Weathering erosion deposition (WED) is the process of gradually breaking down and rebuilding Earth’s surface over time. This includes taking into account climate, topography and vegetation as factors in this cycle.
Physical and chemical weathering break rocks down into smaller pieces that are then easily transported and deposited by water, wind or gravity.
Physical erosion involves breaking rock into small particles and transporting those particles across landscapes – this process shaped many spectacular environments on Earth, such as the Grand Canyon which was created over millions of years by flowing water.
Physical erosion occurs through both freeze-thaw cycles and plant root growth. Freezing and thawing water expands and contracts rock cracks, loosening chunks that can then be broken off at the surface. Plant roots also gradually widen cracks over time to achieve this same goal.
Wind erosion is another key force in erosion. Its force can transport dust and sand across landscapes, polishing rock surfaces, polishing sand dunes like those at Badain Jaran in China and shaping features like those found at Scotts Bluff National Monument’s mushroom-shaped limestone and sandstone formations, or eroding soft rocks like Scotts Bluff National Monument’s soft limestone formations – not to mention carrying clay particles and silt that make up soils!
Water can erode rocks as it flows across a landscape. This process, known as chemical weathering, may occur quickly in a river setting or over longer time periods due to reactions between chemicals in water and minerals found within rocks – including oxidation (reacting with oxygen), hydrolysis (interacting with water) and carbonation ( reacting with carbon dioxide).
The rate at which these chemical reactions take place depends on both temperature and climate conditions; permeable rocks (rocks with holes) typically weather faster than impermeable ones. Lichens, fungi and algae that grow on rocks produce weak acids that chemically weather rocks more rapidly; acid rain also produces rapid chemical weathering that often forms caves or sinkholes where groundwater contains acidity; ice also plays a part when freezing expands inside cracks in rocks causing chemical erosion.
Since Earth began, wind has been shaping its landscape. Wind erosion refers to the movement of small pieces of rock and soil from one location to another due to rain, ice, plants, gravity, or temperature variations.
Most weathering is a slow process, but sometimes rapid weathering occurs. Water can quickly erode rocks by cracking them apart. Ice may wedge itself between cracks in rocks and split them open further; and plants may grow in these openings to wear away at them gradually.
Wind can also carry particles across landscapes, creating sand dunes and polishing rocks and cliffs until they appear smooth (a process known as desert varnish). Research indicates that oil and gas pad activity contributes to regional dust risks through erosion (Belnap et al. 2009); national-scale monitoring programs can assess this impact; rates of dust production on and off pads will likely differ, necessitating more research.
Many of us witness erosion daily: water seeping through cracks in rocks and sidewalks wears away rock to form sand, while wind can wear away pieces over time and carry them to new places, sometimes creating fantastic landscapes such as mushrooms growing out of rocks.
Glaciers can erode the land too. Glaciers scour across its surface, moving rocks and sediments around before depositing them elsewhere before melting begins – creating some fascinating landforms such as horns, moraine hills and U-shaped valleys in their wake. This process is known as glacial erosion.
Ice erosion may be slow-going, but when it does happen it can profoundly alter the landscape. Ice scraped against rock surfaces can wear away at their surfaces through abrasion or cause striations marks similar to what you would get by using sandpaper on wood pieces; creating distinct characteristics known as “roche moutonnees and aretes”.