Weathering and Deposition – Different Types

Weathering and deposition

Introduction:

Earth is the place where we live, and it is the third planet from the Sun. 70% of the Earth is covered by water. Earth is a unique planet. It has supported life for many years. Earth is round, and it is not a solid piece of rock. It is made up of various layers. Each layer of Earth has different physical and chemical characteristics.

Earth is also called a water planet or blue planet due to the presence of water on it. The only planet that has water on its surface is Earth. There are many features of the Earth’s surface. These features are called landforms. There are many factors, such as wind, water, chemicals, and depositions, that shape the land.

Every sedimentary rock on Earth is formed by weathering, erosion, and deposition.

Weathering is the formation of sediments caused by wind or water tearing off pieces of rock or by ice or biological activity (such as tree roots and animal hooves) breaking at a rock.

Erosion is the movement of these sediments from their point of origin to their final location via wind, water, or glacial ice.

Deposition is the process by which these sediments are deposited because of their mode of movement or erosion method (by glacial ice, wind, or water).

Weathering

Weathering is the breakdown of rocks and minerals on the surface of Earth. Weathering agents consist of water, ice, acids, salts, plants, animals, and temperature changes. After a rock has been broken down, the rock and mineral fragments are transported away by the process of erosion. There is no rock on Earth that is strong enough to resist the forces of weathering and erosion.

These processes, when combined, carved landmarks such as the Grand Canyon in the U.S. state of Arizona. This massive canyon stretches for 446 kilometers (277 miles), is as wide as 29 kilometers (18 miles), and is 1,600 meters (1 mile) deep. The rocky landscape of Earth is continuously changing because of weathering and erosion.

Weathering gradually erodes exposed surfaces. The length of exposure frequently influences how vulnerable a rock is to weather. Rocks that are suddenly buried underneath other rocks, like lavas, are less prone to weathering and erosion than rocks that are exposed to agents like wind and water.

Weathering is frequently the first step in the formation of soils because it smoothens rough, sharp rock surfaces. Plants, animal remains, fungi, bacteria, and other organisms coexist with weathered minerals. Weathered materials from a collection of rocks are richer in mineral diversity and contribute to more fertile soil than weathered materials from a single type of weathered rock.

Types of Weathering:

Weathering is divided into the following processes:

1. Mechanical weathering or physical weathering
2. Chemical weathering
3. Biological weathering

Mechanical Weathering:

Rocks crumble because of mechanical weathering, also known as physical weathering.

Temperature, pressure, frost, root action, and burrowing animals can all cause physical weathering.

Water: Whether liquid or solid, water is a common mechanical weathering agent. For example: Liquid water can percolate into cracks and gaps in the rock. Water will freeze if temperatures fall low enough. Water expands when it freezes.

The ice then functions as a wedge. It gradually enlarges the cracks and splits the rock. When ice melts, liquid water erodes by carrying away the tiny rock fragments that were lost in the split. This particular process (the freeze-thaw cycle) is referred to as frost weathering or cry fracturing.

Temperature variations can also add to mechanical weathering through a process called thermal stress. Temperature changes cause the rock to expand (with heat) and contract (with cold). The structure of the rock weakens as this occurs repeatedly. It crumbles over time.

Wind: Wind’s physical forces carve and remove the loose rocks. Wind forces carry small particles and rocks, which collide with the rocks and wear them away. The effects of wind on physical/mechanical weathering are common in desert sandstorms.

Release of Pressure or Exfoliation:

When the overlying rock materials are stripped away by abrasion or other erosion processes, the underlying rocks crack, fracture, and expand parallel to the surface. This causes the underlying rocks to release pressure.

Exfoliation occurs when sheets of rock separate from the stripped rocks and break into smaller pieces along with the fractures over time. Exfoliation occurs when cracks form parallel to the land surface because of pressure release during abrasion, glacier retreat, or rock uplifts.

Plants and Animals:

Mechanical weathering agents include plants and animals. A tree seed may germinate in soil that has accumulated in a cracked rock. As the roots spread, the cracks widen, ultimately breaking the rock into fragments. Even large rocks can be broken apart by trees over time. Even small plants, like mosses, can grow and develop tiny cracks.

Weathering of rocks is also caused by animals. Burrowing animals such as ants, worms, moles, and rabbits dig the soil and bring rock pieces to the upper surface of the land and expose them for weathering.

Chemical Weathering:

The molecular structure of rocks and soil is altered by chemical weathering. For example, carbonation occurs when carbon dioxide from the air or soil combines with water. This produces carbonic acid, a weak acid that can dissolve rock. Carbonic acid dissolves limestone particularly well.

