Intrusive igneous rocks

• are formed beneath earth’s surface from magma

• Are coarse grained, made up of large, visible crystals that grow together

• The larger the crystals are, the longer it took for the rock to form- beneath the surface temperature is higher and pressure will keep magma in liquid form

DIORITE

USUALLY FOUND NEAR CRUSTAL PLATE BOUNDARIES AND INSIDE MOUNTAINS

GRANITE

WHAT THE CONTINENTAL CRUST IS MAINLY MADE UP OF

Extrusive igneous rocks

• Form above the earth’s surface from lava

• Are very fine grained (have very small crystals that are visible) or they are glassy

• The smaller the crystals (or none seen at all) means the lava cooled very quickly

SCORIA

VERY FINE GRAINED AND SHARP WITH VISIBLE AIR BUBBLES

BASALT

ROCK THAT MAKES THE SEA FLOOR

PUMICE

VERY VISIBLE AIR BUBBLESLOW DENSITY ALLOWS IT TO FLOAT

OBSIDIAN

VOLCANIC GLASS

• Is this intrusive or extrusive- how do you know?