Animation of physiscal and chemical weathering

Weathering

The earth is build up by endogenous forces. These are forces that arise through the magma flows within the earth. But, mountains are also broken down again. This is caused by endogenous forces. These forces are caused by external influences. The most important influence from outside the earth is the sun. Further, the moon and meteorites play a very small role in shaping the landscape.

The degradation of rock is called weathering. This means that rock is broken. We divide weathering into 2 types: chemical weathering and physical or mechanical weathering. Mechanical weathering is in turn subdivided into 3 types of weathering: weathering due to temperature differences, frost weathering and weathering by plant roots.

We see weathering through temperature differences mainly in deserts. Stones warm up all day. Because of that heat, the stone expands. At night the temperature cools considerably and the stone shrinks. This goes on for a long time. Because the outside mainly heats up and cools down, and therefore only the outer layer expands and shrinks, there is tension in the stone that leads to cracks in the stone and the stone eventually falls apart.

Frost weathering is mainly seen in mountains and other cold areas. Water can penetrate into small cracks in stones. In cold areas the water can freeze, where it expands. This breaks the stone. This creates more room for water to get into the cracks, so that next time the stone can be pushed further apart. A somewhat humid environment is therefore required for this type of weathering and the temperature must be around the freezing point so that the water can freeze and thaw.

Weathering by plant roots has a resemblance to frost weathering, only here are the plant roots that push the stone apart. Roots can come into cracks in the stone. When trees grow, the roots become thicker. In this way they can push stones apart.

In addition to mechanical weathering, there is also chemical weathering. Chemical weathering means that rock is disintegrated by a chemical reaction. Chemical weathering generally occurs when some rocks come into contact with water or oxygen. When there is more carbon dioxide or CO2 in the water, the water becomes more acidic, causing chemical weathering to occur even faster. More CO2 in the atmosphere thus leads to acid rain, causing more chemical weathering.

Chemical weathering is most clearly visible in limestone caves. Water has dissolved the limestone, creating caves. Later, stalagmites and stalactites can arise here, which provide beautiful caves. When caves become too large, they can collapse.


So by different forms of weathering, rock can be broken down.