Whatever the cause of the heat may be, we do know that the earth gets hotter       down we dig.

         A．further                     B．the farther              C．the farthest            D．the furthest

Whatever the cause of the heat may be, we do know that the earth gets hotter ________ down we dig．

1. A.
   further
2. B.
   the farther
3. C.
   the farthest
4. D.
   the furthest

Whatever the cause of the heat may be, we do know that the earth gets hotter       down we dig.

         A．further       B．the farther         C．the farthest       D．the furthest

Whatever the cause of the heat may be, we do know that the earth gets hotter       down we dig.

A．further           B．the farther           C．the farthest          D．the furthest

Whatever the cause of the heat may be, we do know that the earth gets hotter       down we dig.

Geologists have been studying volcanoes(火山)for a long time. Though they have learned a great deal, they still have not discovered the causes of volcanic action. They know that the inside of the earth is very hot, but they are not sure exactly what causes the great heat. Some geologists have thought that the heat is caused by the great pressure of the earth's outer layers. Or the heat may be left from the time when the earth was formed. During the last sixty years scientists have learned about radium, uranium, thorium, and other radioactive elements. These give out heat all the time as they change into other elements. Many scientists now believe that much of the heat inside the earth is produced by radioactive elements.

Whatever the cause of the heat might be, we do know that the earth gets hotter the farther down we dig. In deep mines and oil wells the temperature rises about 1 degree F for each 50 feet. At this rate the temperature 40 miles below the earth's surface would be over 4,000 degrees F. This is much hotter than necessary to melt rock. However, the pressure of the rock above keeps most materials from melting at their usual melting points. Geologists believe that the rock deep in the earth may be plastic. In other words, the rock yields(屈服)slowly to pressure but is not liquid. But if some change in the earth's outer layer releases the pressure, the rock melts. Then the hot, liquid rock can move up toward the surface.

4. The subject of this passage is the________.

A. formation of volcanoes

B. results of volcanic action

C. heart of the earth

D. causes of the earth's inside heat

5. The cause for the heat in the interior of the earth is probably________.

A. radioactive elements

B. the great pressure of the earth

C. not determined

D. the heat remaining from the formation of the earth

6. If the temperature at the earth's surface is 20°F, the temperature in a coal mine 500 feet below the surface would, in degree, be________.

A. 40 B. 30 C. 50 D. 120

7. Why doesn't the rock deep in the earth melt as a liquid at such high temperature?

A. Because the temperature isn't high enough to melt it.

B. Because it may be plastic.

C. Because the pressure of the rock above is strong enough to stop it melting.

D. Because there isn't oxygen inside the earth.

Geologists have been studying volcanoes for a long time.Though they have learned a great deal,they still have not discovered the cause of volcanic action.They know that the inside of the earth is very hot,but they are not sure exactly what causes the great heat.Some geologists have thought that the heat is caused by the great pressure of the earth’s outer layers.Or the heat may be left from the time when the earth was formed.During the last sixty years scientists have learned about radium,uranium,thorium,and other radioactive elements.Many scientists now believe that much of the heat inside the earth is produced by radioactive elements.

Whatever the cause of the heat may be,we do know that the earth gets hotter the farther down we dig.In deep mines and oil wells the temperatures rise about 1°F for every 50 feet.At this rate of the temperature 40 miles below the earth’s surface should be over 4 000°.This is much hotter than necessary to melt rock.However,the pressure of the rock above keeps most materials from melting at their usual melting points.Geologists believe that the rock deep in the earth may be plastic,or puttylike（油灰状的）.In other words,the rock yields slowly to pressure but is not liquid.But if some change in the earth’s crust releases the pressure,the rock melts.Then the hot,liquid rock can move up toward the surface.

The cause for the great heat inside of the earth is______.

 A.great pressure of the earth’s outer layers

 B.the heat left from the time when the earth was formed

 C.radioactive elements giving out heat

 D.not sure

According to the passage,______ prevents most rock from melting at its usual melting points.

