Intrusive Igneous Features

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

• Intrusive rocks cool quickly at the surface, while extrusive rocks cool slowly at depth.

• Intrusive rocks cool slowly at depth, while extrusive rocks cool quickly at the surface.

• Intrusive rocks are formed from lava, while extrusive rocks are formed from magma.

• Intrusive rocks are always felsic, while extrusive rocks are always mafic.

How can the size of mineral grains be used to distinguish between plutonic and volcanic rocks?

• Plutonic rocks have tiny grains, while volcanic rocks have large crystals.

• Plutonic rocks have large crystals, while volcanic rocks have tiny grains.

• Plutonic rocks have no crystals, while volcanic rocks have visible crystals.

• Both plutonic and volcanic rocks have large crystals, but their colors differ.

Which of the following volcanic rocks has a silica (Si) content between 52% and 62%?

• Rhyolite

• Andesite

• Dacite

• Basalt

What type of lava is exclusively erupted from mid-ocean ridges?

• Andesitic

• Rhyolitic

• Dacitic

• Basaltic