Question

why iron oxide weakens the rocks?(oxidation)

Answer 1

Oxidation is the reaction of a substance with oxygen. You are probably familiar with oxidation because it is the process that causes rust. So, just like your car turns to rust through oxidation, rocks can get rusty if they contain iron.

You may have noticed that rusted metal on your car is somewhat fragile; you could even poke your finger through a rust patch if it's big enough. This is because, when iron reacts with oxygen, it forms iron oxide, which is not very strong. So, when a rock gets oxidized, it is weakened and crumbles easily, allowing the rock to break down. Iron oxide is kind of brownish-red in color, and this explains why some rocks look red