Weathering

Weathering

It causes disintegration of soil

Mechanical Weathering

Exfoliation

Physical Weathering

Organic Weathering

Hydration

Mechanical Weathering

Chemical weathering

Constructive forces

Block Disintegration

Polar climates

Both A and R are true and R is the correct explanation of A.

Explanation — Weathering is described as disintegration or decomposition of a rock in size by natural agents at or near the surface of the earth. The disintegration or decomposition of rocks take place only by being exposed to changes in weather conditions like temperature, moisture, precipitation that disintegrate or break down the rocks.

C

Chemical

Weathering is the process of breaking down of rocks but not its removal. It is described as disintegration or decomposition of a rock in size by natural agents at or near the surface of the earth.

Three types of weathering are-

1. Physical weathering
2. Chemical weathering
3. Biological weathering

When the outer layers of rocks become loose and peel off or disintegrate from the main rock, it is called exfoliation. Sudden temperature changes may cause fissures into which water penetrates which in turn stimulates chemical weathering. The sudden contraction and expansion of rocks also causes exfoliation.

The processes involved in exfoliation are mechanical or physical weathering, chemical weathering, contraction and expansion of rocks.

The four processes involved in chemical weathering are-

1. Oxidation
2. Carbonation
3. Hydration
4. Solution

Oxidation means reaction of minerals in rocks to atmospheric oxygen.

When the atmospheric oxygen comes in contact with iron-compounds in rocks, the iron starts rusting or crumbling. The colour of the rock changes to red, yellow or brown.

Weathering is the process of breaking down of rocks but not its removal. It is described as disintegration or decomposition of a rock in size by natural agents at or near the surface of the earth.

The chief characteristics of weathering are-

1. It involves disintegration or decay of solid rocks.
2. It depends on climatic elements and on the characteristics of rocks.
3. It affects the surface of the earth.
4. It causes formation of soil.
5. It involves not one but several processes to cause disintegration of rocks.
6. It changes hard massive rocks into finer materials.
7. It prepares rock materials for transportation by agents of gradation.

(i) Physical weathering is also called mechanical weathering as it involves rock disintegration without any change in the chemical constituents of the rock.

(ii) Physical weathering is more rapid in desert climates because temperature changes are sharpest in a desert.

(iii) Chemical weathering occurs in moist and cold climates because such climate has abundant water and oxygen which are the main agents of chemical weathering.

Below diagram shows the process of physical weathering:

In chemical weathering, some or all of the minerals in the rocks suffer decay or alteration, by such agents as water, oxygen, carbon or various organic acids, and transform into different chemical combinations.

Four main processes involved in chemical weathering are-

1. Oxidation
2. Carbonation
3. Hydration
4. Solution

Biological weathering involves both physical disintegration and chemical decomposition as all biological matter is made up of oxygen and water.

The main agents of biological weathering are animals, insects, plants and man.

(i) Biological weathering is also known as organic weathering because it is the disintegration of rocks as a result of the action by living organisms.

(ii) Vegetation prevents disintegration of rocks because it binds the surface layer and does not allow exposure of rocks beneath to the elements of weathering.

(iii) Chemical and biological weathering is negligible in polar climates because water is in frozen state in the polar regions and most living organisms cannot survive in such cold climatic conditions.

The chief characteristics of weathering in different climates are-

1. In equatorial climates, humidity and temperature are constantly high. Weathering specially chemical weathering is more active in these regions.
2. In Tropical climates, there is a marked dry season and wet season. Differences in heating leads to consistently high rate of evaporation, During wet season, precipitation of oxides of iron and aluminium takes place from rocks. This promotes formation of laterite soils.
3. In dry climates or deserts, mechanical weathering is most dominant due to high diurnal range of temperature.
4. In mid-latitudes or temperate climates, the most powerful agent of weathering is the frost action. In limestone areas, solution or chemical weathering operates on a large scale.
5. In polar climates, physical weathering due to frost action is most prevalent. Chemical and biological weathering is negligible.

Yes, I agree with the statement that weathering is a natural process, but human activities can speed it up in the following ways:

1. Human activities like mining, quarrying, deforestation, construction, and agriculture cause weathering and disintegration of rocks.
2. Mining and quarrying activities involve explosions and the removal of large quantities of rocks and soil, which speeds up weathering.
3. Construction activities involve the removal of natural materials like rocks and soil, leading to increased exposure of the underlying materials to weathering agents.
4. Agricultural activities like tilling, irrigation, and use of fertilizers and pesticides also speed up weathering.

Therefore, while weathering is a natural process, human activities can cause it to occur at a faster rate, which can have negative impacts on the environment and ecosystems.

The statement that weathering is responsible for biodiversity on Earth can be justified by considering the crucial role weathering processes play in creating and sustaining diverse habitats. Weathering is a fundamental geological process that interacts with other factors, such as climate, topography, and biological activity, to shape the environment and promote biodiversity. Here are a few examples to support this justification:

1. Soil Formation — Weathering processes break down rocks into smaller particles, contributing to the formation of soil. The diversity of soil types and compositions resulting from weathering influences the types of vegetation that can grow in a particular area. Various plant species, in turn, support a wide range of animal species, including insects, birds, mammals, and microorganisms, creating a diverse ecosystem.
2. Erosion and Landforms — Weathering, combined with erosion by water, wind, or ice, sculpts the Earth's surface, leading to the formation of diverse landforms. Mountains, valleys, canyons, plateaus, and coastal cliffs are all products of weathering and erosion processes over millions of years. These distinct landforms provide diverse habitats for a wide array of species, allowing for the coexistence of different plants, animals, and microorganisms adapted to specific environmental conditions.
3. Nutrient Cycling — Chemical weathering breaks down minerals in rocks, releasing essential nutrients into the environment. These nutrients, including phosphorus, potassium, and calcium, are vital for the growth and survival of organisms. This nutrient cycling sustains the intricate web of interactions and relationships among various organisms, contributing to biodiversity.
4. Weathering and Water Bodies — Weathering processes also affect aquatic ecosystems. Weathering of rocks on land introduces minerals and sediments into rivers, lakes, and oceans. These minerals and sediments influence the chemical composition and turbidity of water bodies. These factors, along with temperature variations caused by weathering-related factors, create diverse aquatic habitats suitable for different species of fish, amphibians, aquatic plants, and microorganisms.
5. Climate Regulation — Weathering plays a role in regulating climate over long timescales. Certain types of weathering, such as the carbonation of rocks, absorb carbon dioxide (CO2) from the atmosphere, acting as a natural carbon sink. This process helps in mitigating the greenhouse effect and maintaining stable climatic conditions. Stable climates provide a more predictable environment for species, allowing for the development and maintenance of complex ecosystems.

I went to the Rann of Kutch for the Rann Utsav, which is celebrated annually in Gujarat. On my way, I noticed mechanical or physical weathering of rocks.

Rann of Kutch experiences desert type of climate i.e., very hot during the day and cold during the night. The sudden rise and fall of temperature causes expansion and contraction of rocks. The repeated action causes their breakdown. At night the temperature suddenly falls and during the day it rises suddenly. This leads to tension and splitting of rocks and block disintegration of rocks.

Most rocks are not good conductors of heat. The sudden contraction and expansion peels off the outer layer of the rock, which is known as exfoliation.