4-4 The Earth's Plates

Geologists have determined that the mantle of the earth in some places is hot enough to melt solid rock.  They gather information to make this hypothesis by measuring the temperature of the gases released during volcanoes and earthquakes.  This melted rock; called magma rises to the crust of the earth because it is lighter than the solid rock around it.  Once the magma reaches the surface of the earth it pools in open areas between rocks and cools.

The earth's crust is under pressure.  Geologists believe it has been under pressure for millions of years.  They believe the earth's crust is not smooth, but rather cracked in places.  They call these pieces plates.  Geologists believe there are about ten plates that make up the crust of the earth.  The plates lie very close together most of the time.  When the plates push against each other, slide past each other, or move apart, it is called an earthquake.

Directions: Answer the questions about the earth's plates.

Melted rock from the mantle of the earth is called .

Geologists believe the earth's crust is broken into pieces called .

Geologists believe there are about large pieces.

Which of the following statements is true?

The plates lie very close together all of the time. 
The plates lie far apart from each. 
The plates lie very close together most of the time.

An   occurs when the plates push against each other, slide past each other, or move apart.

Magma rises to the crust of the earth because it is than the solid rock around it.

Geologists believe the earth's crust has been under pressure for of years.