Which statement correctly distinguishes intrusive and extrusive igneous rocks?

Which statement correctly distinguishes intrusive and extrusive igneous rocks?

• A. Intrusive igneous rocks form below the surface and have larger crystals.
• B. Extrusive igneous rocks form below the surface and have larger crystals.
• C. Intrusive rocks form from lava at the surface and have small crystals.
• D. Extrusive rocks form from lava at the surface and have large crystals.

Answer: (A)

The main idea here is that where and how quickly igneous rocks cool determines how big the crystals get. Intrusive igneous rocks crystallize underground from magma, cooling slowly. That slow cooling gives minerals time to grow, so the rocks have visible, larger crystals (coarse-grained textures). Extrusive igneous rocks erupt onto the surface and cool rapidly, which locks crystals into tiny sizes or even forms glassy textures. So the correct statement matches this pattern: intrusive rocks form below the surface and develop larger crystals. For context, granite is a classic example of an intrusive rock with big crystals, while basalt or rhyolite are common extrusive rocks with much smaller crystals due to rapid cooling at the surface. The other ideas mix up where cooling occurs or the resulting texture: extrusive rocks do not typically form below the surface with large crystals, intrusive rocks do not form from lava at the surface with small crystals, and extrusive rocks at the surface do not generally have large crystals because they cool too quickly.

The main idea here is that where and how quickly igneous rocks cool determines how big the crystals get. Intrusive igneous rocks crystallize underground from magma, cooling slowly. That slow cooling gives minerals time to grow, so the rocks have visible, larger crystals (coarse-grained textures). Extrusive igneous rocks erupt onto the surface and cool rapidly, which locks crystals into tiny sizes or even forms glassy textures.

So the correct statement matches this pattern: intrusive rocks form below the surface and develop larger crystals. For context, granite is a classic example of an intrusive rock with big crystals, while basalt or rhyolite are common extrusive rocks with much smaller crystals due to rapid cooling at the surface.

The other ideas mix up where cooling occurs or the resulting texture: extrusive rocks do not typically form below the surface with large crystals, intrusive rocks do not form from lava at the surface with small crystals, and extrusive rocks at the surface do not generally have large crystals because they cool too quickly.