Download Lecture rocks

Objectives
Identify 3 types of rocks and how they
are classified.
 Determine how each type of rock is
formed

Definition
A naturally
occurring
solid mixture of one or
more minerals
Did you know…..
ths
5/6
That rocks occupy
of
the volume of Earth and
account for 2/3rds of its
mass?
Three types of rocks
Igneous
Sedimentary
Metamorphic
Rocks
are classified based
on how they form
Igneous

Derived from the Latin word ignis,
meaning “fire”

Rocks that form when magma cools and
crystallizes

Examples: Granite, pumice, basalt,
rhyolite, obsidian, gabbro
Classifying igneous rocks

Texture
 Extrusive igneous rocks
○ Form from molten material that has cooled
and crystallized close to or on Earth’s surface
○ Contact with air or water causes material to
cool rapidly
○ Fine-grained or small crystals
○ Ex. Pumice, basalt, rhyolite, obsidian
Classifying igneous rocks

Texture
 Intrusive igneous rocks
○ Magma that pushes into surrounding rocks
and crystallizes underground
○ Cools slowly
○ Large, visible crystals, coarse grained
○ Contain mineral crystals (may contain
valuable minerals and gemstones)
Classifying igneous rocks

Mineral Composition
 Granitic Composition
 Basaltic Composition
 Andesitic Composition
Did you know…
the oldest rocks are meteorites,
more than 4.5 billion years
old, which formed at the same
time as earth?
Sedimentary Rocks

Recycled pieces that form new rock

How is it done?
Sedimentary rock formation
Preexisting
rock
Weathering
Weathering

When rock gets broken into pieces by
the effects of wind, water, ice, changing
temperatures and gravity

Two types of weathering
 Chemical weathering
 Physical weathering
Sedimentary rock formation
Sedimentary rock formation
Deposition

Occurs when the sediment eventually
comes to rest on the ground or sinks to
the bottom of bodies of water

Layers will build up on top of one
another
Sedimentary rock formation
Preexisting rock
Weathering
Sediments
Erosion
Deposition
Compaction and
cementation
Compaction and Cementation

New layers of sediment may be loosely
packed with many air and H2O pockets
The lower layers get squished together
due to the weight and pressure of the
layers above…this pushes out the water
Compaction and Cementation

The dissolved minerals in the water
form crystals between the grains which
holds them together
Sedimentary rock formation
Then the cycle begins
again
Sedimentary Rocks

Examples
 Shale
 Sandstone
 Conglomerate (also called pudding stone)
 Soft coal
 Rock salt
Features of Sedimentary
Rocks

Bedding
 Distinct horizontal layers
 Effects of wind, H20, the sun, and raindrops
can be preserved

Fossils
 Preserved remains or traces of organisms
that once lived
Mud cracks
Ripple marks
A joke…
 Where
night?
do fossils go to bed at
Metamorphic Rock

High temps and/or pressure
 Change the texture, mineral makeup or
chemical makeup of a rock WITHOUT
melting it.
Metamorphic Rock

Regional metamorphism
 When large areas of Earth’s crust are
effected by high pressure and temperature

Contact metamorphism
 When magma comes in contact with solid
rock

Hydrothermal metamorphism
 Hot H20 from volcanic activity