3 Rocks and the Rock Cycle Free Online FlashCards

What are rocks, and how are they classified?

Rocks are naturally occurring aggregates of minerals. Geologists classify them as igneous, sedimentary, or metamorphic according to how they form.

How do igneous rocks form?

Igneous rocks form when molten rock cools and solidifies.

What is the difference between magma and lava?

Molten rock below Earth's surface is magma; molten rock at the surface is lava.

What texture can form when magma cools slowly underground?

Slow cooling underground allows relatively large mineral crystals to form. Granite is an example.

What forms when lava cools quickly at or near the surface?

Lava cooling quickly at or near the surface forms small crystals. Basalt is an example.

What can form if molten rock cools extremely rapidly?

Extremely rapid cooling can prevent crystals from forming, producing volcanic glass such as obsidian.

How do sedimentary rocks form?

They form from material deposited at Earth's surface or from minerals that precipitate from water.

How do clastic rocks form?

Clastic rocks form when sediment is buried, compacted, and cemented together. Sandstone forms from sand-sized grains.

How do chemical rocks form?

Chemical rocks form when dissolved minerals precipitate from water, often as the water evaporates.

How do biologic rocks form?

Biologic rocks form from accumulated remains of organisms. Many limestones contain shells or other biological material.

What is lithification?

Lithification is the conversion of loose sediment into solid rock.

How do metamorphic rocks form?

Metamorphic rocks form when an existing rock changes under heat, pressure, or chemically active fluids, usually while remaining solid.