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: Igneous = rock made from cooled magma either above or below ground EX: Granite Sedimentary = rock formed from compacted & cemented sediments EX: Limestone 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… - HOWEVER……..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? Texture = Coarse, Fine, Glassy, Pyroclastic 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 Dark Intermediate Light TEXTURES Coarse Gabbro Diorite Granite Fine Basalt Andesite Rhyolite Glassy Obsidian ---------- Pyroclastic Scoria 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? Type = Clastic vs. Chemical Texture = grain size (coarse  fine) Composition = minerals (chemical sed. rocks only)

Sedimentary Rock Identification Charts Clastic Sedimentary Rocks Texture Rock Name Coarse/Gravel Conglomerate Medium/Sand Sandstone Fine/Mud Shale Chemical Sedimentary Rocks Composition Calcite Very Coarse Coquina Coarse Fossiliferous Limestone Medium Limestone Gypsum Fine Rock Gypsum Halite Rock Salt Organic Matter Medium/Fine Coal

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? Composition of parent material 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 Rock Texture Rock Name Shale Very Fine Layers Slate Fine Layers Phyllite Medium Layers Schist Coarse Layers Gneiss Limestone NO Layers Marble Sandstone Quartzite

Ch. 3 Final Assignment Worth 25 points ! Pg. 89-90 1, 2, 4, 5, 8 = write out questions and answers 14, 17, 19, 21, 22 = write out answers only, in complete sentences Vocabulary Words Cementation Metamorphic Rock Chemical Sed. Rock Pyroclastic Clastic Sed. Rock Regional Met. Compaction Rock Contact Met. Rock Cycle Extrusive Sedimentary Rock Igneous Rock Weathering Intrusive

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