Published on January 14, 2008
Rocks: Rocks Igneous Sedimentary Metamorphic Rock Cycle Igneous RocksFire Rocks: Igneous Rocks Fire Rocks Hot melted rock material cooled and hardened Formed by Lava magma Igneous Rocks from magma: Igneous Rocks from magma Magma Less dense Slowly rises to the surface Cools and hardens before it reaches the surface Cools slowly Mineral & crystals have a long time to form Mineral grains are large Igneous Rocks from magma: Igneous Rocks from magma Granite Most common rock from magma Pink or gray colored Mineral is feldspar White mineral is quartz Black mineral is mica Contains more light colored minerals Igneous Rocks from Lava: Igneous Rocks from Lava Lava- magma that reaches Earth’s surface through a volcano Cools and hardens at Earth’s surface Cools faster than magma Smaller mineral grains Sometimes no mineral grains Rocks formed from lava Rhyolite Basalt Obsidian Igneous Rocks from Lava: Igneous Rocks from Lava Rhyolite Basalt Obsidian- actually glass and not a mixture of minerals Sedimentary RocksRocks from Pieces: Sedimentary Rocks Rocks from Pieces Formed at Earth’s surface when sediments harden into rock. Includes: bits of existing rocks, minerals, and organic materials Most sedimentary rocks are layered. Three types of sedimentary rocks Clastic Chemical Organic (once living) Sedimentary RocksClastic Rocks: Sedimentary Rocks Clastic Rocks Pieces of rock, minerals, and organic materials cemented together Bits can be as small as single grains of mud or as large as boulders. Examples: Conglomerate Shale sandstone Sedimentary RocksChemical Rocks: Sedimentary Rocks Chemical Rocks Form when rich in dissolved minerals evaporates, leaving the minerals behind, or when chemical changes form minerals Examples: Rock gypsum Rock salt Some limestone Sedimentary RocksOrganic rocks: Sedimentary Rocks Organic rocks Formed from remains of plants and animals or from parts, such as shells, or organisms Sometimes contain fossils Examples: Coal limestone Metamorphic RocksA change of identity: Metamorphic Rocks A change of identity New rocks that form from existing rock due to changes in heat, pressure, or chemicals (metamorphism). These changes result in a change in texture (size and shape of mineral grains) Three metamorphism conditions. Contact metamorphism Regional metamorphism Burial metamorphism Metamorphic RocksA change of identity: Metamorphic Rocks A change of identity Contact Metamorphism Temperature and not pressure causes a change Regional Metamorphism Buried deep below Earth’s surface High temperature and pressure Burial Metamorphism Least amount of change Low temperature and pressure Metamorphic RocksA change of identity: Metamorphic Rocks A change of identity Banded metamorphic rocks Look as if they contain bands, or thin layers May look wavy or strainght Gniess- similar to granite Slate- forms from shale Non-banded metamorphic rocks Mineral grains not lined up Texture is massive Marble-forms from limestone Quartzite-from sandstone Rock Cycle: Rock Cycle All rocks can be changed into another rock through metamorphism The rock cycle may “move”, or change, in many ways.