When atmospheric carbon dioxide reacts with water in the atmosphere, it forms carbonic acid. This acid can then react with some forms of rock, weakening it and changing its chemical composition. What is this known as?

The terms used to describe the given process in Chemical weathering.

Explanation:

Weathering of rock is defined as breaking down of the rock into small pieces.

There are two types pf weathering:

Mechanical weathering : This weathering is due to change in physical parameters : temperature change, pressure change etc.

For example : When water soaked up in cracks or crevices of rocks freezes it expands and physically breaks the rock.

Chemical weathering : This weathering is decomposition of rocks due to action of chemicals. This type of weathering also changes chemical composition of rocks.

For example : when gases like carbon dioxide, sulfur oxide get dissolves in water present in rock to form weak acid which ease up the dissolving of rock in that weak acid.