Weathering The process by which rocks are broken into smaller pieces. It can be mechanical or chemical Erosion The word "erosion" comes from an old word meaning "eat away.” You see erosion happening where the forces of nature move soil and rock. These agents of erosion are water, wind, ice and gravity. A physical process involving no change in chemical composition. The rock is simply broken down into small fragments by various methods. Freezing water expands in cracks and wedges the rock apart. The grinding and wearing away of rock. Wind, water, and gravity can lead to abrasion. Caused by water, weak acids, and air. Acids are created by volcanic activity and pollution. Acids can be created by water reacting with limestone. The combination of oxygen in the atmosphere with a mineral to produce an oxide - high iron content rocks are particularly vulnerable. If a particle is loosened, chemically or mechanically, but stays put, it is “weathering”. Once the particle starts moving, it is “erosion”. Wind and water (waves, streams and rivers, and glaciers) are causes of erosion. The pounding of waves against the shoreline can create sea stacks, sea arches, and sea caves. Wind combined with loose rock and sand can grind the surfaces of rock. Glaciers are large masses of snow, ice, and rock debris that accumulate in great quantities and begin to flow outwards and downwards under the pressure of their own weight. As glaciers flow, it erodes the surface by abrasion. Sediment is transported by the glacier and deposited where the ice melts. Abrasion occurs when debris-rich ice slides over bedrock abrading it like sand paper on a block of wood. U-shaped valleys, cirques, and hanging valleys are some of the landforms created by glaciers.