1. Weathering: This is the process that breaks down rocks at or near the Earth's surface. It can be categorized into two main types:
* Physical Weathering: This involves the mechanical breakdown of rocks without changing their chemical composition. Examples include:
* Frost wedging: Water seeps into cracks, freezes, expands, and widens the cracks.
* Thermal expansion and contraction: Temperature fluctuations cause rocks to expand and contract, leading to cracks and fragmentation.
* Abrasion: Rocks rub against each other, causing wear and tear.
* Biological weathering: Plant roots, burrowing animals, and lichens can break down rocks.
* Chemical Weathering: This involves the chemical alteration of rocks, changing their composition. Examples include:
* Dissolution: Acids in rainwater dissolve certain minerals in rocks.
* Oxidation: Oxygen reacts with minerals, changing their composition.
* Hydrolysis: Water reacts with minerals, breaking them down.
2. Erosion: This is the process of transporting weathered rock fragments from one location to another. It is driven by various forces, including:
* Wind: Wind can pick up and transport small rock particles, creating sand dunes and other wind-blown features.
* Water: Rivers, streams, and waves can erode rocks and transport sediments.
* Gravity: Gravity pulls rocks down slopes, leading to landslides, rock falls, and other forms of mass wasting.
* Glaciers: Glaciers can carve valleys, transport boulders, and deposit glacial till.
3. Deposition: This is the process where eroded sediments are dropped or settled in a new location. This can occur when the transporting force loses energy, such as:
* Rivers: Rivers deposit sediments as they slow down or enter a lake or ocean.
* Wind: Wind deposits sediments in areas with less wind energy, creating sand dunes or loess deposits.
* Glaciers: Glaciers deposit sediments as they melt, creating moraines and outwash plains.
* Oceans: Waves and currents deposit sediments along coastlines, creating beaches and sandbars.
These external forces are constantly at work, shaping the Earth's surface and driving the rock cycle. They break down existing rocks, transport the fragments, and ultimately contribute to the formation of new rocks.
