Weathering and erosion have long been shaping Earth’s landscape by gradually chipping away at rocks and sediment deposits, shaping landforms such as fan-shaped deposits in deltas.
Weathering is the process of breaking down rocks and minerals while erosion transports these fragments through rivers to be deposited as new land mass – known as deposition.
Weathering
Weathering, which refers to the gradual breakdown of rocks and minerals on or near Earth’s surface through physical, chemical and biological processes, can occur either gradually or quickly depending on factors like temperature, climate and type of rock present. This process is determined by temperature, climate and rock type among others.
Chemical weathering refers to the breakdown of rock by chemical agents such as oxygen or water. Oxygen can oxidize iron to form rust while water can alter feldspar into clay minerals.
Mechanical weathering occurs when rocks disintegrate through physical means like abrasion or impact, for instance when sharp-edged rocks hit against each other or were washed ashore by waves. Plant roots can also contribute to mechanical weathering by growing into cracks and wedged open by waves; while burrowing animals may also break apart rocks.
Biological weathering refers to the dissolution of rocks and minerals by living organisms, such as fungi or lichens that live on rocks and gradually consume them over time. Temperature and moisture are also major influences; higher temperatures accelerate chemical weathering of rocks.
Erosion
Water is one of the most powerful tools of nature for altering landscapes, as its flow across rocks and sand wears them away, creating erosion. Erosion refers to the transportation of weathered rock particles by natural processes like wind, water, ice, gravity or any combination thereof – and any deposition as a result is known as sedimentation.
Erosion causes various kinds of landforms to form, from gullies and streams to desert dunes. Aeolian (wind-driven) erosion transports dust and other materials from one location to the next until eventually depositing them as towering dunes like those seen in Badain Jaran section of Gobi Desert in China.
Water erosion is responsible for creating smooth rock formations found in many canyons and rivers as well as arches found at Arches National Park in Utah. When water erodes rocks or soil particles it transports them downstream as sediment called silt that settles.
Deposition
Weathering of rock reduces it into sediments like sand and pebbles that can be transported by erosion. When this process loses energy to carry the materials far enough away from their source (wind, glacial ice or water), they fall off at their new destination in what’s called deposition; this process creates low lying areas such as deltas or can be carried off mountain sides by rivers to form features like rocky river beds in mountains or ox bow lakes on plains.
Erosion-deposited material can carry harmful substances such as chemicals, fertilizers and pesticides that pollute our freshwaterways – an additional reason to control erosion rates and limit deposition and erosion rates as much as possible.
Deltas
Deltas form when river sediment supply exceeds removal by waves and tide currents, creating an imbalance. They’re usually triangular in shape and named for resembling Greek capital letter delta; when this happens when rivers enter seas, lakes, estuaries or reservoirs that cannot carry away all their deposits they deposit a delta is created.
The lower delta plain, as seen on satellite images, is dominated by marine processes and periodically inundated by tidewater floods; between channels exist broad freshwater marshes or swamps which support freshwater life.
Cuspate deltas (shaped like bird feet) involve foreset beds being deposited layered, inclined layers over existing bottomset beds as the active delta lobe advances. Foreset beds typically display larger, more variable particle sizes. Tectonic stability and river slopes also play a part in controlling delta development resulting in an incredible variety of landforms created by deltaic development.