 A.the pressure of the rock itself

 B.the pressure of the rock above

 C.the pressure of the earth’s outer layers

 D.the heat given out by some radioactive elements

According to the passage,which of the following is NOT true?

 A.The farther down,the hotter the earth gets.

 B.The rock deep in the earth is liquid.

 C.When the pressure releases from the earth’s crust,the rock melts.

 D.Rock would be melted at 4 000°.

Geologists have been studying volcanoes for a long time.Though they have learned a great deal,they still have not discovered the cause of volcanic action.They know that the inside of the earth is very hot,but they are not sure exactly what causes the great heat.Some geologists have thought that the heat is caused by the great pressure of the earth’s outer layers.Or the heat may be left from the time when the earth was formed.During the last sixty years scientists have learned about radium,uranium,thorium,and other radioactive elements.Many scientists now believe that much of the heat inside the earth is produced by radioactive elements.

Whatever the cause of the heat may be,we do know that the earth gets hotter the farther down we dig.In deep mines and oil wells the temperatures rise about 1°F for every 50 feet.At this rate of the temperature 40 miles below the earth’s surface should be over 4 000°.This is much hotter than necessary to melt rock.However,the pressure of the rock above keeps most materials from melting at their usual melting points.Geologists believe that the rock deep in the earth may be plastic,or puttylike（油灰状的）.In other words,the rock yields slowly to pressure but is not liquid.But if some change in the earth’s crust releases the pressure,the rock melts.Then the hot,liquid rock can move up toward the surface.

1.The cause for the great heat inside of the earth is______.

A.great pressure of the earth’s outer layers

B.the heat left from the time when the earth was formed

C.radioactive elements giving out heat

D.not sure

2.According to the passage,______ prevents most rock from melting at its usual melting points.

A.the pressure of the rock itself

B.the pressure of the rock above

C.the pressure of the earth’s outer layers

D.the heat given out by some radioactive elements

3.According to the passage,which of the following is NOT true?

A.The farther down,the hotter the earth gets.

B.The rock deep in the earth is liquid.

C.When the pressure releases from the earth’s crust,the rock melts.

D.Rock would be melted at 4 000°.

Geologists have been studying volcanoes for a long time.Though they have learned a great deal,they still have not discovered the cause of volcanic action.They know that the inside of the earth is very hot,but they are not sure exactly what causes the great heat.Some geologists have thought that the heat is caused by the great pressure of the earth’s outer layers.Or the heat may be left from the time when the earth was formed.During the last sixty years scientists have learned about radium,uranium,thorium,and other radioactive elements.Many scientists now believe that much of the heat inside the earth is produced by radioactive elements.
Whatever the cause of the heat may be,we do know that the earth gets hotter the farther down we dig.In deep mines and oil wells the temperatures rise about 1°F for every 50 feet.At this rate of the temperature 40 miles below the earth’s surface should be over 4 000°.This is much hotter than necessary to melt rock.However,the pressure of the rock above keeps most materials from melting at their usual melting points.Geologists believe that the rock deep in the earth may be plastic,or puttylike（油灰状的）.In other words,the rock yields slowly to pressure but is not liquid.But if some change in the earth’s crust releases the pressure,the rock melts.Then the hot,liquid rock can move up toward the surface.

1. 1.

   The cause for the great heat inside of the earth is______.

   1. A.
      great pressure of the earth’s outer layers
   2. B.
      the heat left from the time when the earth was formed
   3. C.
      radioactive elements giving out heat
   4. D.
      not sure
2. 2.

   According to the passage,______ prevents most rock from melting at its usual melting points.

   1. A.
      the pressure of the rock itself
   2. B.
      the pressure of the rock above
   3. C.
      the pressure of the earth’s outer layers
   4. D.
      the heat given out by some radioactive elements
3. 3.

   According to the passage,which of the following is NOT true?

   1. A.
      The farther down,the hotter the earth gets.
   2. B.
      The rock deep in the earth is liquid.
   3. C.
      When the pressure releases from the earth’s crust,the rock melts.
   4. D.
      Rock would be melted at 4 000°.