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Earth, Then and Now

Scientists believe that the earth formed from a cloud of dust
particles about 4.6 billion years ago. The dust cloud came together
to form a ball of molten, or melted rock. The ball cooled over
several million years, forming a crust on the outside.
The surface of the earth is the crust. It is a thin layer of
rock. It ranges from three miles thick under the deepest parts of the
oceans to twenty-two miles thick under mountains peaks. Crust is
always moving. The continents drift apart, the oceans rise and fall.
Beneath the crust is the mantle, a layer of very hot,
sometimes molten rock about 1,800 miles thick.
At the center of the earth is the core. The core is made up
of two parts: the outer core, which is made up of molten rock, and
the solid inner core. The core has a radius of about 2,100 miles.

Comprehension Questions

I. Say which of the following statements are false and
which are true. Correct the false statements to make them
true.

1. Scientists think that the Earth formed about 4.6 billion years
ago.

2. The surface of the Earth is the crust.

3. The crust is not a thin layer of rock.

4. The mantle is a layer about 1,800 miles thick beneath the crust.
5. The outer core is made up of molten rock.

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