Rocks
Composed of a mixture of
minerals
Three types of Rocks
Three types of Rocks:
 Igneous- cooling and hardening of hot
molten rock.
 Sedimentary- Pressed and cemented layers
of sediments. Include-rock fragments, plant
&animal remains, or chemicals.
 Metamorphic- Pre-existing rocks changed to
new rock by heat & pressure. No melting
occurs.
ROCK CYCLE
Shows how rock changes from 1 type to
another.
 Classified by how they are formed.
 If the rock melts it will start the cycle
again and be an igneous rock.

IGNEOUS ROCKS
How they are
formed?
 1. formed by cooling
of molten rock.
a. magma-below the
surface.
b. lava- above the
surface.
Will Rock Melt?
Three factors that affect whether rock melts
include:
 Temperature- different minerals have different
melting points, as temperature increases and
other minerals melt, magma composition
changes
 Pressure
 The presence of fluids in the rock (water)
Classifying Igneous Rocks
Texture - Speed of cooling
a.Coarse grained-large grains,slow
cooling below surface-magma.
 Called Intrusive Igneous Rock.

Classifying Igneous Rocks
Fine grains - smaller grains, fast cooling
above surface(lava)
or glassy texture
 Called Extrusive Igneous Rock.

Classifying Igneous Rocks

Porphyrite- 2
textures, large
crystals in center
surrounded by
small.
 Slow to fast cooling.
Classifying Igneous Rocks

Vesicular texturebubbles due to
gases escaping as it
cooled.
Igneous Rock Composition
Chemical make-up of the magma.
 Felsic - Light color, high in silica(qtz &
feldspar), less dense. -ex: Granite.
 Mafic - dark color from iron and
magnesium, so more dense low in
silica, high in Fe & Mg. ex: Basalt,
Gabbro.
 Which one would flow faster?
Types of Igneous Rocks

Granite - Intrusive,
Felsic: mainly Kfeld, qtz, & mica or
hornblende.
 Basalt - extrusive,
Mafic: high in Fe
and Mg, dark
Types of Igneous Rocks

Obsidian Extrusive, Felsic:
volcanic glass.
 Scoria ExtrusiveVesicular, Basaltic.


Types of Igneous Rocks

Pumice Vesicularcan float in water.
Felsic
 Gabbro - Intrusive,
Mafic.
Types of Igneous Rocks

Diorite - Intrusive,
Intermediate.
 Andesite(Porphyrite), Felsic.
SEDIMENTARY
ROCKS
Cemented & compacted
sediments usually formed
in water
Formation of Sedimentary
Rock
Sorting of sediments by size & shape
Large close to shore, size decreases as
you move out. Flatter, farther carried.
 Compaction: particles pressed together
by weight of layers above. Pore space
based on grain size and amount of
pressure.

Formation of Sedimentary Rocks
Cementation: minerals from water
deposit between large pebbles & sand.
Cement ex. silica,calcite
 Precipitation: Only chemical sed.
rocks.a dissolved material (ex. Salt)
settles out of water.

How they are classified?
Which type of sediments make-up
the rock.
1. Clastic-fragments of other rocks.
2. Chemical - precipitated material
3. Bioclastic(Organic) - remains of
plants and animals.
Types of Sedimentary
Rocks

Conglomerate (Large)Clastic,
Cement. Made of
pebbles,sand &
cement. Formed in
river & stream beds.
Rounded pebbles =
weathering
Types of Sedimentary Rocks

Sandstone (Med.),Clastic,
either cementation
or compaction.
Made of sand
(quartz).Formed
along shallow
continental shelf
areas.
Types of Sedimentary Rocks

Shale - (Small,Flat)
Clastic, Compact
Made of silt & clay.
Formed on ocean
floor on deep
abyssal plain areas.
Types of Sedimentary Rocks

LimestoneChemical or
Bioclastic. Formed
from shells or
precipitation of
CaCO3 (calcite)in
shallow sea areas.
Types of Sedimentary Rock


Rock Salt Chemical. prec. of
salt from saltwater in
isolated sea areas
 Coal - Bioclastic.
Made of plant and
animal remains in
swampy areas
Sedimentary Features

Stratification layering, change in
type of sediments
deposited.
Sedimentary Features

Fossils - plants and
animals buried in
sediments.
Sedimentary Features

Ripple marks(wind)
& Mud Cracks
preserved when
Sedimentary rocks
form.
Sedimentary features

Geodes - crystals in
cavity of
Sedimentary rock.
METAMORPHIC ROCKS



Pre-existing rock changed to another
by heat & pressure.
Causes it to re-crystallize and
compress.
Makes Metamorphic rocks are more
dense and less porous.
Type of Metamorphism
1.
2.
Regional- tectonic activity - mountain
building creates heat & pressure
causing changes in a rock’s minerals.
Contact -heat from magma changes
part of the rock it comes in contact
with. Occurs over small area.
Classified according to
structure

Foliated- visible
layers or bands,
when pressure
flattens original
crystals & pushes
them in layers.
ex - Slate, schist,
gneiss.
Classified According to Structure

Unfoliated - no
layers of crystal.
ex - quartzite, marble.
Types of Metamorphic
Rocks

Slate - foliated,
parent rock - shale,
hard & dense.
Types of Metamorphic
Rocks

Schist - foliated,
visible flakes of platy
minerals, often
formed from
shale or basalt.
 Gneiss - foliated,
usually formed from
granite, coarsely
banded or
streaked.
Types of Metamorphic
Rocks

Marble - unfoliated,
formed from
limestone, reacts
with HCl.
 Quartzite unfoliated, formed
from sandstone.
tough sugary look.