Answer:

1. Wind causes weathering by blowing bits of material against cliffs and large rocks.

2. Temperature changes can also contribute to mechanical weathering in a process called thermal stress.

3. Animals can walk on rock or disturb it, causing landslides that scrape or smooth rock surfaces.

4. Humans cause increases in acid rain and pollution, which increase the amount of weathering agents in the air and water, and then on land.

5. Water, in either liquid or solid form, is often a key agent of mechanical weathering.

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