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melony82 eNotes educator| Certified Educator

Plants can cause both mechanical and chemical weathering. 

Mechanical weathering occurs when roots grow and cause the rock to break (just like the roots that crack the sidewalk).  

Chemical weathering occurs when roots release chemicals, like acid, which then break down the rocks.

atyourservice | Student

The roots of plants can grow and slowly cause rocks to break as the pressure of their roots increase.