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Unit II. Earthquakes.

Focus on:

• общенаучная и терминологическая лексика
• видо-временные формы глагола и их употребление
• построение дефиниций

 

Revision:

употребление:

· some/any/no

· most/a most/the most

· little/few/a few

· because/because of

· until/unless

· though/although/through

 

Text Study.

I

Seismic phenomena, or earthquakes, are the most terrible catastrophes occurring in nature. A strong earthquake may destroy whole towns in the course of several minutes and even seconds.

The typical large earthquake starts with fracturing within the earth where rocks are subjected to increasing strain until they break. The sudden fracturing is violent enough to vibrate the surrounding solid rocks. These vibrations, called seismic waves, pass through the earth like waves through water: they compress and expand materials in their path or shift it from side to side. Seismic waves travel over the whole surface of the earth and penetrate to its very center.

Although heavy losses may be due directly to fault movement, most of the property damage and loss of life in earthquakes are caused by seismic waves shaking the ground. The waves originate at the fault but spread out from it with such intensity that serious damages result one or two hundred miles away.

While the degree of shaking tends off with distance from the center of disturbance, it varies greatly depending on the solidity of the ground on which structures stand, other circumstances being equal, the intensity of shaking, and, consequently, the destructive effects are much greater on unconsolidated foundation than they are on firm rocks.

II

It has been scientifically proved that the majority of earthquakes are directly connected with mountain-making processes and generally occur in young mountains which have not yet ceased growing.

However, in some cases earthquakes may occur in older mountains, in which the mountain-making processes have been revived. Almost all the destructive earthquakes which have occurred within living memory belong to this class of the so-called tectonic earthquakes.

However, there are other seismic phenomena which are not directly connected with mountain-making processes. These are known as volcanic earthquakes. Volcanic earthquakes are due to the explosion of volcanic gases, when the free escape of magma from the vent of the volcanic crater to the earth’s surface is in some way obstructed. Such shocks usually take place during periods of violent volcanic eruptions and may be the cause of terrible catastrophes and destructions. But they do not spread over areas as large as those involved in tectonic earthquakes.

Besides the above mentioned earthquakes there are others known as collapse earthquakes. These ossur mostly in the regions where readily soluble rocks are widely distributed. Some regions contain underground caves which are sometimes very large. It is clear that if the roofs of such caves are not sufficiently strong, they may give way under the weight of overlying strata and fall down into the cave. This latter type of earthquake has a very limited range of action.

 

Ex.1.

Найдите в тексте и выпишите английские эквиваленты следующим словам и выражениям:

· в течение нескольких минут

· растрескивание; внезапное растрескивание

· подвергаться возрастающему напряжению

· проходить через землю подобно морским волнам

· сжимать и расширять материалы

· передвигать из стороны в сторону

· проникать в центр земли

· тяжелые потери

· затухать с расстоянием от центра нарушения

· изменяться в зависимости от прочности почвы

· при прочих равных условиях

· следовательно

· разрушительное влияние

· тем не менее, однако

· быть непосредственно связанными с …

· свободное извержение магмы из жерла вулкана

· кроме вышеупомянутых …

· легко растворимые породы

· понятно, что …

· иметь ограниченный диапазон действия

· было научно доказано, что…

 

Ex.2.

Выберите правильный вариант из предложенных ниже.

1) The whole towns may be destroyed ______ several minutes.

a. because of

b. of course

c. in the course of

2) Rocks are subjected to increasing strain ______ they break.

a. unless

b. until

c. till

3) Seismic waves pass ______ the earth like waves pass ______ water.

a. though

b. through

c. although

4) ______ heavy losses may be due to fault movements most are caused by seismic waves.

a. though

b. although

c. through

 

Ex.3.