Igneous Rocks

______ does NOT affect the type of igneous rock that forms.

• the composition of magma

• the rate at which magma cools

• the size of the erupting volcano

_______ rocks form when lava cools on Earth's surface

• intrusive

• extrusive

• coarse-grained

Which igneous rock has no visible crystals?

• gabbro

• granite

• obsidian

Why does pumice, an igneous rock, have holes?

• it forms from gas-rich lava

• it forms deep beneath Earth's surface

• it forms from magma that is rich in silica

Intrusive igneous rocks are made of

• small particles of ash

• mostly volcanic glass

• large, interlocking crystals

Which term does NOT describe the texture of an extrusive igneous rock?

• layered

• fine-grained

• coarse-grained

In addition to texture, which factor is also used to classify igneous rocks?

• overall color

• pressure and temperature

• the type of cement between the grains

Intrusive rocks contain ________ interlocking crystals

• large

• small

• invisible

Which of the following is an example of an intrusive igneous rock?

• pumice

• basalt

• granite

Extrusive rocks generally have __________ amounts of silica.

• higher

• lower

• zero