Gravity is the driving force behind all agents of erosion. The process of erosion moves rock, soil and minerals from one location to another because of wind, running water, waves, glaciers and rain. Gravity forces rocks and soil downward from hilltops and mountains, thereby eroding the surface of the Earth. Precipitation falls to the Earth due to gravity, causing erosion from the water cycle.
Gravity affects several elements of erosion. Streams and rivers flow downstream because of the force of gravity along the gradient or slope of the waterway. Water carries silt and sediments away from their origination point and deposits these soils further downstream. Water falls on hillsides as rain and rushes down the side of the elevated landform. The moving water weakens compacted dirt that eventually gives way and falls downhill.
Gravity drives erosion in glaciers due to the crushing weight of the thick ice above the ground. More fundamentally, precipitation that forms glacial ice falls to the Earth's surface due to the pull of gravity. When materials are carried by wind, dust particles eventually fall back to the surface because of the planet's gravitational pull.
Erosion normally happens slowly over time, as in the case of the Grand Canyon in the United States. More extreme examples of sudden erosion occur in mudslides and floods when massive amounts of material are transported in a short period of time.