Nature’s forces are constantly at work altering Earth’s rocky terrain. Weathering and erosion are two processes which sculpt rock into ever-evolving works of art.
Once completed, tiny bits of rock will be carried away by erosion and deposited elsewhere through deposition – this process helps shape our world.
Physical
Weathering of rocks impacts soil development and texture, releases chemical compounds for biological processes, influences atmospheric chemistry and temperature and impacts atmospheric temperatures and pressures. Physical disintegration leads to erosion – the movement of sediments (such as gravel or sand ) across different sites via water currents, wind forces or glacial ice movement; which has multiple downstream effects that influence human lives and environments.
Breakdown of rocks is caused by many different forces, including freeze-thaw cycles and thermal expansion. Some forms of weathering reduce rocks without altering their chemical makeup, while other methods alter its physical structure.
Erosion affects Earth’s surface in various ways, from pebbles grinding against riverbanks or beds, wave action churning rocks into sand along a coast, grinding rock materials in fast-flowing streams, to shattering rocks by freezing water expanding as ice.
Chemical
Submersion in water alters the molecular structure of rocks. Carbon dioxide from air and soil sources combines with water to form weak acid that dissolves rock; this process is known as chemical weathering.
This process can also create unusual landscapes, like those seen at Bryce Canyon National Park in Utah’s hoodoos. Water can also use this process to grind rocks into sand as it flows over and through a valley, while wave action breaks up sediment on beaches or shorelines and deposits it there.
Mechanical weathering is often caused by plant activity or other forms of organic life, like tree roots entering cracks in rocks to slowly break them apart. Liquid water seeping into cracks then freezing and expanding is also known as frost weathering or cryofracturing, another popular mechanical weathering technique.
Biological
Weathering and erosion continuously alter the Earth’s landscape. Deposition occurs when whatever was transporting sediment no longer has enough energy to carry it – such as wind, water, glaciers or living organisms – leading to its deposition elsewhere.
Mechanical weathering breaks rocks and sediment down into smaller fragments by various natural forces such as floodwaters scour rock in stream valleys or waves erode cliff faces along beaches, or by freezing-thawing cycles that act like wedges splitting rocks apart through frost weathering processes. Root action, burrowing animals and other organic activities are also often responsible for mechanical weathering processes.
Chemical weathering can drastically change the texture and chemical makeup of rocks. Acid rain, with its high concentrations of nitric and sulfuric acids, can turn rock to rust while its acids can also eat away at minerals’ surfaces, leaving them dull and scratchy.
Human
As humans construct cities, farms, highways and mining operations on Earth’s surface, we alter its landscape at an unprecedented speed. Humanity’s creation of cities, farms, highways and mining operations alters Earth’s surface more quickly than any natural cause ever could.
Rocks typically live their entire lives underground, where conditions tend to remain relatively constant, pressure is high, and contact with the atmosphere is limited. Once exposed at the surface however, they become susceptible to weathering and erosion forces that threaten their existence.
Water in streams and rivers and glaciers plays an essential role in erosion by transporting away rock debris and washing away any chemically weathered materials that might build up.
Biological weathering is another critical physical process. Roots from plants sometimes make their way into rocks, causing erosion and cracks in them to widen until eventually, they crumble away altogether.
Wind is another powerful agent of erosion. It transports dust and other materials across long distances, contributing to Arches National Park in Utah’s unique shape as well as Baffin Island’s Admiralty Inlet’s signature arches.