Rock Notes, chap 4

  1. minerals are naturally occurring, inorganic solids with a definite chemical composition and a crystal structure.
  2. rocks are made of minerals.
  3. rocks are mixtures of one or more minerals , rock fragments, volcanic glass, organic matter, or other natural materials.
  4. rock cycle-process where rocks slowly change from one form to another through time.  Any type of rock can change into any other type of rock.
  5. erode-means to wear down
  6. 3 types of rocks are igneous, metamorphic, and sedimentary
  7. principle of conservation of matter-no matter is ever created or destroyed, it is just changed from one form into another. 
  8. any type of rock can be changed into any other type of rock or even into another rock of the same type.
  9. James Hutton, a Scottish scientist, in 1788, came up with the idea of the rock cycle.
  10. sedimentary rock is made up of fragments of other rocks that have been broken down by weathering.
  11. metamorphic rock is made from rocks that have been heated and squeezed by the tremendous pressure inside the Earth.
  12. igneous rock is formed when any type of rock gets melted by the incredible heat inside the Earth.


Igneous Rocks:

  1. igneous rocks are formed when magma or lava cools and hardens.
  2. magma that reaches the Earth’s surface is called lava
  3. intrusive-igneous rocks that form from magma below the surface of the Earth.  They form “IN” the Earth-Intrusive.
  4. intrusive rocks have larger grains because the magma cools very slowly.  The slower the cooling, the larger the grains
  5. grains and crystals are the same thing
  6. extrusive-extrusive rocks are formed from lava cooling on the surface of the Earth.  Extrusive rocks cool quickly causing small grains.  The faster the cooling process, the smaller the grains.
  7. volcanic glass, such as pumice, obsidian, and scoria cooled so fast that they don’t have grains or crystals.
  8. basalitic igneous rocks are dense, dark colored rocks
  9. granitic igneous rocks are less dense, light colored rocks
  10. basalt and granite are igneous rocks

Metamorphic Rocks:

  1. metamorphic rocks are rocks that have been changed by heat and pressure.
  2. metamorphic rocks can be formed from igneous, sedimentary, or other metamorphic rocks.
  3. high temperatures inside the Earth cause the rocks to soften without actually melting.
  4. foliated rocks have their grains (crystals) arranged in layers.  (think “folded” like towels)
  5. slate and gneiss are foliated metamorphic rocks
  6. nonfoliated rocks do not have layers.  Quartzite and marble are nonfoliated metamorphic rocks.

Sedimentary Rocks:

  1. sediments are loose materials such as rock fragments, mineral grains, and bits of shell that have been moved by wind, water, ice, or gravity.
  2.  sedimentary rocks are formed when sediments are pressed and cemented together or when crystals form from solutions.
  3. compaction and cementation-on your rock cycle drawings, this is what forms the sediment into sedimentary rocks.  The tiny particles are pressed together and then cemented by minerals.
  4.  sedimentary rocks often form as layers.  The oldest layers are on the bottom and the newest layers are on the top
  5. fossils are ONLY found in sedimentary rocks
  6. weathering and erosion  cause the formation of sedimentary rocks.  Weathering is the breaking down of rocks into smaller pieces by wind, water, and gravity. 
  7. erosion is the carrying away of these small pieces of rock. 
  8. compaction forms sedimentary rocks when the tiny pieces of sediment are pressed together into new rock
  9. cementation forms sedimentary rocks when water and dissolved chemicals actually cement or glue the tiny pieces of sediment together.
  10. clastic sedimentary rocks are cemented together
  11. sandstone and shale are sedimentary rocks
  12. chemical sedimentary rocks are formed when dissolved chemicals in solutions, such as seawater, form rocks such as halite and gypsum.
  13. organic sedimentary rocks are made of the remains of once-living things, usually shell fish such as clams, corals, and snails.  Limestone is an example of organic sedimentary rock.
  14. coal is an organic sedimentary rock formed from the remains of dead plants that have been chemically changed and cemented together.