3 Igneous Rocks Formed when molten rock cools and solidifies. As rock cools, minerals in rock cool The slower rock cools more crystalsExtrusive vs. IntrusiveExtrusive - Cools on E’s surface; air pockets; glassy; few or small crystalsExamples: Obsidian & Basalt (sea floor)Intrusive – magma cools while trapped beneath E’s surface. Cooling takes millions of yrs.; Bigger crystalsExample: Granite
5 Sedimentary RocksFormed when pieces of rock or sediment (fragments of older rock & fossils, or living things, & minerals), get squeezed and cemented together.Form near surface (weathering & erosion make sediments); May have fossilsSediments b/cm rocks when buried(1) Layers of sediment get compressed from weight above, forming rock (LITHIFICATION)(2) Minerals dissolved in water seep b/w bits of sediment and CEMENT them togetherNamed according to size of fragments they containsConglomerate – pebbles & big fragmentsSandstone – sandMudstone – fine mud (CAN’T SEE INDIVIDUAL GRAINS)Limestone – fossils of organisms that live in the water.
6 Types of Sedimentary Rocks A. Clastic: form fr. broken fragments of other rocks (usu. Held together by cement)Ex.: Conglomorate, sandstone, mudstoneB. Chemical: form fr. minerals that precipitate out of solution.Ex.: Tufas (calcium cabonate rocks)C. Organic: form as a result of organic (living) processesEx. :Limestone made from shells of organisms or rocks w/ fossils in them or Anthracite (coal) made from plant matter that did not get decomposed.
7 Tufas (salt towers): Chemical Limestone Cliffs of Dover: Organic Conglomerate: ClasticTufas (salt towers): ChemicalLimestone Cliffs of Dover: OrganicSandstone: Clastic
8 Metamorphic RockFormed when HEAT, PRESSURE, or CHEMICAL PROCEESES w/in E cause changes in the texture and mineral content of rocks.Rock undergoes a change w/out melting over millions of yrs.Fossils get destroyedUsually form at bases of Mts.; near magma, hot springs, faults, or plate boundaries.Examples:Limestone + heat + pressure MarbleMudstone/Shale + heat + pressure Slate
9 Metamorphic rocks may have foliations: Minerals in rocks realign into bands or stripes in metamorphic rocks.
10 Rock CycleProcess of events in which rocks can be weathered, melted, altered, and formed over millions of yrs.
11 Rock Cycle Processes SEDIMENTARY ROCKS: on surface Weathering / Deposition of Sediments / Cementation (lithification) Sedimentary RockIGNEOUS ROCKS: On surface (extrusive) or interior (intrusive) Melting / Cooling & Solidifying Igneous RockMetamorphic Rock: Usually inside Earth depths associated w. higher pressures & temps.)Heat / Pressure Metamorphic RockWeathering: wind & water breaks rocks down into fragments (Makes sedimentary)Cementation: Water “glues” sediment together to make rock
12 Rocks viewed with a microscope Microscope View of GRANITE (IGNEOUS):Minerals are randomly orientedMicroscope View of GNEISS (METAMORPHIC):Minerals are NOT randomly arranged. (Green/Blue minerals are lined up in parallel layers or foliations)
13 Rocks viewed with a microscope Sandstones (Sedimentary): Grains of sand cemented together with pore space between.
14 Answer these questions on lined paper in complete sentences. Rock ID Check UpAnswer these questions on lined paper in complete sentences.Which rocks were igneous? List # and name.Which of igneous rocks would be considered EXTRUSIVE?Which rock was an intrusive igneous? What characteristic can you observe to confirm that it is intrusive?Did granite form quickly or slowly? How do you know?Which rocks were sedimentary? List # and name.Which sedimentary rocks were clastic?Which sedimentary rock was organic or chemical?Which rocks were metamorphic? List # & name.Shale can turn into slate. What conditions would change shale into slate?Which rock (or rocks) could you find fossils in? Support your answer.