Abrasion in action.
Mechanical weathering is a term geologists use to describe the group of natural forces that act on larger rocks to break them down into smaller ones. Here are some examples of how mechanical weathering works.
When water freezes, it expands. So when water gets trapped in the pores and crevices of a rock then freezes, it can push the rock apart, causing it to break. Some minerals, like calcium carbonate, can have a similar effect.
Growing bacteria, plant and tree roots can destroy a rock by working their way down into its nooks and crannies, forcing the rock apart and causing it to break into smaller pieces.
In areas where the temperature fluctuates dramatically, rock can expand and contract over a very short period of time, weakening it and causing breaks.
Rocks formed under the Earth’s surface are subjected to tremendous pressure. As those rocks are moved toward the Earth’s surface, pressure is released and the rock expands, which can lead to fracturing.
The movements of water and wind can expose rocks to friction and abrasion from other rocks, particles and surfaces, causing them to break apart.