Intro to Igneous Rocks

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Question 1: Is pumice a sedimentary rock?

• No

• Yes

Answer explanation

No. Pumice is an igneous rock.

Can pumice float on water?

• No

• Yes

Answer explanation

Yes, at least until it gets waterlogged. That's because there are many cavities (called vesicles) that are filled with air.

Is scoria an intrusive type of igneous rock?

• No

• Yes

Answer explanation

No. Scoria is an extrusive type of igneous rock.

Does scoria typically form deep inside the Earth?

• No

• Yes

Answer explanation

No. Scoria forms on the top of lava flows and sometimes in ejected lava (extra info for those interested: whether lava ejected from a volcano forms pumice or scoria also depends on the magma's chemical composition).

Is basalt a metamorphic rock?

• No

• Yes

Answer explanation

No. Basalt is an igneous rock (of the extrusive type).

Is basalt in the oceanic crust?

• No

• Yes

Answer explanation

Yes. Basalt is a major part of the oceanic crust. It may be covered by other rock types (e.g., sedimentary).

Tags

NGSS.MS-ESS2-3

Does granite often contain large crystals that are big enough to see without a microscope?

• No

• Yes

Answer explanation

Yes. Granite cools so slowly, that crystals have time to grow large enough for us to see them.

Is granite formed from cooled lava?

• No

• Yes

Answer explanation

No. Granite is formed from cooled magma which then becomes solid. Magma that exits the Earth's surface in a liquid state is called lava.