Tectonics

Background

The Structure of the Earth

The inner core The heart of the Earth, its inner core, is a solid ball of iron and nickel. Here the pressure is so high that it never melts, despite the intense heat of 3700° Celcius.

The outer core The outer core is under less pressure so it is molten. It is made up of molten nickel and iron at a temperature of 2300° Celsius.

The mantle The outer core is enclosed by the mantle which is a deep layer over 3000 kilometers thick. It is composed mainly of silicate rocks, rich in iron and magnesium, which are at a temperature of 1000° Celsius. It is solid in places and molten in others.

The crust The crust forms the outer layer of the Earth. It comprises solid rock between 30 and 70 kilometers thick. Relatively speaking, this is very thin. If the Earth was a peach, the crust would be as thin as its skin. There are two types of crust:

1. Continental crust which corresponds approximately to the continental landmasses. Continental crust is thick and can be up to 65 kilometers deep. The continental crust is made of rocks such as granite, some of which were formed almost four thousand years ago.
2. Oceanic crust is much thinner and lies under the Earth's oceans. It consists of basalt, a much younger rock than granite, and its thickness is between 6 and 10 kilometers. At its deepest it has a temperature of 1000° Celsius.