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Geology
Ch. 10 13th edition
Ch. 14 17th edition
Geological Structure
Earth’s internal
Structure
The Earth is a Dynamic Planet
What is geology?
- Dynamic processes taking place on earth’s
surface and in earth’s interior
Layers of the Earth
The Four Layers
The Earth is
composed of
four different
layers.
The Four Layers
1. crust –
relatively thin
rocky outer
skin.
The Four Layers
Two Types of Crust
A. Continental Crust
- Made of many rock
types
- Average 35
kilometers (22 miles)
thick
- Less dense than
oceanic crust
The Four Layers
Two Types of Crust
B. Oceanic Crust
- Igneous Rock:
Basalt
- 7 kilometers (5
miles thick)
- More dense
The Crust
The crust is composed of two rocks. The continental
crust is mostly granite. The oceanic crust is basalt.
Basalt is much denser than the granite. Because of
this the less dense continents ride on the denser
oceanic plates.
The Lithosphere
The crust and the upper layer of the
mantle together make up a zone of
rigid, brittle rock called the
Lithosphere.
The Lithospheric Plates
The crust of the Earth is broken into many
pieces called plates. The plates "float" on the
soft, semi-rigid asthenosphere.
The Four Layers
-
2. Mantle
Semisolid rock
Molten slush cable of
slow movement over
time
Most of earth’s mass
Contains: Iron,
Magnesium,
Aluminum, Silicon, &
Oxygen
The Earth is like a
Hard Boiled Egg
The Four Layers
2. Mantle
- Upper Mantle
- Lithosphere
- Athenosphere
- Lower Mantle
The Asthenosphere
The asthenosphere is
the semi-rigid part of
the middle mantle that
flows like hot asphalt
under a heavy
weight.
Convection Currents
The asthenosphere
"flows" because of
convection currents.
Convection currents are
caused by the very hot
material at the deepest
part of the mantle rising,
then cooling and sinking
again --repeating this
cycle over and over.
The Four Layers
3. Outer Core
- Liquid
- Super Hot
- Mainly – sulfur
and iron.
- Generates
Earth’s magnetic
field
- 2270 Km
The Four Layers
4. Inner Core
- Solid
- Iron & Nickel
- Very Hot
- High Pressure
- 1216 Km
The Four Layers
Eight Most Common
Chemical Elements (%)
WHOLE EARTH
CRUST
Iron 33.3
Oxygen 45.2
Oxygen 29.8
Silicon 27.2
Silicon 15.6
Aluminum 8.2
Magnesium 13.9
Iron 5.8
Nickel 2.0
Calcium 5.1
Calcium 1.8
Magnesium 2.8
Aluminum 1.5
Sodium 2.3
Sodium 0.2
Potassium 1.7
Features of the Crust
Volcanoes
Abyssal hills
Abyssal
floor
Oceanic
ridge
Abyssal
floor Trench
Folded
mountain belt
Craton
Abyssal
plain
Oceanic crust
(lithosphere)
Continental
shelf
Continental
slope
Continental rise
The Earth’s Major Tectonic Plates
EURASIAN PLATE
NORTH AMERICAN
PLATE
JUAN DE FUCA
PLATE
ANATOLIAN PLATE
CHINA
SUBPLATE
CARIBBEAN PLATE
PACIFIC PLATE
COCOS
PLATE
ARABIAN PLATE
AFRICAN PLATE
INDIA PLATE
SOUTH AMERICAN
PLATE
NAZCA PLATE
PHILIPPINE
PLATE
PACIFIC
PLATE
AUSTRALIAN PLATE
SOMALIAN
SUBPLATE
SCOTIA PLATE
ANTARCTIC PLATE
Divergent plate
boundaries
Convergent plate
boundaries
Transform faults
Fig. 14-4, p. 349
The Earth Beneath Your Feet is
Moving!
• Convection Currents
• Tectonic Plates
Spreading
center
Ocean
trench
Subduction zoneOceanic crust
Oceanic crust
Continental crust
Continental
crust
Cold dense
Material cools as
material falls back
it reaches the
through mantle
outer mantle
Mantle
convection cell
Two plates move towards
each other. One is
subducted back into the
mantle on a falling
convection current.
