Rock Notes Rock Types & The ROck Cycle Ch. 6 Igneous Rock · "from fire" · forms when magma (melted rock) cools and hardens · composition limited to the 8 common elements of Earth's crust Intrusive vs. Extrusive IN trusive · magma cools deep IN side crust · IN trudes, or EN ters, other rocks to cool and harden · ex. granite EX trusive · volcanic eruptions EX pose magma to Earth's surface where it cools and hardens magma EX posed to Earth's surface is called lava · ex. pumice Sedimentary Rock · sediment - rocks, mineral crystals, or organic matter that has been broken into fragments · weathering (erosion) transport deposition lithification (turned to rock through compaction and cementation) compaction = to compress or condense (take up less space) cementation = minerals from water glue sediment together · gives us clues about Earth's past · contains valuable resources (ex. water and oil) Clastic vs. nonclastic CLASTIC · formed by weathering processes that broke rock into pebbles, sand, or clay · transported by water, wind, or ice · named based on grain size of sediment · ex. sandstone and shale NONCLASTIC · named based on mineral composition · chemical forms from minerals dissolved in water evaporation causes minerals to precipitate, or fall out, from water · organic forms from the remains of living things · ex. limestone, rock salt, coal Sedimentary Rock Features · give geologists clues about what has happening on Earth when a layer of sediment was deposited · stratification - layering of sediment change in sediment type, change in sea level · ripple marks - caused by wind or water on sand sediment once part of a beach or riverbed · mud cracks - muddy deposits dry and shrink river's flood plain or dry lake bed · fossils - remains or traces of ancient plants and animals