The question asks us to pick the one process out of four that is physical, or mechanical, weathering, meaning it breaks rock apart without changing what the minerals are made of.
- Oxidation: This is a reaction between minerals and oxygen, usually seen as rust forming on iron bearing minerals. Since a new mineral forms, this is chemical weathering, not physical.
- Hydrolysis: Water reacts with minerals like feldspar and breaks their structure down into clay minerals. Since the chemistry changes, this is also chemical weathering.
- Exfoliation: This is the peeling away of curved rock sheets, mainly caused by pressure release when overlying rock erodes, or by repeated expansion and contraction from heating and cooling. No chemical change happens, only physical splitting, so this is mechanical weathering.
- Carbonation: Dissolved carbon dioxide reacts with minerals such as calcite to form bicarbonates that can dissolve away. This is a chemical reaction, so it counts as chemical weathering.
Out of the four, only exfoliation involves no chemical change, just physical splitting of rock into sheets. That makes it the physical weathering process.
Let's summarize:
- Oxidation, hydrolysis and carbonation all involve a chemical reaction that changes the minerals.
- Exfoliation only breaks the rock apart mechanically, driven by pressure release or temperature change.
So the correct answer is exfoliation.