Question

After studying this Module 8, answer the following questions in this Journal:

Briefly explain why water is such an important agent in chemical weathering.

How do soils that form in humid regions differ from soils that form in semi-arid regions in the environments in which they form and in their basic characteristics?

Explain why and give two examples of how climate is more effective in determining soil type than is parent rock type.

How does gravity affect a slope?

What is the angle of repose for a slope? What forces are acting? What numerical value does this angle have?

Answer 1

Why water is such an agent in chemical weathering

Weather is a process that takes place slowly over a period of time. It is responsible for altering rocks, to something that is somewhat more stable. Water is one of the main agents of weathering. As a matter of fact, no rock is considered as most stable that it can resistant weathering process.

Now when speaking of chemical weathering, this is a process that takes place in the part of the soil that has a consistent percentage of mineral and water. So water is one of the most important agents for chemical weathering.

• One of the first ways in this process is that water will easily combine with the Carbon dioxide that is present in the rock or soil. Due to this process, the formation of weak acid takes place which is also called carbonic acid.
• Then there are also microorganisms that generate in the soil or rock that has an abundance of Carbon Dioxide percentage.
• Minerals that are in the rock will easily get dissolved because of the Carbonic acid. It will transform the rock into something that is also water-soluble, whereas all minerals that are hard will get mixed with the water and make it “hard water”.
• Secondly, as a part of the weathering process, minerals can easily get hydrated by water and change in latticed form – eg. Gypsum.
• By the process of hydrolysis, it is also possible that water breaks down the original contents of the minerals. During this process, minerals may also get decomposed by the action of water.

Difference between soils in humid and semi-arid regions

Now you have to keep in mind that humid itself represents the presence of water. When speaking of soil formed in the humid region, here the soils are considered to be present in the depth. The soil in this region also undergoes the strong process of weathering.

So the conditions under which the soil is formed are harsh. The climate conditions here are also moist and warm, within the soil. Here in this region, the soil is continuously undergoing weathering stage. So the temperature of the soil is much higher here and average months means of temperature can be around 22 Deg. C.

The moisture content of the soil is also maintained the same for year-round.

Semi-arid region soil is continuously exposed to rainfall like conditions. This is one of the reasons that also explains the homogenizing effect. The soil is highly productive as the vegetative cover in this region is much higher in percentage.

At areas, you may also get to notice the surface horizons and the soil in this region is also considered to be rich and made up of most organic matters. So in this type of soil, you may hardly find regions that are desert-like pavements, efflorescence and vasicular horizons.

Effects of climate on soil type

Now you need to keep in mind that soil formation is a process that may take thousands of years. So it takes a few thousands of years for the soil to form, such that it can support life. Climate is considered as an important element that can affect the formation process of the soil.

Changes in climate will also result in changes in the soil formation process. Apart from this, climate also affects the soil usage and development process. It is directly responsible for affecting the nutrient contents and percentage of the soil particles.

The climate effect can also alter the vegetation coverage of the soil as it can decrease or increase its vegetation coverage. Carbon inputs will affect the quality of soil as the process of organic matter turnover to form soil will get directly affected. So if the soil is getting rich carbon then the percentage of the organic matter also increases, and the soil gets more productive.

Apart from this, the soil quality is also affected by global climate changes, rainfall percentage, nitrogen percentage and other elements of climate.

Effect of gravity on a slope

Gravity is one of the forces that pulls the object (soils- as in this case), down the slope. The particles that are on the higher elevation will have less effect of gravity, as compared to particles that are near to the ground on the slope.

As we are already aware of the gravity factor in physics that Gravity is maximum at the ground level but with an increase in height the gravity decreases.

The angle of repose and its value

The angle of repose is also termed as the critical slope angle. This is also the steepest possible angle of dip or descent for the granular particle as relative to the horizontal plane. So this is the angle that any granular particle present on the slope has to face.

So now if we have to speak of the values of this angle, it can have any possible value that may range from 0 Deg. and 90 deg.

The value to exceed above 90 Deg may not be possible as it would be against the laws of gravity.