Chapter 3 Rocks Why study rocks? - rocks tell the story of your location EX: Indiana is made of mostly limestone = formed in a shallow marine setting = so in the past Indiana was under water How is a rock different than a mineral? Rock = a naturally occurring combination of minerals  Rock will show some of the properties of the minerals that make it up EX: Limestone is made of mainly calcite so it reacts to acid

3 Types of Rocks: 1.Igneous = rock made from cooled magma either above or below ground EX: Granite 2.Sedimentary = rock formed from compacted & cemented sediments EX: Limestone 3.Metamorphic = a rock that has been changed (cooked) by increasing temperature and/or pressure to form a new rock EX: Marble

 Rocks are continually changing from one type to another = Rock Cycle

Igneous Rocks: Formed from cooled magma Can form at 2 locations: 1. Below Ground = Intrusive - slow cooling of magma because ground is insulating = this allows grains/crystals to grow large  Coarse Grained Texture 2. Above Ground = Extrusive - quick cooling = no time for crystals to grow so extrusive igneous rocks have small grains  Fine Grained Texture

Igneous Rock Fine Grained Texture Cont… - Exceptionally quick cooling above ground can give special textures: A. Glassy = lava instantly cooled by seawater = No grains in rock  Very smooth/glassy feel EX: Obsidian B. Pyroclastic Texture = magma cooled instantly by being shot into the air (i.e. volcano)  rock has air pockets and very rough feel EX: Pumice & Scoria

How do you classify Igneous Rocks? 1.Texture = Coarse, Fine, Glassy, Pyroclastic 2.Mineral Composition = color of rock A. Light = white, clear, light pink, light gray B. Intermediate = equal parts black & white (salt & pepper) or dark pinks and dark grays C. Dark = Black

Igneous Rock Identification Chart MINERAL COMPOSITION DarkIntermediateLight TEXTURESTEXTURES CoarseGabbroDioriteGranite FineBasaltAndesiteRhyolite GlassyObsidian PyroclasticScoria Pumice

Sedimentary Rocks: Formed from compacted/cemented sediments –Weathering = process that breaks down rocks into sediments –Compaction = process that squeezes or compacts sediments –Cementation = process where smaller dissolved minerals are deposited between sediments/rocks “glues” pieces together

2 Types of Sedimentary Rocks: 1. Clastic = made of weathered & broken pieces of rock 2. Chemical = form when dissolved minerals precipitate (separate) from water EX: lake totally dries up during the summer

How are Sedimentary Rocks classified? 1.Type = Clastic vs. Chemical 2.Texture = grain size (coarse  fine) 3.Composition = minerals (chemical sed. rocks only)

Sedimentary Rock Identification Charts Clastic Sedimentary Rocks TextureRock Name Coarse/GravelConglomerate Medium/SandSandstone Fine/MudShale Chemical Sedimentary Rocks CompositionTextureRock Name CalciteVery CoarseCoquina CalciteCoarseFossiliferous Limestone CalciteMediumLimestone GypsumFineRock Gypsum HaliteFineRock Salt Organic MatterMedium/FineCoal

Metamorphic Rocks: Form when pre-existing rocks are changed by heat and/or pressure –Occurs during mountain building, volcanic activity, etc…

2 types of Metamorphic Rocks 1. Contact = when magma forces its way into cracks/ layers of rock - Rise in Temperature only - Small changes to surrounding rocks 2. Regional = occurs during large scale mountain building (EX: 2 continental plates colliding) - Extreme rise in Temperature & Pressure - Large changes to surrounding rock - Rock usually becomes layered

How are Metamorphic Rocks classified? 1.Composition of parent material 2.Texture = layered vs. non-layered  The longer a rock is metamorphosed, the more layered its appearance (i.e. the longer it has been cooked, the more obvious layers it has)

Metamorphic Rock Identification Chart Parent RockTextureRock Name ShaleVery Fine LayersSlate Fine LayersPhyllite Medium LayersSchist Coarse LayersGneiss LimestoneNO LayersMarble SandstoneNO LayersQuartzite

Ch. 3 Final Assignment Worth 25 points ! Pg , 2, 4, 5, 8 = write out questions and answers 14, 17, 19, 21, 22 = write out answers only, in complete sentences Vocabulary Words CementationMetamorphic Rock Chemical Sed. RockPyroclastic Clastic Sed. RockRegional Met. CompactionRock Contact Met.Rock Cycle ExtrusiveSedimentary Rock Igneous RockWeathering Intrusive

SS #8 Put the date and SS # 8 on your paper. Copy the question & answer it. What is the Rock Cycle?