ROCKS, ROCKS, AND MORE ROCKS!Chapters 5 and 6 (Glencoe Earth Science)

What is a rock?

A rock is a hard substance made of one or more minerals

There are 3 types of rocks: Igneous Sedimentary Metamorphic

What’s an Igneous Rock?

Formed by crystallization of magma Igneous comes from the latin word for fire These rocks are associated with fiery lava

flows Lava is magma that flows on the Earth’s

surface

Types of Igneous Rocks

Extrusive Formed from lava on Earth’s surface that

cooled quickly Known as volcanic rock Fine-grained

Intrusive Formed inside the Earth Magma rises up into pre-existing rocks and

hardens Coarse-grained Called “Plutonic” rocks after Pluto, the god of

the Underworld These rocks commonly produce landforms Granite is most common

Igneous Rocks

Which is the intrusive rock? Which is the extrusive rock?

What About Igneous Rocks?

Useful as building materials Interlocking grainy texture provides

strength Resistant to weathering Granite is especially durable

Used for columns, tiles and countertops, etc. Valuable ore deposits are often

associated with igneous rocks

It’s Sedimentary, Watson!

What’s a sedimentary rock? A rock formed from sediments Sediments are pieces of material that have

been carried/deposited by wind, water, etc. Sedimentary rocks form when these pieces

are cemented together

How do Sedimentary Rocks Form? Weathering

Processes that break rock into smaller pieces Chemical-minerals in rock are dissolved or

chemically changed Physical-minerals are unchanged; rock fragments

break off Erosion

Movement of materials from one location to another Caused by wind, moving water, gravity, glaciers

(ice) Eroded materials almost always moved downhill

Sediments, Classified

Clastic Rock Refers to fragments of rock and minerals

created by weathering and erosion Clastic comes from the Greek word for

“broken” Classified by particle size

Deposition

Occurs when sediments are laid down on the ground or sink to the bottom of a body of water

When wind/water slows down, largest particles settle out first, etc. Smallest particles settle last.

Sediments moved by glaciers and landslides are not sorted.

Burial

Most sediments are deposited in basins (depressions)

As more sediments are deposited, the layers on the bottom are exposed to more heat and pressure.

Causes lithification Physical and chemical processes that turn

sediment into sedimentary rock

Process of Lithification

1-Compaction Weight of sediments forces them closer

together Water is squeezed out of mud Sand resists compaction because of grain-

to-grain contact

Process of Lithification

2-Cementation Temperatures increase Buried sediments can be chemically changed Mineral growth cements sediments together

into solid rock Two types of cementation

A new mineral grows between grains OR The same mineral grows between or over grains

Features of Sedimentary Rock Horizontal layering (bedding)

Graded bedding: particle size becomes more coarse/heavy toward bottom layers

Cross-bedding: formed as inclined layers of sediment move forward across a horizontal surface

Fossils Evidence of once-living organisms

Types of Sedimentary Rock

Clastic Rock Most common; formed from deposits of

loose sediments 1/3 or more is pebble-called conglomerate

Not as common as rock w/ smaller pieces If made with sandy grains-called

sandstones Very common

Particles smaller than sand-called shale

Types of Sedimentary Rock

Chemical Rocks Formed when water evaporates leaving

minerals behind Ex: Rock salt, some limestone

Stalactites, stalagmites

Organic Sedimentary Rocks Formed from remains of a once-living thing Ex: coal

Why are Sedimentary Rocks Important? Energy Resources

Coal, Oil, Natural gas are found in sedimentary rock

Many metals are mined from sedimentary rocks

Used in making cement (limestone) Used in making blocks for walls (sandstone,

limestone)

Metamorphic Rock

Changing one type of rock into another as a result of extreme heat, pressure, and/or chemical reactions

Can be formed from any of the three types of rock

The ‘new’ rocks have different properties than the rock did before the ‘morph’

The Rock Cycle

Continuous changing and remaking of rocks Rocks are constantly being recycled from one type to another

Example of the Path of a Rock Through the Rock Cycle Granite (igneous rock) Wind/rain erodes exposed rock, bits flake off,

carried to bottom of stream carried to river, along with other sediments carried to sea, deposited

Deposits build up form sandstone (sedimentary rock)

Sediments continue to be buried and are under more pressure/higher temps pressed together even more form quartzite (metamorphic rock)AND THE CYCLE CONTINUES…