Mechanical weathering occurs in many different ways.
Mechanical weathering, also referred to as "physical weathering," is the process of breaking and cracking big rocks into smaller rocks by physical force and without any chemical change to the rocks. Several different types of mechanical weathering exist, which are a result of different physical factors.
Frost Wedging
Frost wedging is a type of mechanical weathering that occurs when water seeps into the cracks and crevasses of rocks and boulders. The water then freezes and expands, eventually cracking and breaking apart the rocks from the inside out. Frost wedging typically occurs in areas with weather cold enough to freeze water, such as mountain areas.
Exfoliation
Exfoliation is a type of mechanical weathering that occurs when concentrated shells of weathering form on rocks and peel off in sheets. The exposed layer of rock then expands and results in exfoliation. This type of mechanical weathering typically occurs in areas containing plutonic igneous rocks, or rocks formed through solidified and cooling lava or magma.
Abrasion
Abrasion is a type of mechanical weathering that occurs when a rock's surface weathers due to the physical grinding of an abrasive agent, such as rock fragments. The friction of the abrasive agent gradually removes the outer layer of the rock. This type of mechanical weathering commonly occurs in deserts.
Thermal Expansion and Contraction
Thermal expansion and contraction is a type of mechanical weathering that occurs by the heating and cooling of rocks. During the hotter months, rocks will naturally heat and expand. During colder months, the rocks will naturally cool and contract. This constant cycle of expanding and contracting eventually will cause the rocks to fracture. This type of mechanical weathering is also common in deserts with high temperatures in the day and low temperatures at night.
Salt Wedging
Salt wedging is a type of mechanical weathering that occurs when water flows into the cracks of a rock and evaporates. The evaporated water leaves behind dissolved salt, which slowly forms into salt crystals and eventually wedges and cracks the rocks. This type of mechanical weathering commonly occurs in areas with arid climates.
Root Wedging
Root wedging is a type of mechanical weathering that occurs when roots and plants grow into rocks. During this process, tiny root hairs begin to grow in the pits and cracks of a rock. The root hairs continue to grow and expand, causing pressure on the rock, and eventually cracks and breaks the rock apart. This type of weathering is not specific to any climate or area.
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