Rock types and rock cycle

What is a Ro c k?
 Naturally-occurring

mixtures of
minerals, mineraloids (no crystals), or
organic matter.


Types of Rocks…


The three main kinds of rock are
igneous, sedimentary and
metamorphic rock.
– Igneous rock: forms when
magma/lava cools and hardens
– Sedimentary rock: forms when
sediments are buried,
compacted & cemented together
– Metamorphic rock: forms when
existing rock is subjected to
great heat & pressure over a
long period of time


What is the diffe re nc e
be twe e n a ro c k and a
mine ral?

 Rocks

are made up of ONE or MORE
minerals.


Onc e a ro c k is fo rme d, do e s it
s tay the s ame ro c k fo re ve r?
 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


What is the pro c e s s thro ug h
whic h ro c ks c hang e ?
 The

Rock Cycle—earth materials change
back and forth among the different
types of rocks

 No

set path a rock takes to become
another kind of rock


IGNEOUS
Weathering, Erosion,
Compaction,
Cementation

Recrystallization

Melting,
Solidification

Melting,
Solidification

Recrystallization

METAMORPHIC

S EDIMENTARY
Weathering, Erosion,
Compaction,

Cementation


Ho w are ro c ks re dis tribute d?

 The

core, mantle, & crust are one giant
rock recycling machine




“Ignis” = Latin for “fire”



Formed from the cooling of either magma or lava



The most abundant type of rock



Classified according to their origin and composition



Igneous Rocks come from magma/lava cooling

down.


ORIGIN— Where rocks are formed
 Below

ground = from magma (intrusive
igneous rock)
 Usually

have LARGE crystal grains (they cooled
slowly) Cooling could have taken hundreds of
years.


Some have large & small crystals
(called porphyritic)


 Above

ground = from lava (extrusive
igneous rock)
 Usually

have SMALL or NO crystals (they
cooled too quickly)


Granite: Intrusive or

Extrusive? Why?


Obsidian: Intrusive or
Extrusive? Why?


COMPOS ITION— What kind of

substances or minerals are rocks made of


Basaltic Igneous Rocks —made

from lava/magma that is low in silica, rich
in iron and magnesium. Rocks are darkcolored.


Granitic Igneous Rocks—made
from magma/lava high in silica
and oxygen. Rocks are lightcolored.


Andesitic Igneous Rocks—
have a composition between
basaltic and granitic.


Diorite-has course grains

Basalt-no course grains


Granite