomalies can also frequently be observed in
these areas. High temperatures can occur there even at shallow depths, creating
conditions that enable us to make particularly effective use of the earth's heat.
Figure 10.3 Tectonic plates on earth. Source: US Geological Survey.
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