Dialogue Discussing the process of erosion

Prof. Smirnov:

Student:

Prof. Smirnov:

Student:

Prof. Smirnov:

Student:

Prof. Smirnov:

Today we are going to consider the following questions: erosion, weathering (chemical and mechanical weathering).

Will you explain what the term “erosion” means?

All the processes by which rocks are worn down and by which the debris is carried away are included in the general term “erosion”. There exists one more term – “gradation”. You learnt about it at the previous seminar.

Yes, we know that the leveling of landscape by erosion is often referred to as “gradation”.

During our practice we saw the rough, pitted surfaces of old stone monuments and buildings. Such sort of disintegration brought about by rainwater and atmospheric gases is called weathering. But what are the active erosional agents?

Weathering is in part a chemical process, in part a mechanical process. It participates in erosion in an important way by preparing rock material for easy removal by the more active erosional agents. Among the agents whose work is most obvious are streams, glaciers, wind and waves. Less apparent is the erosional work of groundwater, water in crevices and channels beneath the surface. I’d like to know whether you have got any information concerning chemical weathering. What is easily attacked by chemical weathering?

Some of the minerals in igneous and metamorphic rocks are especially susceptible to chemical weathering. most sedimentary rocks, on the other hand, consist of rock debris that has already undergone chemical weathering, and so are relatively resistant to further attack; the chief exception is limestone.

As for mechanical weathering the most effective process of mechanical disintegration that does not involve chemical action is the freezing of water in crevices, since water expands when it turns into ice and considerable forces can be developed in this way. Plant roots aid in rock disintegration by growing and enlarging themselves in cracks.

In conclusion I’d like to say that the upper part of the weathered layer, in which rocks debris is mixed with decaying vegetable matter, is the soil. And from a human point of view the formation of soil is the most important result of weathering.