Earth Materials: Rocks

How can rock cycle rocks
provide information about

events that have occurred over

Earth’s long history?

Types of Rock

IGNEOUS

METAMORPHIC

SEDIMENTARY

The Basic Cycle

• All igneous rocks are

made from molten
rock.

• All sedimentary rocks

are

made

from

weathered products of
other rocks.

• All metamorphic rocks

are the products of
preexisting rocks that
are heated or squeezed
at high temperatures
and/or pressures.

Igneous Rock: Formed by Fire

Magma

Molten
rocks

Lava

Magma
that has
reached

the

surface

Extrusive

Solidified
outside

Intrusive

Solidified

inside

Classification of Igneous Rocks by Color

Felsic

rich in light-

colored
minerals

rich in Si,
Na, Al, and
K and poor
in Fe and

Mg

Intermediate

contain
roughly
equal

amounts of
dark- and

light-colored

minerals.

Mafic

contain
abundant

dark- colored

minerals

rich in Fe,

Mg, and Ca.

Ultramafic

consist almost
exclusively of
Fe and Mg-rich
minerals from

the mantle

rich in Fe, Mg,

and Ca, but
poor in Si.

Igneous rocks are mainly composed of silicates

How can silica influence magma behavior?

What can texture of igneous

rocks tell us?

General rule
Rapid cooling : small crystals
Slow cooling: larger crystals

Sedimentary Rocks:
Compacted and Cemented
Sediment

• The word sedimentary

indicates the nature of
these rocks, for it is
derived from the Latin
sedimentum,

which

means

“settling,”

a

reference to a solid
material settling out of
a fluid.

Sedimentation

Weathering

Transport

Deposition

Compaction

Cementation

2 Sources of
Sedimentary
Rocks

Detrital Sedimentary rocks

"detritus, solid particles
from weathered rocks"

Chemical and Biochemical

Sedimentary rocks

derived from material
(ions) that is carried in

solution to lakes and seas

Geologists use
particle size to
distinguish among
detrital
sedimentary
rocks.

How can particle size
provide

information

about

where

it

is

deposited?

These rocks are derived from material
(ions) that is carried in solution to
lakes and seas.
Chemical and biochemical sediments
are formed from precipitation (settling
out).

Biochemical sediments

Chemical sediments

Coal--an organic sedimentary rock

Features of
Sedimentary
Rocks

As layers of sediments called strata or
beds accumulate, each records the
nature of the environment at the time
the sediment was deposited.

Metamorphic Rock:
New Rock From Old

• Produced from

preexisting igneous,
sedimentary, or even
other metamorphic rocks

• Has a parent rock

Metamorphism

Metamorphism takes place
when preexisting rock is
subjected to a physical or
chemical environment that
is

significantly

different

from that in which it
initially formed.

Can be low-grade or high
grade

What Drives Metamorphism

Heat as metamorphic agent

What Drives Metamorphism

Confining Pressure and differential stress as metamorphic agents

Metamorphic Textures

Low Grade

High Grade

Foliated and
Non-Foliated

Rocks