Chapter 3 RocksWhy 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 groundEX: 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 grayB. Intermediate = equal parts black & white (salt & pepper) or dark pinks and dark graysC. Dark = Black

Igneous Rock Identification Chart

MINERAL COMPOSITION

Dark Intermediate Light

TEXTURES

Coarse Gabbro Diorite Granite

Fine Basalt Andesite Rhyolite

Glassy Obsidian Obsidian ----------

Pyroclastic Scoria 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?

1. Type = Clastic vs. Chemical

2. Texture = grain size (coarse fine)

3. Composition = minerals(chemical sed. rocks only)

Sedimentary Rock Identification Charts

Clastic Sedimentary RocksTexture Rock NameCoarse/Gravel Conglomerate

Medium/Sand Sandstone

Fine/Mud Shale

Chemical Sedimentary RocksComposition Texture Rock NameCalcite Very Coarse Coquina

Calcite Coarse Fossiliferous Limestone

Calcite Medium Limestone

Gypsum Fine Rock Gypsum

Halite Fine 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?

1. Composition of parent material2. 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

Slate Fine Layers Phyllite

Phyllite Medium Layers Schist

Schist Coarse Layers Gneiss

Limestone NO Layers Marble

Sandstone NO Layers Quartzite

Ch. 3 Final AssignmentWorth 25 points !

Pg. 89-901, 2, 4, 5, 8 = write out questions and answers14, 17, 19, 21, 22 = write out answers only, in complete sentences

Vocabulary WordsCementation Metamorphic RockChemical Sed. Rock PyroclasticClastic Sed. Rock Regional Met.Compaction RockContact Met. Rock CycleExtrusive Sedimentary RockIgneous Rock WeatheringIntrusive

SS #8Put the date and SS # 8 on your paper.

Copy the question & answer it.

What is the Rock Cycle?