HOW ARE ROCKS CLASSIFIED

Chapter 7 Lesson 2 Pages 274-281

Igneous Rock p. 274 Igneous rock is rock that is formed when

melted rock hardens.

Magma is melted rock inside the Earth.

Lava is melted rock at the Earth’s surface.

Crystallization is the hardening of magma into rock.

Igneous Rock p. 274Intrusive

Intrusive rock cools underground, deep within the Earth’s crust.

Characteristics of intrusive igneous rock: --Intrusive rocks cooled slowly. --Intrusive rocks have large crystals. --These rocks have coarse texture.

Examples: Granite and Diorite

Granite

Diorite

Igneous Rock p. 274Extrusive

Extrusive igneous rock is rock that cools on the Earth’s surface.

Extrusive rock cools quickly on the surface.

Extrusive rock has fine grains or even no crystals at all and

looks glassy

Examples: Obsidian, Pumice and Rhyolite

Obsidian

Igneous

Igneous

Rhyolite

Igneous

Pumice

Sedimentary Rock p. 276

Sedimentary rock is rock that forms when layers of sediment settle and bind together.

There are two main groups of sedimentary rock,

Clastic and Chemical

Sedimentary Rock p. 276Clastic

Clastic-The word comes from the Greek word that means “broken”.

Process begins when rock is broken through weathering.

Wind and water move sediment to new places, layers build up; minerals bind layers.

Layers are pressed and cemented together.

Clastic rocks are classified by size of particle.

Sedimentary Rock p. 276Clastic

Examples of clastic sedimentary rock

Fine particles form shale.

Medium particles form sandstone.

Coarse pebble-sized particles with smooth edges form conglomerates.

Sedimentary

Shale

Sedimentary

Sandstone

Sedimentary

Conglomerate

Sedimentary Rock p. 276Chemical

Chemical sedimentary rocks form when chemicals in water come out of the water (evaporate) and form solids.

Example: Limestone (may contain fossils)

Sedimentary

Limestone

Metamorphic Rock p. 278 - Meta means “change”.

How metamorphic rock is made:

Igneous or sedimentary rock is changed by

PRESSURE

HEAT – high temperature, very hot water

BOTH

Metamorphic Rock p. 278 Metamorphism is the process by which rock

is changed into metamorphic rock.

The main cause is high temperature-deep inside the Earth or in lava/magma.

Minerals melt and then crystalize into new minerals.

Metamorphic Rock p. 278 Regional Metamorphism takes place over a

large area Mountain building

Contact metamorphism changes a smaller area by magma or lava touching rock and changing the rock that was touched.

Metamorphic Rock p. 278 Examples

Shale becomes SLATE.

Slate becomes SCHIST.

Schist becomes GNEISS.

Limestone becomes MARBLE.

Metamorphic Shale becomes SLATE.

MetamorphicSlate becomes SCHIST.

MetamorphicSchist becomes GNEISS.

MetamorphicLimestone becomes MARBLE.

Uses of Rock p. 280

Rock UseGranite BuildingsSandstone GlassObsidian Jewelry, blades (in history)Pumice Cleaning productsShale ConstructionMudstone ConstructionMarble Buildings and sculpturesSlate Roofs, floors, chalkboards