Earth

• weathering - the breaking down of rocks by physical/mechanical, chemical or biological processes
• erosion - the gradual wearing away of rocks due to natural forces

  e.g. water, ice, wind, gravity
• There are 4 types of erosion: hydraulic action, abrasion, attrition, and solution
• hydraulic action - when water smashes against river banks causing them to crack/rocks to break off
• attrition - small rocks/pebbles collide, breaking off and becoming more round and smooth
• abrasion - large heavy rocks break into smaller rocks and damage the riverbed
• solution - when some of the rocks get dissolved by the water

  e.g. acidic water with limestone