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Rocks Igneous Metamorphic Sedimentary Objectives: • Explain how rocks form. • Distinguish between the three main types of rocks. • Identify rock samples based on physical characteristics. Igneous Rocks Terms: Types of Igneous Rocks Intrusive igneous rocks form from magma beneath the Earth’s surface. Extrusive igneous rocks form from lava on the Earth’s surface. magma - beneath the surface Igneous Rock lava magma pool magma Igneous – From Fire Extrusive Intrusive lava volcano or fissure glassy holes from gas basaltic – dark color high % -iron -magnesium magma beneath surface large crystals no holes granitic - light color high % -calcium -silica • Intrusive igneous rocks have large crystals that are easy to see. • Extrusive igneous rocks do not have large crystals that you can see easily. intrusive igneous rock extrusive igneous rock Granite • • • • • intrusive igneous rock light gray, pink or white feels a little rough more than one mineral can be seen hard to scratch with a nail Pumice • • • • • extrusive igneous rock light tan or white full of tiny bubbles light weight often floats on water Obsidian • • • • extrusive igneous rock looks like black glass red or white spots or streaks feels very smooth Gabbro • • • • • intrusive igneous rock dark gray to black feels a little rough more than one mineral can be seen hard to scratch with a nail Rhyolite • • • • extrusive very fine grained pinkish-grey color sometimes has dark streaks Basalt • • • • • extrusive rock dark grey or black feels little rough different minerals can be seen hard to scratch with a nail Which are intrusive and which are extrusive rocks? Granite Pumice intrusive Extrusive Obsidian Basalt Extrusive Extrusive Rhyolite Gabbro Extrusive intrusive Can you identify this igneous rock? Physical properties: light colored floats in water has air bubbles Pumice Intrusive or extrusive extrusive Can you identify this igneous rock? Physical properties: dark colored not glassy more than one mineral is visible Gabbro Intrusive or extrusive extrusive Can you identify this igneous rock? Physical properties: light gray, pink or white feels a little rough more than one mineral can be seen graite Intrusive or extrusive intrusive Can you identify this igneous rock? Physical properties: dark grey or black feels a little rough air holes basalt Intrusive or extrusive extrusive Can you identify this igneous rock? Physical properties: looks like black glass red or white spots or streaks feels very smooth obsidian Intrusive or extrusive extrusive Can you identify this igneous rock? Physical properties: fine grained pinkish-grey color sometimes has dark streaks rhyolite Intrusive or extrusive extrusive Sedimentary Rocks Sedimentary Rocks • sedimentum means “to settle” • rocks form from sediments that have been pressed together • sediments come from: • plant or animal remains • minerals dissolved in water • large rocks that have broken up Sediment is normally deposited in horizontal layers parallel to the Earth’s surface Three Types of Sedimentary Rocks Detrital Chemical Organic sediment deposited by: wind ice water gravity minerals left behind: geysers hot springs salt water fossils plants / animals coal limestone Detrital Sedimentary Rocks - Identified by Grain Size • • • • clay sized – shale silt sized – siltstone sand sized – sandstone pebble sized- conglomerate Siltstone Conglomerate Shale Sandstone conglomerate shale siltstone sandstone Conglomerate • may be tan, red, or white • full of pebbles of sand • hard to scratch – breaks first sandstone • • • • layers of slightly different colors may be red, brown, or gray granular appearance can scratch off grains of sand Siltstone shale • • • • • may be red, brown, or gray feels smooth splits into almost flat layers smells like mud when wet easy to scratch Chemical Sedimentary Rock Mineral Rich Water Evaporates • salt water • geysers • hot springs Examples: • halite – rock salt • gypsum - chalk limestone • • • • may be black, gray or white may feel rough or smooth easy to scratch powder from scratch bubbles with vinegar Organic Sedimentary Rock Fossilerous Limestone and Coal fossil – remains or trace of a once living plant or animal coal – fossilized plant limestone – fossilized ocean organisms chalk = limestone Fill in the name of a rock (s) that fits each of the properties. easy to scratch shale limestone hard to scratch