Discussing the process of erosion

Ex 1. Read the dialogue and reproduce it a) abridged; b) in the form of a monologue.

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.

Ex 2. Translate into English using the vocabulary of the dramatized dialogue.

Выветриванием называется совокупность процессов разрушения и химического изменения горных пород в условиях земной поверхности или вблизи нее под воздействием атмосферы, воды и организмов. Процессы выветривания подразделяются на два типа – физическое и химическое выветривание. Оба типа выветривания тесно связаны друг с другом и действуют совместно. Интенсивность проявления каждого из них определяется рядом факторов: климатом, составом пород, рельефом и т. д. В разных местах она неодинакова.

Физическое выветривание делят на температурное и механическое. Интенсивность температурного выветривания зависит от состава породы, ее строения, окраски и других факторов. Суточные колебания температуры при выветривании играют большую роль, чем сезонные.

Механическое выветривание происходит под воздействием таких факторов, как замерзание воды в трещинах и порах горных пород, кристаллизация солей при испарении воды, т. е. оно тесно связано с температурным выветриванием. Особенно сильный и быстрый механический разрушитель горных пород – вода. При ее замерзании в трещинах и порах горных пород возникает огромное давление. В результате его порода распадается на обломки. Это явление часто называют морозным выветриванием.

Listening Comprehension

Text “Continental drift”

Part A. Pre-listening activities

Task 1. Make sure that you know the following words and word phrases.

float v – плавать (на поверхности)

hard a – твердый

involve v – вовлекать

plate tectonics – тектоника

rigid a – жесткий

occur v – происходить

consequence n – последствие

stiff a – тугой, жесткий