Weathering refers to the breakdown of rocks and minerals on Earth’s surface; erosion refers to their removal.
Weathering and erosion are everywhere we look; from road splits to blackened beaches. Weather, wind, ice, gravity are the driving forces responsible.
Weathering
Weathering is the process by which rocks and minerals break down into smaller pieces through various means: heating and cooling cycles, frost wedging, impact of rocks against each other (abrasion), chemical changes caused by acid rain or oxygen and more.
After rocks have been broken apart, erosion transports their fragments away and deposits them elsewhere. This process may occur slowly over time like riverbank erosion or quickly through mudslides.
Water is responsible for most erosion on Earth, though wind, running water, and glacier movement can also have an impact. Plants and animals can act as agents of mechanical weathering by way of roots entering cracks in rocks to open them up, while animals burrow underground breaking apart rocks as they travel; others dig and trample aboveground breaking apart rocks into pieces that form hills and plains over time. Together these forces can turn smooth roads into rutted ones or transform tall mountains into hills and plains over time.
Erosion
Erosion is a natural process which involves moving weathered rock particles from one location to another over time, driven by water, wind and gravity. Erosion is what forms cracks and splits in rocks as it wears away over time and turns cliffs into canyons.
Erosion occurs through waves crashing upon beaches and through the wind blowing dust and sand from one area to the next, as well as through slowly wearing away at rock in streams and rivers, or quickly through mudslides.
Chemical weathering — which includes oxidation, hydrolysis and carbonation — breaks down rocks by dissolving their bonds with each other, making the rock easier to break apart in water or wind, leading to its transport across larger distances. Plant roots help slow erosion by holding soil particles together through glue-like glueing action; hence landslides tend to occur more frequently in areas with little vegetation cover such as those cleared for agriculture or urban development that plow land for plowing purposes or use. Deforestation contributes further erosion along with deforestation as does plowing land clearing or plowing land being ploughed for agriculture or urban development plowed land being ploughed for urban development contributing further erosion rates.
Deposition
Geological processes continue to contribute sediments such as pebbles, sand and silt to Earth’s surface through processes like wind, ice and gravity. Wind can carry away previously eroded material that will eventually settle as layers of sediment; but flowing water or the sea may also deposit layers of sediments as layers.
Transport of sediment particles may lead to their edges becoming rounded; this information provides geologists with a window into how much material was moved over a specific distance and over how long. They use it to read into rocks what tales may lie hidden therein.
Rounding can also serve as an indicator of the type of erosion that occurred, with windblown sand being particularly well sorted compared to glacial deposits that are typically not. Mineral content and force of transporting agents provide further indicators as to what type of weathering occurred, providing geologists with vital data needed for stratigraphy (interpreting past climate histories recorded in rocks).
Soil
Soil erosion threatens agricultural productivity, degrades ecosystem functions and amplifies hydrogeological risks like landslides or floods, reduces biodiversity and damages urban infrastructure – all major threats to global food security and achieving the Sustainable Development Goals set by the UN.
Physical weathering – which causes cracks, nicks and chips in rock and soil – is caused by temperature, pressure, frost, root action of trees roots or burrowing animals like moles. Mechanical weathering agents include plants like mosses and lichens which have root systems capable of widening existing cracks in rocks through root action.
Chemical weathering is caused by the combined action of fungi, bacteria and water; their acids erode rocks and soil by dissolving minerals. Climate also plays an important role as extreme variations in rainfall or temperature can shift soil layers; additionally wind can also play an integral part in either mechanical or chemical weathering processes.