Download C3 Rocks

Chapter
3
Rocks
3.1 The Rock Cycle
Rocks
 Rocks are any solid mass of mineral or
mineral-like matter occurring naturally
as part of our planet.
 A rock is a hard substance composed of
one or more minerals.
• Most common rocks are made
from the most abundant elements
in the Earth’s crust.
• Those elements are:
Oxygen
Aluminum
Iron
Potassium
Silicon
Calcium
Sodium
Magnesium
• http://www.youtube.com/watch?v=pg_jKJF
bA2A
 Types of Rocks
Rocks are placed into groups based upon how they
are formed and texture.
1. Igneous rock
a. Formed when liquid magma cools and
hardens
b. Get their name from the Latin word ignis
– means fire
c. Examples include – granite, basalt,
pumice
Pumice
Granite
2. Sedimentary rock
• Formed from other rocks or minerals
already present on or very near the Earth’s
surface.
• Formed from particles that have been
carried along and deposited by wind and
water. The erosion by wind and water
creates sediments.
• Sediments can be bits of rock like mud,
sand or pebbles. They can also be shells,
bones, leaves, stems and other remains of
living things.
• Sediments become cemented
together to form rocks over time.
• Sedimentary rocks can be formed
as layer of sediments are deposited
on the ocean floor. The layers can
be exposed when seas are drained
or movements in Earth’s crust lift
them up.
• Examples include – sandstone,
shale, breccia, limestone
Sandstone
Shale
Breccia
Limestone
3. Metamorphic rock
• Formed under very intensive heat and
pressure for an extended period of time.
• Formed when chemical reactions,
tremendous heat and/or great pressure
turn existing rock into new kinds of
rocks.
• This process of change may cause the
minerals within the rock to separate into
layers forming distinctive bands.
• The new rocks have physical
and chemical properties that
are very different from the
original rocks.
• Examples include –
quartzite, schist, marble
Quartzite
Schist
Marble
• http://www.youtube.com/watch?v=lE3jR_R
hxO4
3.1 The Rock Cycle
 The continuous changing of rocks from one kind to
another over long periods of time.
 Shows the interrelationships among the three rock
types (igneous, sedimentary, and metamorphic)
 Magma is molten material that forms deep beneath
the Earth’s surface.
 Lava is magma that reaches the surface.
 Weathering is a process in which rocks are broken
down by water, air, and living things.
 Sediment is weathered pieces of Earth elements.
• Rock Formation and Rock Cycle
Animation
• The rock cycle has no definite sequence.
It can follow many pathways.
• All rock begins as magma. The magma is
extruded (forced out) onto the Earth’s
surface and cools or it is cooled within
the Earth.
• http://www.youtube.com/watch?v=53lMdH
zvGCQ
The Rock Cycle
Sedimentary
Rocks
Compacting and
cementing
High temperatures,
great pressure and/or
chemical reactions
Sediments
Weathering and
erosion at the
Earth’s surface
Metamorphic
Rocks
Igneous Rocks
Cooling and
hardening
Melting
Magma
3.1 The Rock Cycle
Energy That Drives the Rock Cycle
 Energy that drives the rock cycle comes from
internal and external (sun) processes
 Processes driven by heat from the Earth’s
interior are responsible for forming both igneous
rock and metamorphic rock.
 Weathering and the movement of weathered
materials are external processes powered by
energy from the sun.
 External processes produce sedimentary rocks.
The Rock Cycle
Under the right conditions, any type of rock can
become another type of rock.
How could metamorphic or igneous rock become
sedimentary rock?
Weathering and erosion break the rocks down into
sediments which over time compact and cement to
form sedimentary rock.
How could metamorphic or sedimentary
rock become igneous rock?
If metamorphic or sedimentary rocks
melt and then cool, they become igneous
rocks.
How could igneous or sedimentary rock
become metamorphic rock?
When igneous or sedimentary rock undergo
extreme heat and/or pressure, they become
metamorphic rock
3.2 Igneous Rocks
•Igneous rocks form from the cooling of molten material.
•Igneous rocks are classified according to their composition and texture.
•Composition refers to the minerals that form the rock.
•Texture is the shape, size, arrangement and distribution of the
minerals.
•Texture and composition are evident in the appearance of the rock.
•Example: Light colored igneous rocks are usually rich in quartz.
•Dark colored igneous rocks are usually rich in augite (dense,
greenish gray)
• http://www.youtube.com/watch?v=mxbmv
G5gpAs
3.2 Igneous Rocks
1. Intrusive igneous rocks
• Magma cooled slowly beneath the
Earth’s surface
• Large crystals form.
• Course grained
• Examples – granite
3.2 Igneous Rocks
2. Extrusive igneous
• Magma reaches the surface by volcanoes
and is cooled there.
