What is Weathering?

• Animals an plants can wear away rocks. This is called Biological Weathering. For example, burrowing animals such as rabbits can burrow into the rocks, making it bigger and causing it to split.
• Another way biological weathering occurs is through roots in plants growing under concrete or rock causing it to split open allowng the plant to grow though.
• Sometimes people are the cause of biological weathering, mainly by walking. Overtime, paths in the counrtyside and busy town centres become damaged because of the continual wearing away from boots and shoes.

The weathering of rocks by chemicals is called chemical weathering. It is naturally sightly acidic because carbon dioxidefrom the air dissolves in it. Minerlas in rocks may react with rainwater, causing the rock to be weathered.

Somw types of rock are easily weathered by chemicals. For exmaple, limestone and chalk are made of a mineral called calcuim carbonate. When acidic rainwater falls on limestone or chalk a chemical reaction happens. New soluble substances are are formed in the reaction. These are washed away and the rock is weathered.

Physical weatherin is caused by the effects of changing temperature on rocks, cauing the rock to break apart. This process is sometimes assisted with water.

There are two main types of physical weathering:

• Freeze Thaw- occurs when water continually seeps into cracks, freezes and expands, eventually breaking the rock apart.
• Exfoliation- occurs as cracks develop parallel to the land surafce and asa consequence of the reduction in pressure during uplist and erosion.

Physical weathering happens especially in places where there is little soil and only few plants to grow, such as mountain regions and hot regions.

This occurs by repeating melting and freezing of water (mountains and tundra) or through contaction and expansion of the suface layer of rocks that are baked in the sun (hot regions)