High-Q | English פסיכומטרי

Reading Comprehension

TEXT 5

To expand our knowledge of the earth, the USSR started a deep borehole drilling program to investigate geological theories about the planet's crust. The Kola Peninsula in the USSR was selected, and drilling began in 1970. By the mid-1980s the borehole was more than eleven kilometers deep, the deepest penetration of the surface of the earth yet attempted. From this depth it takes 18 hours to hoist samples to the surface. 5 The thickness of the earth's crust ranges from 80 kilometers in mountainous areas to just 10 kilometers beneath the ocean floor; the average around the world is 32 kilometers. The borehole, therefore, has already eaten its way through one-third of the earth's surface. Russian engineers have achieved the feat with modern drilling technology. The main body of the drill, a string of metal pipes weighing more than 300 10 tons, can withstand the high pressures and temperatures of the earth's interior. The Kola borehole has disproved some theories and has established many new facts. Previously, the earth's three-tier structure was thought to consist of a thin sedimentary layer, a granite layer as deep as seven kilometers, and finally a basalt layer that descends to the core of the earth. 15 But the drill has revealed that the sedimentary layer reaches a depth of nearly three kilometers, and at eleven kilometers the drill still has not struck the basalt layer. Scientists have also discovered that the rock between five and seven kilometers deep is actually less dense than that above it, and that the temperature is nearly double the previous estimates. At seven kilometers it is 180 degrees Celsius, not 100 degrees as 20 once believed; the temperature increases 2.5 degrees every 100 meters. The heat makes the minerals in the rock give off water; this creates tremendous pressure, causing the rocks to shatter and crack.

21. It can be inferred that one of the problems with trying to understand the earth's crust by drilling into it is - (1) the harsh conditions deep below the surface (2) the lack of proper instruments for evaluating conditions deep within the earth (3) lack of funding for the very high expenses associated with deep drilling projects (4) the great thickness of the earth's crust in most areas

22. The purpose of the third paragraph is - (1) to describe a theory which has been called into question by the Kola Borehole (2) to describe some new findings resulting from the Kola Borehole project (3) to describe how the findings of the Kola Borehole raise problems for an existing theory about the earth’s crust (4) explain how the Kola Borehole was made

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