Rocks - Trimble County Schools

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What is a rock?

Where do we find rocks?

How are rocks classified?

What is the Rock Cycle?

What is a Rock?

Naturally-occurring mixtures of minerals, glass or organic matter.

Where do we find rocks?

Rocks can be . . .

Hard

Soft

Shiny

Dull

Smooth

Rough

One color

Many colors

Classifying Rocks

Rocks are divided into 3 groups based on how they were formed:

Rocks

Igneous Sedimentary Metamorphic

Igneous Rocks

Igneous Rock is formed when magma or lava cools.

Igneous rock can form:

– underground, where the magma (a hot liquid) cools slowly OR

– above ground, where the magma cools quickly.

Igneous Rocks formed underground

(from lava or magma) usually have

LARGE crystal grains (they cooled

slowly)

Igneous Rocks formed above ground

(from lava) usually have SMALL or NO crystals (they cooled too quickly)

Sedimentary Rocks

Sedimentary Rock is formed from sediments (rock fragments, mineral grains, animal & plant remains) that are pressed or cemented together.

Sedimentary rocks form at or near the earth's surface at relatively low temperatures and pressures

These sediments are moved by wind, water, ice or gravity.

Sedimentary rocks are fossil-carrying rocks. They can be formed underwater, too, and can be made up of bits of shells and skeletons of sea animals.

Metamorphic Rock

Metamorphic Rocks are those that have changed due to intense temperature and pressure.

Metamorphic rocks CHANGE FORM. Both igneous rocks and sedimentary rocks can change into metamorphic rocks

Heat and pressure do not change the chemical makeup of the parent rocks but they do change the physical properties of those rocks. This rock has many layers.

The Life of a Rock

Igneous

Layers of sediment join together.

Sedimentary Rock

Melted rock cools and hardens

Metamorphic

Changes are made from pressure and heat.

Once a rock is formed, does it stay the same rock forever?

NO!

Rocks are continually changed by many processes, such as weathering, erosion, compaction, cementation, melting, and cooling

Rocks can change to and from the three types

Rocks become bigger

, and bigger

, and bigger , and bigger . . .

By earthquakes

By volcanoes

By heat and pressure

Rocks become smaller , and smaller

, and smaller

, and smaller

. . .

By erosion

By wind

By earthquake

By floods

By rain

By mudslides

The Rock Cycle Song

(Sing to the tune of "Row, Row,

Row Your Boat")

SEDIMENTARY rock

Has been formed in layers

Often found near water sources

With fossils from decayers

Then there's IGNEOUS rock

Here since Earth was born

Molten Lava, cooled and hardened

That's how it is formed

These two types of rocks

Can also be transformed

With pressure, heat and chemicals

METAMORPHIC rocks they’ll be.

This rock is formed by cooling magma.

IGNEOUS

This type of rock can be formed underwater. It is made up of bits of shells and skeletons of sea animals.

SEDIMENTARY

This rock is formed by intense heat & pressure.

METAMORPHIC

This rock is formed when tiny grains of sand become cemented together.

 SEDIMENTARY

This rock is formed by quickly cooled lava.

IGNEOUS

IGNEOUS ROCKS

ARE FORMED BY:

Cooling

Magma or

Lava

Sedimentary rocks are formed when tiny grains of

_______ become cemented together.

SAND

Let’s Review

A rock that has many layers, is flat, and comes apart easily is most likely which type?

– A. granite

– B. igneous

– C. metamorphic

– D. sedimentary

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