How does weathering and erosion work

Erosion and weathering

Without them our world would certainly look different: there would be no deep ravines and no dark caves, the mountains would grow endlessly into the sky and the soil would be sterile. Weathering and erosion change the landscape mostly unnoticed and at the same time it is impossible to imagine the earth system without it.

We even encounter weathering in everyday life: a rusting car on the side of the road, the old newspaper lying in tatters on the sidewalk or the crumbling plaster on house facades. Who suspects that the same processes are responsible for this, which also form caves, remove mountains or create valleys?

A rock fall in the Alps is the beginning of a long journey for the rock as river gravel to the Atlantic. The limestone dissolved by rainwater in the karst landscapes of Croatia ends up in the sea via the detour of the groundwater at some point. And the rainforest of South America can only survive with a regular nutrient shower with fresh Saharan dust, brought in by the steady westerly winds from Africa.

Day after day, the sun, wind and rain gnaw everything that is on the surface of the earth. The weathering either chemically or mechanically crushes any rock, no matter how hard, and the erosion transports this more or less coarse rubble to another place - starting material for fertile soils or new sedimentary rocks.

But what chemical reactions can water use to hollow out even the hardest rock in the truest sense of the word? And why does an inscription on old gravestones fade faster in England than in Egypt? Anyone who has ever walked on the beach in a “stiff breeze” knows the abrasive effect of winds containing sand. But who has ever heard of core jumps and fractal banks? The fact that river gravel is angular in the upper reaches and round in the lower reaches can perhaps still be explained, but why does the cultivation of maize or sugar beet promote the erosion of arable land?

The list of factors that influence weathering and erosion seems seemingly endless: the important thing is the composition of the rock, the dryness or humidity of the climate, the strength and direction of the wind or the acidity of the water. In addition, there is the degree of vegetation cover, the shape of the terrain or the orientation towards the sun. Whatever the situation of the "attacked" rock, one thing is certain: Nothing and no one can escape weathering and subsequent erosion ...

Andreas Heitkamp
Status: 04.03.2005

March 4, 2005