Which statements describe physical weathering? Select all that apply.

Smal rocks are pushed together when a mole digs an underground den.

Mosses grow on a rock and produce acids that wear away the rock over time

Two rocks hit against each other in a fast flowing stream and break apart

Oxygen and water change the composition of the minerals in a rock

1 answer

Physical weathering refers to the mechanical processes that break down rocks without altering their chemical composition. Based on this definition, the statements that describe physical weathering are:

  1. Two rocks hit against each other in a fast flowing stream and break apart.

The other statements describe processes that involve chemical weathering or biological weathering:

  • Smal rocks are pushed together when a mole digs an underground den. (This could involve physical weathering, but it is not as direct an example as the statement about rocks in a stream.)

  • Mosses grow on a rock and produce acids that wear away the rock over time. (This is a form of biological weathering, which involves chemical processes due to the acids produced by the moss.)

  • Oxygen and water change the composition of the minerals in a rock. (This describes chemical weathering, not physical weathering.)

Thus, the only statement that clearly describes physical weathering is:

  • Two rocks hit against each other in a fast flowing stream and break apart.