Chapter 4 - Rocks

What can be learned by studying rocks…

We can learn mo better about earth.

So what is a rock???

It’s a mixture of 1 or more minerals. Easy.

The Rock Cycle

• Shows how any rock may be transformed from one type into another.

• It’s a continuous process that causes rocks to change.

Vocab terms

• Magma – underground molten rock

• Lava – above ground molten rock

• Crystallization – formation of minerals from cooling magma/lava

• Weathering – any process that breaks down rocks into smaller pieces (sediment)

Vocab terms

• Erosion – transportation of sediment

• Deposition – accumulation of sediment

• Metamorphism – changing one type of rock into another by heat/pressure/chemicals

• Lithification – compaction and cementation of sediment

Igneous Rocks…from fire

• 2 main types

– Intrusive (large crystals)

• From magma

• Underground

• Cools and forms slowly

– Extrusive (small crystals)

• From lava

• Above ground

• Cools and forms quickly

Igneous Rocks Classification

• 2 ways to classify igneous rocks

1 = Texture 2 = composition

1. Texture (3 types)

a) Coarse grained – slow cooling, large crystals

b) Fine grained – fast cooling, small crystals

c) Glassy – super fast cooling, glassy

Porphyritic – slow and fast cooling, has both large and small crystals

Course-Grained Igneous Texture

Fine-Grained Igneous Texture

Obsidian Exhibits a Glassy Texture.

• 2. Composition

• Granitic (felsic)

– High in silica (SiO4), light colored, lower density

• Basaltic (mafic)

– Low in silica, dark colored, high in iron and magnesium higher density

• Andesitic (intermediate)

• Ultramafic

Sedimentary Rocks

Your teacher rocks!

Sedimentary Rocks

• From (Latin) sedimentum = settling

• Made from sediments of any type

• 4 agents of erosion (transportation)

1. Water

2. Wind

3. Glaciers

4. Gravity

3 Types Sedimentary Rock

1. Clastic = formed from sediment

2. Chemical = formed from precipitation or evaporation…dried up soda on a table

3. Biochemical (organic) = formed from remains of once living organisms

1) Clastic Sedimentary Rocks

• Conglomerate – rounded pebble sized

• Breccia – angular pebble sized

• Sandstone – sand sized

• Siltstone – silt sized

• Shale – clay sized

Conglomerate

2) Chemical Sedimentary Rocks

• Crystalline limestone – precipitates from ocean water

• Gypsum – precipitates from oceans, too

• Travertine – precipitates in caves

• Chert/flint – quartz

• Rock salt – evaporated salt water

3) Biochemical Sedimentary Rx

• Fossil limestone – fossil remains

• Coquina – shells and shell fragments

• Chalk – microscopic shells and clay

• Bituminous coal (B coal) – plant remains

Metamorphic Rocks

• Means to change form

• 2 types of metamorphism

1. Contact

- small areas from toughing hot magma

2. Regional

- large areas from the pressures of mountain building

Agents of Metamorphism

1. Heat (temperature)

2. Pressure (stress)

3. Reactions in hot solutions (chemicals)

Metamorphic Rock Classification

• 2 textures

1. Foliated - layered

2. Nonfoliated – not layered

1. Foliated Metamorphic Rx

A) Slate – very thin layers from shale

B) Phyllite – thin layers, sheen, wavy, from slate

C) Schist – medium layers,shiny, micas, from phyllite

D) Gneiss – distinct black & white layers, from schist or granite

2. Nonfoliated Metamorphic RX

A) Marble – shiny, fizzes in acid, H = 3, from limestone

B) Quartzite – shiny, won’t fizz, H = 6 – 7, from sandstone

C) Anthracite coal – shiny, black, from bituminous coal

The carbon cycle…see page 85

TREE

1. Igneous Rx

A) Intrusive