RocksRocks

RocksRocks Naturally occurring solid mixtures of one Naturally occurring solid mixtures of one

or more minerals and organic matteror more minerals and organic matter They can be made of two or more They can be made of two or more

different minerals that have been: different minerals that have been: cemented togethercemented together squeezed and heated together squeezed and heated together melted and cooled togethermelted and cooled together

Types of RocksTypes of Rocks IgneousIgneous SedimentarySedimentary

MetamorphicMetamorphic

Igneous RocksIgneous Rocks Most igneous rocks are produced Most igneous rocks are produced

deep underground by the cooling and deep underground by the cooling and hardening of magma.hardening of magma.

Igneous rocks are classified in three ways:Igneous rocks are classified in three ways: OriginOrigin – where they are formed – where they are formed Composition – Composition – refers to the minerals refers to the minerals

that make up the rockthat make up the rock Texture Texture – the shape, size, arrangement and distribution of – the shape, size, arrangement and distribution of

minerals that make up the rockminerals that make up the rock

OriginOrigin

ExtrusiveExtrusive- Formed from lava; volcanic- Formed from lava; volcanic

Obsidian

Pumice

Granite

Intrusive Intrusive - Formed deep within the earth- Formed deep within the earth

Intrusive Igneous RocksIntrusive Igneous Rocks Intrusive igneous rocks are formed deep Intrusive igneous rocks are formed deep

within the Earthwithin the Earth Granite is the most common (continental Granite is the most common (continental crust)crust)

Intrusive masses named for their size and Intrusive masses named for their size and shapeshape

QuartzQuartz

MicaMica HornblendeHornblende

FeldsparFeldspar

Plutons are large irregularly shaped intrusionsare large irregularly shaped intrusions

Batholiths – Batholiths – largest largest

intrusive bodiesintrusive bodies Stocks – smaller Stocks – smaller areasareas

than batholithsthan batholiths Sills – sheet-like Sills – sheet-like

intrusions parallel intrusions parallel to to

previous layersprevious layers Dikes - sheet-like Dikes - sheet-like

intrusions that cut across previous rock layers at an angleintrusions that cut across previous rock layers at an angle

Intrusive Igneous RocksIntrusive Igneous Rocks

GabbroDiorite

GranitePegmatite

Extrusive Igneous RocksExtrusive Igneous Rocks

• Basalt is the most common (oceanic Basalt is the most common (oceanic crust)crust)

• Formed from lava; Formed from lava; volcanicvolcanic

• Cools quickly and contains very small, Cools quickly and contains very small, or no or no crystalscrystals

• Can erupt from fissures, which are Can erupt from fissures, which are long long cracks in the Earthcracks in the Earth

Extrusive Igneous RocksExtrusive Igneous Rocks

Basalt

Obsidian Pumice

ScoriaAndesite

Rhyolite

CompositionComposition Refers to the minerals that make up the rockRefers to the minerals that make up the rock

MaficMafic

FelsicFelsic light-colored rocks less dense contain elements such as aluminum, potassium, silicon, & sodium

dark-colored rocksdark-colored rocksdenserdenser

rich in calcium, iron and magnesium (poor in rich in calcium, iron and magnesium (poor in silicon)silicon)

Texture – Texture – refers to the shape, size, refers to the shape, size, arrangement and distribution of the arrangement and distribution of the minerals that make up the rockminerals that make up the rock

Rapid cooling = fine-grained with small Rapid cooling = fine-grained with small crystalscrystals Slow cooling = coarse-grained with large Slow cooling = coarse-grained with large crystalscrystals

Fine-grained Fine-grained

Coarse-grainedCoarse-grained

GlassyGlassy

PorphyriticPorphyritic• The size of the crystals depends

on:

TexturesTextures

Obsidian

Granite

Granite

Basalt

Glassy

Fine-grained

Coarse-grained

Porphyritic

Composition and Texture of Composition and Texture of Igneous RockIgneous Rock