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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