Rock Formation

Main Concept: Rocks are made from Minerals

• Rocks are nothing more than a mixture of different mineral crystals.

Quartz + Biotite + Feldspar =

Granite

This is Continental Crust!!!

***All three minerals are combined in a Granite rock

(mineral) (mineral) (mineral) (Rock)

Rocks are made from Minerals

• Rocks are nothing more than a mixture of different mineral crystals.

Pyroxene + Olivine = Basalt

This is Oceanic Crust!!!

***Both minerals combined make Basalt

(mineral) (mineral) (rock)

Rock ClassificationGeologists classify rocks into three major groups depending on how they are formed:

Igneous rock, Sedimentary rock, and Metamorphic rock.

There are three types of rock: Igneous Rocks

• Formed from cooled Lava and Magma

can become

***When the lava cools and turns into a solid, it can turn into Basalt!

Liquid lava

As an Example:

Frozen lava

6

Igneous Rock Recipe

5. Igneous Rock Serve and Enjoy

2. Place in oven (2,000 C) Add Heat Energy & Melt

+ HeatMinerals

Quartz + Biotite + Feldspar

1. Take some Minerals & Gasses – Mix well

4. Remove from heat, let it Cool & Crystallize (Intrusive/Extrusive)

3. Change Rock to Liquid Phase (Magma)

There are two types of Igneous Rock:

1)Intrusive

• Formed inside the crust/mantle. • These types always have large

visible crystals. (cooled slowly) • Ex: Granite and Gabbro

This is a special kind of Granite called: “Pink Granite”

***Notice that both rocks have easy to see crystals

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How Intrusive Igneous Rocks Form

• When magma from below rises up, but does not make it to the surface, the minerals start to crystallize slowly and form large crystals.

Volcanic Neck

There are two types of Igneous Rock:

2) Extrusive

• Formed on top of the crust.

• Small, hard to see crystals (cooled quickly)

• Ex: Pumice, Obsidian

***No visible crystals in either rock

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How Extrusive Igneous Rocks Form

• When magma from below rises and punches through, the minerals don’t have time to crystallize – therefore, they produce rocks with small crystals.

Magma(inside)

Lava Flow(Outside)

The lava will quickly cool into solid rock!

Blam!Ash, Gasses, Minerals,

Volcanic glass, etc.

Lava flows out and covers the surface

Other types of rock are

blasted out

• “Granite” and “Rhyolite” form from the same type of cooled magma.

• If the magma cools rapidly, smaller crystals form and “Rhyolite” rock is produced.

• If the magma cools slowly, larger mineral crystals form and the type of rock known as “Granite” forms.

Granite: can you see crystals?

Rhyolite: can you see crystals?

There are no visible crystals!

There are lots of visible crystals!

There are three types of rock: Sedimentary Rock

• Formed by sediments (pieces of rock, shells, and dead organisms) becoming “cemented” (stuck) together.

CoalLimestone

Sandstone

Conglomerate

***You can see lots of different stuff stuck together in these rocks!

Sedimentary Rock Recipe 1. Start at the

Surface

4. Sedimentation & Deposition

5. Compaction & Cementation

2. Weather (Break Up)

3. Erode (Carry Away)

Sediments worn away gather here!

Igneous rock

Layers of sand and sedimentsRain moves sand, dirt, and

rocks down to the ocean

Weathering & Erosion

Sedimentation& Deposition

Compaction

“Cementation” (stuck together)

Sediments, minerals and rocks

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Physical Properties of Sedimentary Rock

rock that is glued to other rock

Take notice of small pieces of rock stuck

together

Conglomerate Rock Notice the rounded rocks glued in this rock. This is from rocks that have been

eroded in a river bed.

Breccia Notice the jaded rocks glued

in this rock. This is from rocks that have been

involved in flash floods.

How to identify:

• Particles of shells/rocks – stuck together

• Dull (not shiny)

• Straight layers

• Fossils (often)

The layers are going in this directioncan you see them?

Sandstone: pieces of sand stuck together

Metamorphic Rocks

• To “Morph” means to change it!“…more than meets the eye!”

• Rocks that have changed after being buried DEEP underground. The heat and pressure from being deep underground changed the rocks.

• They were once Igneous or Sedimentary rocks, but not anymore.

• Has large, inter-grown crystals in thin “bands” (Foliated) or clusters (Non-Foliated).

Metamorphic Rock Recipe1. Get some pre-formed rock –

Igneous or Sedimentary will do & burry it deep underground.

2a. Add a mild amount

of Heat

(Not too hot)

Note: Add more heat for Igneous Rock

2b. Squeeze to Foliate

3. Cool & (Re)-Crystallize

4. Metamorphic Rock

Gneiss (foliated)

Granite(Igneous)

+ H

EA

T

+ Pressure + Pressure

Foliation

• Mineral crystals aligned in parallel layers.

Notice that the crystals have been squished into

mostly straight lines.

Pressure and Heat lead to Metamorphic Rocks

Crystals are large Crystals have become “squished”

The “playing cards” represent mineral crystals in a rock!

The shoes represent the pressure caused by all the rock above

the crystals

Granite=large, randomly located crystals

Gneiss=smaller, lined up crystals

Crystals are Random in

their locations

Crystals line up in

mostly straight lines

becomes

HEAT

Pressure

Foliated v. Non Foliated

• Geologists classify metamorphic rocks according to the arrangement of the grains that make up the rocks.

Foliated (curvy thin crystal lines - Gneiss)

Non Foliated (No lines - Quartzite)

Examples of Metamorphic Rock:

• Gneiss:

• Schist:

• Slate:Can you see all the

straight layers of crystals?