Rocks And the Rock Cycle

Chemical vs. Physical Stability of Rocks Tendency to keep its chemical structure Lower temperatures make more stable rock Higher temp. less stable Have natural weaknesses in structure Break along JOINTS

3 Rock Types: Sedimentary Igneous Metamorphic

The Rock Cycle

Igneous Rocks Formed by volcanic activity Lava melted rock on Earth’s surface Molten rock under Earth’s surface magma

Fractional Crystallization Partial Melting Dif. Minerals melt @ dif. temperatures Fractional Crystallization Dif. Minerals form crystals @ dif. Times Larger crystals usually 1st

Igneous Rocks Large crystals - cooled slowly underground Small crystals - cooled quickly at surface Quick cooling can produce bubbles or a glass too

Igneous Rocks Felsic IR (most light color) Mafic IR (dark color) High silica Granite, pumice Mafic IR (dark color) Low silica High in iron & magnesium Basalt, gabbro

Intrusive Igneous Rock Extrusive Igneous Rock Formed underground Cools slowly Large crystals Granite Formed above ground Cools quickly Small crystals Pumice

Sedimentary Rocks: Form only @ surface Fossils

Sedimentary Rocks

Types Of S.R. Chemical Organic Clastic Evaporates Halite, gypsum coral, clams, plankton Limestone Clastic Broken pieces of older rock Sandstone, conglomerate

Limestone Fossilized Coral Reef

Metamorphic Rocks High temperatures & pressure deep inside near magma

Metamorphic Rocks Foliated - striped Non-foliated