1. 3.2 – Igneous Rocks

2. The Formation of Magma
magma: liquid rock that forms deep underground The three factors that affect whether a rock will melt include: ~ temperature ~ pressure ~ presence of fluids in the rock

3. lava: liquid rock at the surface
magma
igneous rock: rock that forms when magma (underground) or lava (on the surface) hardens into a solid

4. igneous rocks are classified on their texture and composition texture of igneous rock is determined by the size of the crystals in the rock size of the crystals is determined by the cooling rate of the magma/lava cooling rate of the magma/lava is determined by where the material is found

5. Textures of Igneous Rocks
intrusive igneous rock: igneous rock formed inside the Earth from magma magma will cool very, very slowly which allows large mineral crystals to form coarse-grained texture: igneous rocks composed of large, well-developed mineral crystals

7. extrusive igneous rock: igneous rock formed on Earth’s surface (exterior) from lava lava will cool rapidly which will only allow small mineral crystals to form fine-grained texture: igneous rocks that are composed of small crystals

9. sometimes lava will cool immediately so no crystals will form because there isn’t any time for that process
still considered an extrusive igneous rock because it forms on the surface (exterior)
glassy texture: igneous rock with no crystals

10. Chapter 6

11. large bodies of magma take thousands and thousands of years to cool
some minerals crystalize out sooner than others due to their composition
this causes some rocks to have a mixed texture
porphyritic texture: igneous rock that has large crystals embedded within a mass of smaller crystals

13. Composition of Igneous Rock
mineral composition of an igneous rock is determined by the chemical composition of the magma granitic: lighter colored rocks which are made mostly of quartz and feldspar these make up most of the continental crust of Earth

14. includes rocks such as granite, rhyolite, obsidian, and pumice

15. basaltic: darker colored rocks which are made mostly of iron-rich minerals like hornblende, olivine and feldspar make up most of the oceanic crust includes the rocks basalt and gabbro.