Download Chapter 6 Notes: Rocks

CHAPTER 6 NOTES: ROCKS
Earth Science
6.1 OBJECTIVES
1.
2.
Differentiate among the 3 major
types of rocks.
Compare and contrast the
processes in the rock cycle.
WHAT IS A ROCK?
A
group of minerals bound together.
 Consists largely of 1 mineral or of several
different minerals in different quantities.
 Igneous: formed from the cooling and
hardening of hot, magma from inside
Earth.
 Sedimentary: formed from compaction
and cementing of layers of sediment.
 Metamorphic: formed by the effect of
heat and pressure on other rocks.
THE ROCK CYCLE

The repeated series of events that rocks change
from 1 type to another.
THE ROCK CYCLE
1. Magma is the source of all Earth’s rocks.
2. Cools when it reaches surface = igneous
3. Broken down by weathering forming
sediments
4. Sediments compact and cement together =
sedimentary
5. Gets buried under other sediments and
exposed to high pressure and temp =
metamorphic
6. Crustal movements force rocks deep into
Earth, forming back into magma.
7. Rock cycle begins all over again
6.2 OBJECTIVES
3.
Distinguish between intrusive and
extrusive igneous rocks and how
they form.
IGNEOUS ROCK FORMATION
 Intrusive:
form from underground
magma.
 Form at Earth’s surface (volcanic ash).
 Magma is felsic, mafic, or intermediate
form:
Felsic: thick & slow moving. Large
amounts of silica (SiO2).
 Mafic: hotter, thinner, and more fluid.
Higher amounts of iron, magnesium, and
lower silica.

IGNEOUS ROCK FORMATION CONT.
 Intrusive
rocks = coarse grained
texture b/c of longer cooling time.
 Extrusive rocks = tiny crystals and
fine grained texture. Can be smooth
and glassy.
IGNEOUS ROCK DESCRIPTIONS
 Granite
Family: form from felsic
magmas





Coarse grained
Contain quartz, , feldspar, mica, and
hornblende.
White, gray or pink color from
feldspars
Intrusive
Obsidian, pumice, felsite, rhyolite
IGNEOUS ROCK DESCRIPTION CONT.
 Gabbro
Family: Consists of mafic
rocks.



Dark and denser than granite family
rocks.
Contains pyroxene, olivine, plagioclase
feldspar, biotite
Basalt is the most common rock.
IGNEOUS ROCK DESCRIPTIONS CONT.
Diorite
Family: has
characteristics of both mafic and
felsic.
Medium grays-green colors
Coarse grained member
Andesite
6.3 OBJECTIVES
4.
Distinguish among the 3 types of
sedimentary rocks and how they
form.
SEDIMENTARY ROCKS
Covers most the Earth’s surface.
 Classified by 3 basic formation processes.
1. Clastic rocks: Formed from fragments of
other rocks due to weathering.
o
Fragments moved by H20
o
Minerals fill in spaces between sand grains
= cementation
o
Conglomerate: large fragments
o
Sandstone: small fragments, porous and
permeable
o
Shale: smallest fragments, not porous or
permeable

SEDIMENTARY ROCKS CONT.
Chemical Rocks
o
RockFormed when minerals fall out
of solutions (evaporation or chemical
action).
o
Rock salt (halite), rock gypsum,
limestones
3. Organic Rocks
o
Form from sediments made of plant
& animal remains.
o
Limestone & coal (fossilized plants)
2.
6.4 OBJECTIVES
5.
Explain the processes involved in
the formation of metamorphic
rocks.
METAMORPHIC ROCKS
Formed
from preexisting rocks
called parent rocks.
Metamorphism: the process
where a rock’s structure is
changed by pressure, heat, &
moisture.
2 types: regional & local
METAMORPHIC ROCKS
 Regional
Metamorphism: Large areas of
rock change form after exposure to intense
heat & pressure.
 Local metamorphism: 2 types contact &
deformational
1. Contact: Hot magma moves into rock,
heating it and changing it.
o Causes fewer changes
2. Deformational: Occurs at low temps. &
high pressure caused by stress & friction
METAMORPHIC ROCK DESCRIPTIONS
 Foliation:
the tendency of a rock to
form bands of minerals or split along
parallel layers.
 Sandstone is the parent rock for
quartzite.
 Seashells formed by marine animals
out of carbon and calcium ions form
sedimentary rock limestone, which
becomes marble.