sandstone conglomerate bubbles with acid limestone does not bubble shale pebbles conglomerate no pebbles sandstone Metamorphic Rock Metamorphic Rock heat marble limestone pressure Metamorphic – change of form Great pressures and heat • look different • recrystallized • chemically changed Any existing type of rock can morph • igneous • sedimentary • metamorphic igneous granite gniess detrital sedimentary sandstone quartzite limestone marble chemical sedimentary Metamorphic marble schist gniess Slate Marble • • • • • white, yellow or tan color mineral grains can be seen powder from scratch bubbles with acid easy to scratch with a nail nonfoliated gniess • colors are usually black and white, black and red or black and brown • minerals in ribbon like layers • hard to scratch with a nail • foliated Schist • • • • black to silvery minerals in leaf- like layers soft and easy to scratch with a nail foliated slate • • • • black, grey, red or green easy to scratch with a nail splits into thin, flat, smooth plates foliated Classifying Metamorphic Rocks • Texture differences • Two main groups – Foliated • visible layers or leaves • bands of different colored minerals - Nonfoliated • no distinctive bands or layers • no pattern to any visible mineral grains Foliated and Nonfoliated Rocks Marble (nonfoliated) Slate (foliated) Identify the properties of the following metamorphic rocks Gneiss – Schist – Slate - Marble hard to scratch gneiss minerals seen gneiss, schist, marble bubbles with vinegar marble foliated, gneiss, slate, schist easy to scratch schist, slate, marble minerals not seen slate does not bubble gneiss, schist, slate nonfoliated marble Rocks Three classes metamorphic sedimentary igneous two kinds three kinds two kinds foliated nonfoliated detrital chemical organic intrusive extrusive The Rock Cycle “a model in diagram form” compaction cementation weathering erosion melting heat and pressure cooling The word “igneous” means... A. from fire B. from water C. to be ignited What is magma? A. molten rock on the earth’s surface B. molten rock below the earth’s surface C. volcanic ash What is lava? A. an abrasive in soap B. molten rock above the earth’s surface C. molten rock below the earth’s surface Igneous rock forms from …. A. lava B. magma C. either lava or magma Obsidian, granite, pumice, and basalt are examples of ….. A. igneous rocks. B. sedimentary rocks. C. metamorphic rocks. The nickname for this rock is “volcanic glass” A. pumice B. shale C. obsidian This rock is has colored dots. A. pumice B. granite C. marble This rock can float in water. A. pumice B. limestone C. sandstone The Hawaiian Islands are made of this rock. A. obsidian B. basalt C. sandstone Sedimentum means…. A. to settle B. solid rock C. move slowly Sedimentary rocks form from... A. sediments pressed together. B. rocks cemented together. C. both A and B Conglomerate, sandstone, and limestone are examples of …. A. sedimentary rocks. B. igneous rocks. C. metamorphic rocks. A rock made from pebble sized rocks cemented together with mud. A. sandstone B. limestone C. conglomerate This rock is made from mud and forms in layers. A. shale B. slate C. gneiss This rock is made from granite. A. marble B. schist C. sandstone These rocks are formed from existing rocks. A. igneous rocks B. sedimentary rocks C. metamorphic rocks Metamorphic rocks form when rocks are placed under …. A. mud in a river bed. B. frozen ice. C. heat and pressure. Metamorphic rocks form from... A. igneous rocks. B. sedimentary rocks. C. both A and B This rock is formed from quartz, feldspar and mica. A. schist B. marble C. gneiss This rock makes “chalk” marks A. sandstone B. limestone C. slate Name this rock….. A. gniess B. granite C. marble Name this rock….. A. obsidian B. basalt C. marble Name this rock…… A. sandstone B. pumice C. conglomerate Name this rock … A. shale B. basalt C. schist Name this rock … A. sandstone B. pumice C. limestone Name this rock….. A. obsidian B. granite C. marble Name this rock….. A. obsidian B. granite C. slate Name this rock … A. shale B. schist C. sandstone Name this rock … A. sandstone B. slate C. obsidian Name this rock….. A. schist B. granite C. gniess End of Presentation Resources and Citations Resources: Text : www.tx.science.glencoe.com Clip art: http:dgl.microsoft.com Sound: www.soundamerica.com Rock Pictures: www.rockhound.com Rocks and Minerals: The Hard Facts. Rainbow Educational Media. 1987.
