Interactive multiple-choice quiz: Changing Earth's Surface

The surface of the Earth is constantly changing through geological processes such as weathering, erosion, and deposition. Weathering breaks rocks down into sediment, either physically—like when plant roots pry apart stones—or chemically, such as when acidic groundwater dissolves rock to form caves. Erosion then transports these materials via water, wind, or glaciers. In rivers, water flows faster on the outside of bends, causing erosion, while glaciers carve out massive U-shaped valleys and leave behind unsorted sediments called till. Fine silt and clay deposited by wind is known as loess. These processes are governed by the principle of uniformitarianism, which states that the same geologic laws observed today have operated throughout Earth's long history.