Why is the earth's crust getting warmer?

Volcanoes for schoolchildren

The structure of the earth

To understand how volcanoes work, you need to know how our planet earth is built. The earth is not a solid body through and through. It consists of several different layers, some of which are almost liquid. Our planet can best be compared to a peach: like a peach, the earth has a skin, pulp and a core. The solid skin of the earth is the earth's crust, the outermost view on which we live. Below the earth's crust is the earth's mantle. In the case of our peach, this corresponds to the pulp. The core of the earth lies below the earth's mantle.

Imagine going on a journey into the interior of the earth: The first few kilometers lead you through solid rock. After just a few kilometers you will feel that it is getting warmer and warmer. In the upper part of the earth's crust, the temperature increases by 3 degrees Celsius per 100 m. After about 30 kilometers it gets so hot that solid rock melts. It becomes magma. The temperatures down here are higher than in a normal fire, it is around 900 ° C here. Although the rock melts, it does not become liquid.
The pressure at this depth is too high for that. Instead of becoming liquid, the rock behaves like plasticine. It becomes plastic. You are now in the earth's mantle. There is practically no solid rock left here, only magma. The temperatures in the earth's mantle are around 2500 ° C. It's much hotter than in a blast furnace. You keep traveling further and further into the earth. After 2900 kilometers you will reach the outer core of the earth. The earth's core no longer consists of magma, but of iron and another metal, nickel. Temperatures of 5500 ° C prevail in the lower core of the earth. It's as hot as the sun's surface! In the outer area of ​​the earth's core, the metals are still liquid. In the middle of the earth, the pressure is so great that the metals are solid again despite the great heat.

Can you imagine what the purpose of a volcanic eruption is?