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

INtrusive· magma cools deep INside crust· INtrudes, or ENters, other rocks to cool and harden· ex. granite

EXtrusive· volcanic eruptions EXpose magma to Earth's surface where it cools and hardens

magma EXposed 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 sedimentchange 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

Rock Notes

Metamorphic Rock· "to change form"· high temp. and pressure deep inside Earth can cause minerals in rocks to become unstable and rearrange into layers (foliation) or form larger crystals· NO MELTING OCCURS!!!!

melting rock produces magma (igneous rock)· helps geologists study temp. and pressure conditions, plate tectonic movements, composition of original rock and the geologic history when rock metamorphosed

NONFOLIATED· formed by high temperature, but low pressure equal on all sides· no layers· ex. marble

Foliated vs. Nonfoliated

· alternating dark and light layers due to extreme pressure· ex. slate

FOLIATED

Rock Cycle· any of the 3 rock types can be changed into another rock type· possible changes and outcomes

weathering, deposition, and lithification = sedimentarychanges in pressure or temp. = metamorphicmelting and cooling = igneous