Chapter 4: Magma and Igneous Rocks

The difference between lava and magma is that.

• magma is light in color, and lava is dark

• magma usually has a mafic composition, and lava usually has a felsic composition

• magma is found beneath the Earth’s surface, whereas lava has reached the surface

• magma flows more quickly than lava

A blob-like igneous rock body that has cooled beneath the surface of Earth is called a.

• guyot

• pluton

• lava flow

• andesite

A dike is.

• a sheetlike intrusion that lies parallel to surrounding layers of sedimentary rock

• a cooled layer of lava

• an intrusion formed within the magma chamber of a volcano

• a sheetlike intrusion that cuts across preexisting layers

A sill is.

• a sheetlike intrusion that lies parallel to surrounding layers of sedimentary rock

• a cooled layer of lava

• an intrusion formed within the magma chamber of a volcano

• a sheetlike intrusion that cuts across preexisting layers

Igneous rocks.

• are formed through the freezing of melt

• can be produced at the surface of the Earth as well as deep below the surface

• are the most common type of rocks within Earth

• all of the above

Very early in Earth’s history, it was so hot that the surface was likely entirely molten.

• True

• False

When magma crystallizes, are formed.

• intrusive igneous rocks

• extrusive igneous rocks

• volatiles

• pyroclastic debris

Volatiles refer to substances that.

• crystallize most rapidly out of a melt

• melt immediately upon contact with a hot body of magma

• have a tendency to evaporate and are stable as gases

If the volatile content of magma is increased, its viscosity will.

• increase

• decrease

• stay the same

If a body of magma becomes more felsic, its viscosity will.

• increase

• decrease

• stay the same