Igneous Rocks

What is the difference between extrusive igneous rocks and intrusive igneous rocks?

Extrusive igneous rocks cool and solidify on the Earth's surface, whereas intrusive igneous rocks cool and solidify beneath the Earth's surface.

Which of the choices lists the four basic compositional groups of igneous rocks, ranging from the highest silica content to the lowest silica content?

Granitic, andesitic, basaltic, ultramafic

What is the difference between "magma" and "lava"?

It is just a name change, and lava is what magma is called if it reaches the surface of Earth

How does magma differ from lava?

Magma exists strictly below Earth's surface, whereas lava is found on Earth's surface.

What factors influence the texture of an igneous rock?

The rate at which the rock cools, the amount of silica that is present in the magma from which it forms, and the amount of dissolved gases present in the magma

What does a porphyritic texture indicate about the cooling history of an igneous rock?

The rock began cooling under the Earth's surface, but then was moved to above the Earth's surface where it finished cooling.

Granite and rhyolite are both ____, but they differ in ____.

felsic; crystal size

Basalt is the ________ equivalent of gabbro.

fine grained

Obsidian exhibits a ________ texture.

glassy

Granite and gabbro ________.

have a similar texture

Which igneous texture is characterized by two distinctively different crystal sizes?

porphyritic

Intrusive igneous rocks are often coarse-grained because ________.

the slow cooling at depth allows large crystals to grow

If magma or lava cools quickly, the resulting igneous rock will have ________.

very small crystals