When carbonic acid seeps underground through limestone, it can open massive cracks or hollow out vast networks of caves. Carlsbad Caverns National Park in the United States state of New Mexico contains over 119 limestone caves formed by weathering and erosion.

Chemical weathering occurs in iron-containing rocks. These rocks rust due to a process known as oxidation. Rust is a compound formed when oxygen and iron react in the presence of water. Rust weakens and helps break up rock as it expands.

When CO₂ (carbon dioxide) present in the air gets dissolved in rainwater, a chemical reaction takes place, and carbonic acid forms. It is a weak acid that reacts with limestone. If water with carbonic acid gets percolated into the ground that consists of limestone, then the limestone dissolves in the water and gets carried away by the flow of water. Over a period, eventually, this process forms a cavern.

Biological Weathering:

Both processes can include biological weathering, in which living or once-living organisms contribute to weathering.

Erosion and Deposition:

Erosion and deposition are processes that alter the appearance of the Earth’s surface over time. Both are natural and continuous geological processes that produce relief features on the Earth’s surface. The movement begins with erosion and ends with deposition.

Erosion:

The means of eroding or being eroded by external agents like wind, water, or other natural agents is known as erosion. This process has the potential to dissolve rock, weakening it or fracturing it into tiny fragments. Erosion is the movement of rock or soil from one location to another.

Climate (the frequency, intensity, and duration of rainfall, as well as the size of the area on which the rain falls, are key factors in determining the amount of runoff), vegetative cover, and soil type are all factors that influence the erosion process.

The Four Main Types of Erosions are as Follows:

1. Abrasion: Abrasion occurs when pebbles grind against the riverbank and bed, creating a sandpaper effect.
2. Hydraulic action: It is the sheer force of the water as it slams against the riverbanks. Air becomes trapped in the riverbank, and the bed cracks, causing the rock to break apart.
3. Solution: When seawater dissolves certain rock types, this is referred to as a solution.
4. Attrition: Attrition occurs when the sea transports the rocks, and these rocks collide. As a result, they disintegrate, becoming more rounded and smaller.

Water Erosion:

The most important natural erosional agent is moving water. Coastal erosion is caused primarily by the action of sea waves, but it is also caused in part by the disintegration or degradation of sea cliffs caused by atmospheric agents such as rain, frost, and tidal scour.

Hydraulic pressure, the impact of waves striking the shore, and abrasion (wearing, grinding, or rubbing away by friction) by sand and pebbles agitated incessantly by the water are the primary causes of sea wave erosion (see wave-cut platform). Wave impact and hydraulic action are typically the most damaging to man-made coastal features like breakwaters and moles.

The wave action drags particles back and forth, rubbing the bedrock along the coast and rubbing each other, gradually wearing pebbles into sand.

Sediments are transported by the lateral movement of waves after they wash ashore (beach drifting) or by shallow-water transport just offshore, known as longshore currents, in addition to the back-and-forth transport of materials by wave action. These transportation movements result in deposition and the formation of prograde (advancing) shorelines, bars, spits, bayhead beaches (formed between two headlands), and barrier beaches (a barrier beach parallels the shore).

Glacial Erosion:

Glacial erosion occurs in two ways: abrasion of surface materials as the ice grinds over the ground (much of the abrasive action is due to debris embedded in the ice along its base) and quarrying or plucking rock from the glacier bed. The eroded material is transported until it is deposited or the glacier melts, whichever comes first.

Wind Erosion:

The wind has a significant impact on the erosion of rocks in some arid and desert areas by driving sand, and the surface of sand dunes that are not held together and protected by vegetation is subject to erosion and change due to the drifting of blown sand.

This action erodes material through deflation (the removal of small loose particles) and sandblasting of landforms caused by wind-transported material. Deflation of loose particles from landforms continues, leaving behind larger particles that are less susceptible to deflation.

Wind action transports eroded material above or along the Earth’s surface via turbulent flow (in which particles move in all directions) or laminar flow (in which particles move in only one direction) (in which adjacent sheets of air slip past one another).

Deposition:

Deposition occurs when whatever is transporting sediments can no longer hold them. Wind and water can slow and lose their ability to transport larger sediments that require a lot of energy to hold. When the wind and water cease to move, they can no longer carry any sediments and drop the last of what they are carrying! Water moves more slowly on shallower slopes, such as the valley floors of mountains.

Wind can cause a slowdown as it approaches taller objects, such as mountains or buildings. As the ice melts, glaciers deposit sediments. Layers of sedimentary rock formed from these sediments. After compacting, sedimentary rocks will form! Beaches exist because sand has been deposited in them!