Weathering breaks down rocks and minerals on Earth’s surface. Erosion happens when these chemically and mechanically soft pieces of rock get transported away and deposited somewhere else.
These processes form part of an ancient geologic cycle and have been going on for billions of years.
Mechanical weathering erodes rocks into smaller and smaller particles, and gravity pulls these pieces of rock and soil downward. This movement is known as deposition; whether weathered materials are close by or far off on another continent.
Weather-weathered material often travels slowly through time, such as that which formed the Grand Canyon over thousands or millions of years. But sometimes erosion happens more rapidly, for instance during landslides and avalanches.
These events may be caused by natural or human activities. Examples include logging and farming – the vibrations caused by these activities often erode rocks; chemical weathering like carbonation breaks down igneous and sedimentary rocks to produce residual materials like gravel, sand, silt which are then deposited by gravity at the base of slopes (talus scree). Mass wasting is another rapid form of erosion which can dramatically reshape landscapes.
Weathering, erosion and deposition combine to continuously shape Earth’s landscape over billions of years – this continuous cycle has been called The Geologic Cycle.
Water is an integral component of weathering and erosion processes. Whether in the form of rain, ice or ocean waves, it plays a key role in weathering and erosion processes. Water seeping into cracks in rocks acts as a wedge wedge to split it, leading to pothole repairs in our roads and sidewalks frequently needed repairs; while expanding ice cracks also cause rocks to split open when expanding in an opening between stones.
Chemical weathering is more prevalent in areas with an abundance of water due to its ability to accelerate chemical reactions. For instance, water can react with iron in rocks to make them rust or mix with carbon dioxide from air pollution to form acid rain that weathers rocks more readily. Furthermore, water plays an integral part in erosion by carrying away softened or worn down rock layers that have become exposed over time.
Under freezing temperatures, freezing water penetrates cracks and crevices in rocks to cause them to expand and fracture, known as pressure weathering. This type of weathering is responsible for road potholes but also allows plants to flourish in some locations by encouraging moss, lichen, and ivy to take hold on buildings while creating hoodoos or arches in desert landscapes.
Ice plays an essential part in mechanical weathering by pushing and scraping against rocks it comes into contact with, known as abrasion. Glaciers also contribute to mechanical weathering by transporting rock and sediment from their valley walls into moraines; plucking rocks from their surfaces is then used to deposit these masses elsewhere as glacial till.
All these processes combine to form soil, which consists of water, minerals, and organic matter that supports living things such as plants, fungi and other organisms that use this organic matter for exchanging nutrients with their roots.
Erosion is the process by which weathered rocks become loose and transported across landscapes by wind, running water, waves, glaciers or underground water sources. Erosion’s transportation element allows weathered rocks to move to new areas where further weathering can take place.
Wind is a potent erosion force. It can transport dust, sand and ash between locations while simultaneously scourring and polishing rock surfaces – sometimes creating beautiful shapes like Arches National Park in Utah’s stone arches!
Wind erosion can leave sediment deposits behind as it travels with winds, running water, glaciers or other natural processes – leaving behind deposits such as deltas, beaches or loess deposits (a type of rich soil). Human activities can accelerate weathering and erosion processes as well – for instance burning coal, natural gas or petroleum releases chemicals into the atmosphere that combine with water and sunlight to form acids which weather limestone and marble surfaces over time.