Weathering and Erosion


Staff member
Jun 3, 2020
Weathering and erosion are the processes responsible for disintegration, transportation, and deposition of rocks. These processes occur when the rocks are exposed to atmosphere and biosphere.

Weathering is a process of weakening and dissolving rock minerals through physical, chemical, or biological agents.

Types of weathering
There are 3 main types of weathering:
  1. Mechanical weathering
  2. Chemical weathering
  3. Biological weathering
Mechanical weathering
Mechanical weathering is a physical change in the size of grain without chemical changing in their composition.

Exfoliation or onion skin weathering
When pressure release into rocks its disintegrates and peels away rock sheets. This type of weathering is common in warm areas. As the sun shines on rocks during the day it causes them to expand. During the night the rock contracts due to the colder temperature. Over time this continued process causes small pieces of surface rock to peel away.

Frost wedging or freeze-thaw action
This weathering caused by the freeze-thaw action of water. when water traps into the crack and when freeze, it expands and exerts pressure on the rock. This Action break and weak the rocks through repetitive action of the freeze-thaw weathering process.

Salt wedging
Most Waters contains dissolved salt. When the water in rock fissures evaporates, salt crystals form that, like ice, can force open fissures. As the salt crystal grows it exerts pressure on the rock, weakening it. until it eventually cracks and breaks down.

Rock Abrasion
Abrasion occurs when rocks collide with each other while they are transported by wind, water, glacial ice, or gravitational forces.

During abrasion, rock may also weather the bedrock surface when in contact with the bedrock surface as well as it breaks into smaller pieces.

Chemical weathering
Chemical weathering is decomposing, dissolve, alter and weak the rock through the chemical processes to form residual material.

The carbonation process is by which carbon dioxide and water or moisture from the surroundings react chemically to produce weak acids that react with carbonate rocks. It weak the rocks and removes chemically weathered materials.

Hydrolysis is a chemical process of H and OH ions in the water which react with rock minerals and produce weak acid. this reaction produces a weaker and soft compound than its original rock.

Oxidation occurs when oxygen and water react with iron-rich rock and weaken the rocks. during oxidation, the minerals in rock change their color to reddish rusty, orange color.

The solution occurs when water dissolves the rock minerals. the solution commonly occurs in carbonate rocks, but may also affect with a large amount of salt or, halite.

Biological weathering
Biological weathering is the disintegration or decay of the minerals of rock caused by physical or chemical agents of the organism.

Plant Roots
When roots of plant penetrate into rock cracks it exerts pressure on rock and causes the rock to split into pieces or is the most common biological weathering.

Organism activity
Small organisms burrow or tunnel into rock and cause the rock to disintegrate or break down. Snails, worms, and often other animals contribute to this process.

Some animals like snails, barnacles, or limpets, attach themselves to rock and secret acid, acids that chemically dissolve rock surface.

Lichen, Algae, and Decaying Plants
The biochemical weathering process leaches minerals from the rock and causes the rock to break down.

The decaying of plant material can also produce an acidic compound which dissolves the rock.

Erosion is a process that carries all rock particles, and deposits to other locations.

Types of erosion
  1. Water erosion
  2. Coastal Erosion
  3. River and Stream Erosion
  4. Wind Erosion
  5. Ice Erosion
Water erosion
when soil ends up being detached, removed, or washed away by water. It can be related to rainfall or running water, such as the movement of a significant quantity of melting snow. There are several examples of this type of erosion.

Splash erosion
Splash erosion occurs when raindrops hit bare soil. The explosive impact breaks up soil aggregates so that individual soil particles are ‘splashed’ onto the soil surface. The splashed particles can rise as high as 60cm above the ground and move up to 1.5 meters from the point of impact. The particles block the spaces between soil aggregates so that the soil forms a crust that reduces infiltration and increases runoff.

Sheet erosion
Also caused by rainfall, sheet erosion is a more severe form of erosion than splash erosion. It is the sheet-like washing away of loosened particles of soil. It is caused by runoff resulting from rainfall or a large quantity of melting snow. Sheet erosion commonly, but not always, occurs on land that has a slope.

Rill erosion
Rill erosion can be caused by rainfall or the movement of melting snow. Rather than soil washing away in sheets, rill erosion causes the water to cut through the soil, creating small channels on either side that measure no more than 3/10 of an inch in depth. These shallow flow paths through which rainwater flows are an example of rill erosion.

Gully erosion
Rill erosion can progress into gully erosion. When the water movement is powerful enough to increase the channels to larger gully pathways greater than 3/10 of an inch, that is when gully erosion occurs. This type of water erosion can be caused by rainfall or melting snow as it moves. It occurs in areas where runoff water accumulates and flows quickly.

Tunnel Erosion
Tunnel erosion is the most severe form of water erosion caused by rainfall or melting snow. With this type of erosion, water drips through a hole in the surface, removing soil underneath ground level and carving out a tunnel. It may not be obvious from the surface that there is a hollow area below, at least in the early days after a tunnel forms. Once a tunnel has been in place for a while, the soil on the surface will begin to give way on its own, if it has not already collapsed due to the weight being placed on it.

Coastal Erosion
Coastal erosion is caused by water, but it doesn’t result directly from rainfall. Instead, coastal erosion refers to the impact that wave action has on the shoreline of oceans, seas, and gulfs. As waves crash into land on the shore, the sand, rocks, cliffs, or soil along the shoreline gets eroded. Increases in sediment in the water greatly amplify the impact of coastal erosion.

River and Stream Erosion
Unlike oceans and gulfs, rivers and streams flow between the banks rather than producing crashing waves. River and stream erosion occurs as a result of the impact of moving water on the soil on either side of a flowing body of water. As water flows, the banks of streams, rivers, creeks, and other bodies of water can be worn away due to erosion.

Wind Erosion
Wind erosion is erosion caused by wind. It occurs when the wind picks up soil from one area, carries it a distance, and leaves it somewhere else. It can occur in locations that are windy a lot of the time, as well as places that only occasionally experience wind. The power of wind can move loose soil and also wear down surfaces due to particles carried in the wind.

Ice Erosion
Ice erosion is caused by the movement of glaciers, which are powerful ice formations. The most powerful examples of glacial erosion occurred long ago, during the Ice Age. There are still some places on earth (Greenland and Antarctica) where this phenomenon still occurs. Glaciers can cause erosion to occur as they move across land, picking up and displacing soil and anything else that they go over.
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