The Rock Cycle

Section 3.2

• Vocabulary to know: • Igneous rock• Magma• Lava• Extrusive igneous

rock• Intrusive igneous rock• Texture• Composition• Silicate

What are igneous rocks?• Igneous rock-

– Form from molten rock deep within the Earth that has cooled… OR…

– From molten rock that has reached the surface and cooled lava

• Temperatures deep within the Earth are hot enough (14000F to 23000F) to melt rock

Where do igneous rocks come from?

• Volcanoes!• Extrusive

igneous rock-– Forms when

lava cools on Earth’s surface

• Intrusive igneous rock-– Forms when

magma cools within the Earth

Textures of igneous rocks• Texture = size of the rock’s mineral crystals• Large crystals- slow cooling time

– Intrusive rocks commonly have large crystals

• Small/No crystals- fast cooling time– Extrusive rocks commonly have small or no crystals

How can you tell the difference between salt and sugar?

Answer = look at their composition!• Igneous rocks are mainly made up of silicate minerals

Ship Rock• Formed 1km below

Earth’s surface• It was once intrusive

igneous rock– It is what’s left behind of

magma that once fed a volcano

• Through weathering and erosion, surface rock has been worn away…

• …Ship Rock survives because igneous rock is usually harder than other types of rocks

Section 3.3

• Vocabulary to know: • Sedimentary rock• Sediment• Cementation• Coal• Limestone• Crossbeds• Ripples

What are sedimentary rocks?• Sedimentary

rock-– Forms from

loose material (sediments) that get pressed together (cemented) into rock

– Sediments-• Can be pieces

of rocks, minerals, plants, or animals

Sedimentary rock formation…• Rainwater washes

away rock particles…• Flow downhill to

streams and rivers…• Eventually these

sediments reach the ocean…

• Settle on the bottom of the ocean…

• Pressure eventually forces these sediments together…

• Sedimentary rock is formed!

Fossils can also make sedimentary rock• Coal-

– Made up of remains of plants (dead wood, bark, leaves, etc.)

– Started forming millions of years ago

• Limestone-– Made up of remains of

ocean organisms (shells, bones, etc.)

– Pressure “squishes” these materials together into rock

Coal formation• A- Dead pieces of

plant matter collecting on lake bottom

• B- sediments applying pressure on top of plant matter

• C- Even greater pressure applied

• D- Coal is created

Limestone towers (Mono Lake)• Minerals can

dissolve in water …• …and then re-form

as the water evaporates

• Often they form underwater…

• …and as the water level drops they become visible

Sedimentary rocks can teach us about the past…

• Crossbeds-– These layers were

once moving sand dunes

• Ripples-– The surface of this

sandstone preserves ancient sand ripples

Section 3.4

• Vocabulary to know: • Metamorphic rock• Metamorphism• Recrystallization• Foliation• Foliated rock• Nonfoliated rock

What are metamorphic rocks?• Metamorphic

rock-– Forms when

heat or pressure cause older rocks to change into new types of rocks

• Metamorphism-– The process in

which existing rock is changed by heat or pressure

Metamorphic rock formation• During

metamorphism rocks undergo many changes

• Heat and pressure can break the bonds that join the atoms in minerals… the atoms then join together differently– Recrystallization

• Rocks do not melt during this process!!!

Foliation• Foliation-

– An arrangement of minerals in flat or wavy parallel bands

• Foliated rocks-– Develop under pressure– Minerals flatten out or

line up in bands

• Nonfoliated rocks-– Develop if rock is made

up of only one type of mineral

– May not be under enough pressure

The Rock Cycle