2. The Rock Cycle

4. Magma Magma - complex mixture of high temperature solid, liquid, and gaseous material. Dissolved gasses - mostly H 2 O, SO 2, CO 2 When the temperature is high enough (and the pressure* is low enough), some solid Earth materials will begin to melt, forming magma. *If the pressure is too high, melting will not occur – which is why magma is more commonly formed in the crust than the mantle, even though mantle temperatures are much higher than crust temperatures.

5. Properties of Magma Viscosity – resistance of a fluid to flow (low viscosity=water; high viscosity=syrup) http://www.earth.northwestern.edu/people/seth/107/Rocks/magviscosity.htm

6. Bowen’s Reaction Series felsic Felsic igneous rocks contain minerals with low melting points Mafic igneous rocks contain minerals with high melting points Intermediate igneous rocks contain minerals with intermediate melting points

7. felsic

8. Texture Texture - refers to the size of mineral crystals. The more slowly a magma cools, the more time crystals have to grow. coarse- grained (phaneritic). Magma that cooled slowly produces large crystals, and the resulting rock is coarse- grained (phaneritic). fine-grained (aphanitic) In magmas that cooled quickly only small crystals form, and the resulting rock is fine-grained (aphanitic). Crystalline Igneous Rock Texture

9. Texture Texture - refers to the size of mineral crystals. The more slowly a magma cools, the more time crystals have to grow. Porphyritic Texture Sometimes a magma will have a complex cooling history, and may stay at a mineral’s crystallization temperature for a long time, allowing those mineral crystals to grow large. If the magma is later cooled more quickly, only smaller crystals of the other minerals will form. Crystalline Igneous Rock Texture

10. Felsic

11. Some Some magmas cooled too fast for minerals to form. The rocks are made of glass and contain no minerals, so are NOT described using the felsic-intermediate-mafic system. obsidianscoria bombs!