• Fine grained because they cool quickly
• Produces small sized crystals
• Also called volcanic rocks
• Examples – obsidian, basalt and pumice
• Pumice is so filled with bubbles that it
can float
3.2 Igneous Rocks
Classification of Igneous Rocks
 Igneous rocks can be classified based
on their composition and texture.
1. Texture
• Coarse-grained texture is caused by slow
cooling resulting in larger crystals.
• Fine-grained texture is caused by rapid
cooling resulting in smaller, interconnected
mineral grains.
Course-Grained Igneous Texture
Fine-Grained Igneous Texture
3.2 Igneous Rocks
Classification of Igneous Rocks
1. Texture (continued)
• Glassy texture is caused by very rapid cooling.
• Porphyritic texture is caused by different rates
of cooling resulting in varied sized minerals.
2. Composition
• Granitic composition rocks are made mostly
of light-colored quartz and feldspar.
Obsidian Exhibits a Glassy Texture.
Porphyritic Igneous Texture
3.2 Igneous Rocks
Classification of Igneous Rocks
2. Composition (continued)
• Basaltic composition rocks are made mostly
of dark-colored silicate minerals and
plagioclase feldspar.
• Andesitic composition rocks are between
granitic light-color minerals and basaltic
composition dark-colored minerals.
• Ultramafic composition rocks are made mostly
from iron and magnesium-rich minerals.
Basalt
 How and where magma cools and the mineral
composition determines the size of a minerals crystals.
 Slow cooling magma produces larger crystals.
 Glassy and fine grained rocks form when lava erupts
from volcanoes and hardens on Earth’s surface.
 Course grained rocks form when molten rock cools
and hardens within the Earth.
Classification of Igneous Rocks
3.3 Sedimentary Rocks
Formation of Sedimentary Rocks
 Weathering, Erosion, and Deposition
• Erosion involves the weathering and the
removal of rock.
• Deposition occurs when an agent of
erosion—water, wind, ice, or gravity—loses
energy and drops sediments.
3.3 Sedimentary Rocks
Formation of Sedimentary Rocks
 Compaction and Cementation
• Compaction is a process that squeezes, or
compacts, sediments.
• Cementation takes place when dissolved
minerals are deposited in the tiny spaces
among the sediments.
• http://www.youtube.com/watch?v=eOuPsJ
wYu9I
3.3 Sedimentary Rocks
Classification of Sedimentary Rocks
 Two Main Groups
1. Clastic sedimentary rocks are composed
of weathered bits of rocks and minerals.
• Classified by particle size
• Common rocks include
- Shale (most abundant)
- Sandstone
- Conglomerate
Shale with Plant Fossils
Conglomerate
http://www.youtube.com/watch?v=202gSE4NBWE
3.3 Sedimentary Rocks
Classification of Sedimentary Rocks
 Two Main Groups
2. Chemical sedimentary rocks form when
dissolved substances precipitate, or
separate, from water.
• Common rocks include
- limestone—most abundant chemical rock
- microcrystalline quartz known as chert, flint,
jasper, or agate
- evaporites such as rock salt or gypsum
- coal
Fossiliferous Limestone
Classification of
Sedimentary Rocks
3.3 Sedimentary Rocks
Features of Some Sedimentary Rocks
 Features of sedimentary rocks are clues
to how and where the rocks are formed
3.4 Metamorphic Rocks
Formation of Metamorphic Rocks
 Metamorphism means “to change
form.”
 Most metamorphic changes occur at
elevated temperatures and pressures.
 Conditions for formation are found a few
kilometers below the Earth’s surface and
extend into the upper mantle.
• http://www.youtube.com/watch?v=e15n7zq0mA
3.4 Metamorphic Rocks
Formation of Metamorphic Rocks
 Contact metamorphism occurs when
magma moves into rock.
• Occurs near a body of magma
• Changes are driven by a rise in temperature.
3.4 Metamorphic Rocks
Formation of Metamorphic Rocks
 Regional metamorphism results in
large-scale deformation and high-grade
metamorphism.
• Directed pressures and high temperatures
occur during mountain building.
• Produces the greatest volume of metamorphic
rock
3.4 Metamorphic Rocks
Agents of Metamorphism
 Heat
• Provides the energy needed to drive chemical
reactions
 Pressure
• Causes a more compact rock with greater
density
Origin of Pressure in
Metamorphism
3.4 Metamorphic Rocks
Agents of Metamorphism
 Hydrothermal Solutions
• Hot water-based solutions escaping from the
mass of magma
• Promote recrystallization by dissolving original
minerals and then depositing new ones
3.4 Metamorphic Rocks
Classification of Metamorphic Rocks
 Two main categories
1. Foliated Metamorphic Rock
• Has a banded or layered appearance
2. Nonfoliated Metamorphic Rock
• Does not have a banded texture
Classification of
Metamorphic Rocks
Gneiss Typically Displays a
Banded Appearance
Marble—A Nonfoliated
Metamorphic Rock