(3) Rock Cycle

• Rock Cycle

  • describes transitions through geologic time among the three main rock types: sedimentary, metamorphic, and igneous.
• Igneous Rocks

  • formed by magma and lava as it cools
• Intrusive Igneous Rocks

  • formed when magma cools and solidifies before it reaches the surface
  • generally wholly crystalline and characterized by large crystal sizes visible to the naked eye because they cool slowly
  • well-formed
• Extrusive Igneous Rocks

  • formed when magma exits (volcanic vent) and cools above (or very near) the Earth's surface
  • rocks that form at erupting volcanoes and oozing fissures
• Types of Intrusive Igneous Rocks

  • diorite
  • gabbro
  • granite
  • pegmatite
• Types of Extrusive Igneous Rocks

  • andesite
  • basalt
  • obsidian
  • pumice
  • rhyolite
  • scoria
• Sedimentary Rocks

  • made when sediments (sand, gravel, and dirt) are pressed together over time and become a rock
  • formed in layers
• Formation of Sedimentary Rocks

  • Weathering of preexisting rocks (Weathering and Erosion)
  • Transport of weathering products
  • Deposition of the material (Deposition)
  • Sand, dirt, clay, and/or small rocks are pressed together over time so that the space between the pieces gets smaller (Compaction)
  • Sediments are hardened by the precipitation of mineral matter in the pore spaces (Cementation)
• Metamorphic Rocks

  • made from other rocks
  • heat and pressure help change an igneous or sedimentary rock to this kind of rock
• Crystals

  • are different atoms that are formed in a pattern
  • can be big or small, fat or thin
• Grains

  • smaller pieces of rock or sediment
  • grain size is something that is used a lot to help decide the rock type
• Magma

  • molten rock
• Lava

  • when magma already exits the volcano and starts to cool on the earth's surface
• Granite

  • igneous rocks which were formed by slowly cooling pockets of magma that were trapped beneath the earth's surface
  • used for long-lasting monuments and for trim and decoration on buildings
• Pumice

  • igneous rocks that are formed when lava is cooled quickly above ground
  • it is so light, many of this type of rock will actually float in water
  • a kind of glass and not a mixture of minerals
  • often used as a decorative landscape stone
• Obsidian

  • glass-like structure
  • edges of this rock are very sharp
• Sandstone

  • sedimentary rocks made from small grains of the minerals quartz and feldspar
  • often used as building stones
• Shale

  • sedimentary rock formed from clay that is compacted together by pressure
  • used to make bricks and other material that is fired in a kiln
• Limestone

  • sedimentary rocks that are made from the mineral calcite which came from the beds of evaporated seas and lakes and from sea animal shells
  • used in concrete and is an excellent building stone for humid regions
• Schist

  • metamorphic rocks that can be formed from basalt, shale, or slate through heat and pressure
• Gneiss

  • metamorphic rocks that may have been granite, but changed because of heat and pressure
• Clastic Sedimentary Rocks

  • composed predominantly of broken pieces or clasts of older weathered and eroded rocks
  • classified based on grain size, clast, and cementing material composition (matrix), and texture
• Organic Sedimentary Rocks

  • form from the accumulation and lithification of organic debris, such as leaves, roots, and other plant or animal material
• Chemical Sedimentary Rocks

  • formed by chemical precipitation that begins when water traveling through rocks dissolves some of the minerals
• Foliated Metamorphic Rocks

  • when rocks with flat or elongated minerals are put under immense pressure and the minerals line up in layers
• Non-foliated Metamorphic Rocks

  • are formed the same way as foliated metamorphic rocks, but do not contain the minerals that tend to line up under pressure and thus, do not have a layered appearance of foliated rocks
• Coal

  • a sedimentary rock formed over millions of years from compressed plants
  • "best" example of sedimentary rock
• Ranks of Coal (lowest to highest)

  • Peat
  • Lignite
  • Bituminous
  • Sub-bituminous
  • Anthracite
• Origin

  • a way you can classify rocks as igneous, sedimentary, or metamorphic
• Volcanic Explosion

  • makes directly the formation of pumice rocks