Exogenic processes are processes that take place at or near the Earth's surface that cause the surface to wear away through physical and chemical weathering. Physical weathering breaks rock into smaller pieces through processes like ice wedging, plant growth, animal activity, and abrasion. Chemical weathering breaks down rock through chemical changes caused by water, oxygen, carbon dioxide, living organisms, and acid rain. Erosion by water, wind, ice, and gravity further transports weathered materials and shapes the landscape over time through sedimentation and mass wasting.