A rock falling from a cliff is not an example of either chemical or mechanical weathering. It's an example of mass wasting.

Here's why:

* Weathering is the process of breaking down rocks, soil, and minerals through contact with the Earth's atmosphere, water, and biological organisms.

* Mechanical weathering involves the physical breakdown of rocks into smaller pieces without changing their chemical composition. Examples include frost wedging, abrasion, and root wedging.

* Chemical weathering involves the breakdown of rocks through chemical reactions, altering the composition of the rock. Examples include oxidation, hydrolysis, and dissolution.

* Mass wasting refers to the downhill movement of soil and rock under the influence of gravity. This can happen in various forms, including landslides, rockfalls, and mudflows.

The rock falling from the cliff is simply being moved by gravity, not broken down by weathering processes.