All rock material found on planet Earth is in the middle of constant, albeit slow, motion. Two phenomena affect this process known as the rock cycle: weathering and erosion.

Depending on external conditions, the rock cycle can move either very slowly or quite rapidly. The effects of this cyclical process are visible everywhere on planet Earth.

Weathering is a term that means the breaking down of rocks, stones, or minerals. As a result of weathering, the rocky surfaces our planet wear down and diminish gradually over the course of millennia.

The picture on the right shows a rock that has gained a face-like appearance as the result of weathering.

Erosion is a term that means the wearing down of rock and soil. Erosion is caused by flowing water, waves, the wind and glacial movement. These forces of erosion also transport and pile up the loose materials that they create. 

For example, the flowing water of a river wears down the riverbed, transports the loose material and piles it up near the mouth of the river, creating a delta. 


The sandstone arch has been eroded by wind.