ROCKS ROCK!
Earth’s Layers
Compare & Contrast Rocks!

Look at the rock samples and write a short
paragraph ( at least 5 COMPLETE sentences)
describing how the rocks are similar and how they
are different.
What is a ROCK?



Solid mass of mineral or mineral-like matter that is
naturally occurring
Most rocks are made up of more than one mineral
Some rocks are made up of no minerals
 Coal=organic
material
Three Major Types of Rocks

Igneous
 Intrusive
 Extrusive


Sedimentary
Metamorphic
The Rock Cycle
Interactions among
Earth’s water, air, &
land can cause rocks to
change from one type
to another
Magma or Lava?


Magma is molten material deep beneath Earth’s
surface
When magma reaches the surface it becomes lava
Important Vocabulary to Understand
the Rock Cycle


Weathering—process by which rocks are physically
and chemically broken down by water, air, & living
things to produce sediment
Sediment—weathered pieces of earth material
What drives the rock cycle?


Igneous and metamorphic rocks are formed by
processes from Earth’s interior heat
Sedimentary rocks are produced by processes on
and near Earth’s surface
 Weathering
and the movement of weathered materials
are external processes powered by energy from the
sun & gravity
Think!


Turn to the person sitting next to you and discuss:
What do you notice about the rock cycle?
IGNEOUS ROCKS!!!
Igneous Rocks


Intrusive igneous rocks—form when magma hardens
beneath Earth’s surface
Extrusive igneous rocks—forms when lava hardens
Quick Check


How are magma and lava the same?
How are they different?
Classification of Igneous Rocks

Coarse Grained Texture
 Slow

cooling=large crystals
Fine Grained Texture
 Fast
cooling=small, interconnected minerals grains
Which is coarse grained & which is fine grained?
Classification of Igneous Rocks

Glass Texture—no time for ions in the lava to
arrange into crystals before hardening
 Randomly

distributed ions
Porphyritic Texture—rocks with very different-size
minerals experience different rates of cooling
Classification of Igneous Rocks

Granitic Composition—light-colored silicate
minerals quartz & feldspar are the main minerals
 Most
granitic rocks contain about 10% dark silicate
minerals (such as biotite mica & amphibole)
Classification of Igneous Rocks

Basaltic Composition—contain many dark silicate
minerals & plagioclase feldspar
 Rich
in magnesium & iron
 Typically darker & denser than granitic rocks because
of the iron
 Make up Earth’s ocean floor
Classification of Igneous Rocks

Andesitic Composition—between granitic & basaltic
 At
least 25% dark silicate minerals, mainly amphibole,
pyroxene, & biotite mica

Peridotite—almost entirely dark silicate minerals
(olivine & pyroxene)
 Ultramafic—rare
upper mantle
at Earth’s surface but much of the
Classification of Major Igneous Rocks
Rock Joke Break!
Sedimentary Rocks!!!
Formation of Sedimentary Rock


Clastic Sedimentary Rocks—made of weathered
bits of rocks and minerals
Chemical Sedimentary Rocks—dissolved minerals
precipitate from water solutions
Clastic Sedimentary Rocks


Made of mostly clay minerals & quartz
Grouped by size of the sediments
 Conglomerate=rounded,
gravel-size or larger particles
 Breccia=angular particles
 Sandstone=sand-sized grains
Chemical & Biochemical Sedimentary
Rocks


Dissolved substances precipitate, or separate, from
water solutions
Water evaporates or boils off leaving a solid
product
 Ex:

limestone, rock salt, chert, flint, and rock gypsum
Biochemical Sedimentary Rocks=shells & skeletal
remains of organisms that settle to the ocean floor
Features of Sedimentary Rock


Each layer of sedimentary rock records a period of
sediment deposits
Fossils are unique to some sedimentary rock
Classification of Sedimentary Rocks
Metamorphic Rocks!!!
Formation of Metamorphic Rocks


Existing rocks are changed by heat & pressure
What does metamorphism mean?
 Come
up with the best definition possible with the
person next to you!
 Changes form
Formation (Continued)


Contact morphism=magma intrudes (forces its way
into) rock
Marble often forms when magma intrudes into
limestone
Formation (Continued)

Regional metamorphism
 Large
areas of rocks are subjected to extreme
pressures & temperatures during mountain building
 Intense changes occur at a large scale level
Agents of Metamorphism

Heat
Provides energy needed to drive chemical reactions
 Cause existing minerals to recrystallize
 Magma & change in temperature from depth


Pressure (stress)
Increases with depth
 Causes the spaces between mineral grains to close
 Results in more compact rock with a greater density


Reactions in solution
Hot solutions promote recrystallization
 Can deposit new minerals in the rocks

Classification of Metamorphic Rocks

Foliated metamorphic rocks
 Layered

or banded appearance
Nonfoliated metamorphic rocks
 No
banded texture
 Most contain only one mineral
 Marble is an example—made up of calcite
Classification of Metamorphic Rock
Think!

Use what you have learned about the rock cycle to
explain the following statement:
 One

rock is the raw material for another rock
Your friend shows you a rock with distinct layers.
How can you and your friend determine if the rock
is a sedimentary rock of a metamorphic rock?