'Igneous Rocks' Geology Worksheet printable pdf download

'Igneous Rocks' Geology Worksheet

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IGNEOUS ROCKS

Igneous comes from the Latin word ignis, meaning “fire”. Igneous rock is any rock that

forms from cooled magma or lava.

Extrusive igneous rocks are formed from lava that erupted at the Earth’s

surface. Basalt, pumice and obsidian are common extrusive rocks. Intrusive igneous

rocks are formed when magma cools and hardens below the Earth’s surface. Granite

and gabbro are the most common intrusive rocks.

The texture of igneous rocks depends on the size of their mineral crystals. Rapidly cooling lava

forms fine-grained extrusive rock with small crystals, such as basalt. If lava cools fast enough to

trap air bubbles inside, it can produce a lightweight extrusive rock called pumice. If lava encounters

water, it cools instantly. Since there is no time for crystals to form, a type of volcanic glass called

obsidian is produced. Below the Earth’s surface, slow-cooling magma forms coarse-grained intrusive

rock with large crystals, like granite.

1. Formation of Igneous Rock

Fill in the blanks by looking at the diagram below.

Word Bank

Granite

Basalt

Pumice

Obsidian

Instantly

Very Quickly

Quickly

Slowly

Frothy lava is thrown into the air

Lava flows into a water and cools

and cools ____________, trapping

_____________. There is no time for

pockets of air inside. Rock Name =

crystals to form. Rock Name =

_______________

Magma below the surface cools

Lava outside the volcano cools

____________. The igneous rock

contains large crystals.

contains small crystals.

Rock Name = _______________

'Igneous Rocks' Geology Worksheet