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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?