chapter 4 igneous rocks formation 20122013

Rock ClassificationRocks are divided into three main

classes based on how they form:1. Igneous2. Sedimentary3. MetamorphicEach type of rock can be further

classified based on: Composition and texture

Composition

The chemical make up of the rock or what it is made of.

This can be minerals or other materials: shells, clay, plants, sand, pebbles

Texture/GrainsDetermined by the grains size, shape

and position. Igneous can be fine or coarse grainSedimentary can be characterized by

observing lithified (cemented) inorganic grains, minerals, organic material, or fossil fragments. The wide range of textures common in sedimentary rocks is separated into clastic, chemical, and bioclastic (biochemical) groups.

Texture/Grains

Metamorphic textures consist of two main types: foliated and non-foliated textures.

Texture can reveal the process that formed the rock.

Igneous RocksIgneous Rocks

What are they?What are they?Rock made from cooled Rock made from cooled

–LAVA, above ground or LAVA, above ground or –MAGMA, below groundMAGMA, below ground..

ClassificationClassification

They are classifiedThey are classified in 3 ways:in 3 ways:

1.1.Texture – grain Texture – grain 2.2.Origin - where formedOrigin - where formed3.3.Mineral Composition – Mineral Composition –

made frommade from

Grain Size Grain Size Have….Have….

SPECIAL SPECIAL NAMESNAMES

Texture/GrainTexture/GrainCoarseCoarse Grained = large grains, cooled Grained = large grains, cooled

slowlyslowlyThink about it…. If it cools over a long time – the grains have time to get big! Think about it…. If it cools over a long time – the grains have time to get big!

Most abundant intrusive rock is GRANITE Most abundant intrusive rock is GRANITE

FineFine Grained = small grains, cooled Grained = small grains, cooled fastfastThink about it… If it cools over a short time – the grains don’t have time to get Think about it… If it cools over a short time – the grains don’t have time to get big!big!

BasaltBasalt

Igneous Rock Formation-Igneous Rock Formation-OriginOrigin ExtrusiveExtrusive – formed ABOVE GROUND. – formed ABOVE GROUND.

It cools It cools fastfast so it has so it has smallsmall grains. grains. IntrusiveIntrusive – formed UNDERGROUND. It – formed UNDERGROUND. It

cools cools slowlyslowly so it will have so it will have largelarge grains. grains.

Laccolith

Examples of each type of ROCKFine Grained

Basalt = Extrusive Igneous rock

Course Grained

Granite = Intrusive Igneous rock

Mineral CompositionMineral Composition How much silica is in the magma/lava?How much silica is in the magma/lava?

– Low silica content = dark colored = MaficMafic

– HighHigh silica content = silica content = light light colored = colored = Felsic

High Silica Content Low Silica Content

Felsic Igneous Rock Mafic Igneous Rock

Lighter

Darker

Big Crystals Small or No Crystals

Label the igneous rock Label the igneous rock formationformation

Ticket out: CHOOSE ONLY Ticket out: CHOOSE ONLY ONEONE

What makes up the grains in an igneous rock?

Illustrate grains of an igneous rock and explain why this happens

Compare and contrast intrusive and extrusive igneous rocks