Chemical weathering

The process

By which rocks are broken down by chemical reactions:

Exposure to things such as water, oxygen, carbon dioxide and axis can alter the minerals found in rocks.

After chemical weathering, we end up with a different substance than the one started with.


The chemical breakdown of a substance combined with water.

Chemical reaction happening between the minerals found in the Rock and rain water.

When it rains, water seeps down into the ground and comes in contacts with granite rocks. The feldspar crystals within the granite react with the water and are chemically altered to form clay minerals, weakening the rock.


The reaction of a substance with oxygen

The process causes rust

Rocks can get rusty if they contain iron. When iron reacts with oxygen, it forms iron oxide (not strong)

When a rock gets oxidised, it is weakened and crumbles easily, and breaks down


Mixing of water with carbon dioxide to make carbonic acid (important in the formation of caves).

Dissolved carbon dioxide in rainwater or moist air forms carbonic acid, which reacts with the minerals In rocks (calcite mineral)

This mineral dissolves in the carbonic acid and gets washed away.

Hollows out the Rock and leaves a cave behind

Lichens and acid rain

Combinations of fungi and algae and grow on rocks and produce acid that break down the minerals within rocks. Water mixes with the lichens, producing a weak acid.

A very slow process (common type of chemical weathering)

Occurs near rivers and streams.

Lichens breakdown rock by producing an acid (similar to acid drain).

Acid rain is rain that has been made of acidic by certain pollutants in the air.

The process produces acids which fall to the ground