Hot
material
rising
through
the
mantle
Mantle
Hot outer
core
Inner
core
Fig. 14-3, p. 348
Mantle Movement Causes Plate
Movement
Plate Tectonics
• Theory explaining the movement of
tectonic plates and the processes that
occur at their boundaries
– More commonly referred to as “continental
drift” theory
– Plates slide across surface of earth & can
break or collide
– Plate Boundary = area where 2 plates meet
Reykjanes
Ridge
EURASIAN PLATE
JUAN DE
FUCA PLATE
CHINA
SUBPLATE
PHILIPPINE
PLATE
Transform
fault
NORTH
AMERICAN
PLATE
PACIFIC
COCOS
PLATE
PLATE
Transform
fault
East Pacific
Rise
INDIAN-AUSTRLIAN PLATE
MidIndian
Ocean
Ridge
Southeast Indian
Ocean Ridge
MidAtlantic
Ocean
Ridge
EURASIAN
PLATE
ANATOLIAN
PLATE
CARIBBEAN
PLATE
ARABIAN
PLATE
AFRICAN
PLATE
SOUTH
AMERICAN
PLATE
Carlsberg
Ridge
SOMALIAN
SUBPLATE
Transform
fault
Southwest Indian
Ocean Ridge
ANTARCTIC PLATE
Convergent
plate boundaries
Plate motion
at convergent
plate boundaries
Divergent ( ) and
transform fault (
boundaries
)
Plate motion
at divergent
plate boundaries
Types of Plate
Boundaries
• Divergent Boundaries
• Convergent Boundaries
• Transform Fault Boundaries
Wash your hands!
Candy Continents
• Use the tip of the plastic spoon to make
5 or six cracks along and across the
top of your candy bar
• Cracked pieces of chocolate represent
the Earth’s Crustal plates.
Divergent Boundary *
• Also called spreading center
• As plates move apart, new material
(magma) from below fills in the cracks
creating new crust
Divergent Boundary
• Upwelling creates new seaflooor –
called seafloor spreading
Divergent Boundary
Divergent Boundary
• Occurs Along
– Ocean basins at mid ocean ridge
Divergent Boundary
• Examples:
– East African Rift Valley
– Mid-Atlantic Ridge
Convergent Boundary *
• Plates crash into one another
• Also called subduction zones
• One plate is pulled below another
Convergent Boundary
• Results in subduction OR mountain
building
• Occurs Along: Plate Boundaries
Convergent Boundary
• Types
1. Oceanic + Continental
2. Oceanic + Oceanic
3. Continental + Continental
Convergent Boundary
Convergent Boundary
• Oceanic - Continental
Example: ANDES
Convergent Boundary
• Oceanic – oceanic example
The Marianas Trench
is a deep trench
created as the result
of the Philippine Plate
subducting under the
Pacific Plate.
Convergent Boundary
• Continent – Continent Example:
– San Andreas Fault, CA
Transform Fault Boundary
• Plates slide past one another
• Plates grind past each other and
release energy
• Earthquakes may occur along fault
boundaries as plates slide past one
another
• Also called sliding boundary
Transform Fault Boundary
Transform Fault Boundary
Example
• San Andreas Fault
Fault Boundaries
Some Parts of the Earth’s Surface
Build Up and Some Wear Down
• Internal Geologic Processes
– Generally build up the earth’s surface
• External Geologic Processes
– Weathering
• Physical, chemical, and biological
– Erosion
• Wind, flowing water, human activities, glaciers
Ring of Fire
Volcanoes
Earthquakes
Volcanoes
Occurs where magma reaches the earth’s
surface
• Fissure
• Magma
• Lava
Extinct volcanoes
Eruption cloud
Ash flow
Ash
Acid rain
Lava flow
Mud flow
Landslide
Central
vent
Magma
conduit
Magma
reservoir
Fig. 14-6b, p. 351
Volcanic Locations
• Subduction Zones = Pacific Basin Ring
• Spreading Centers (Ocean Ridges) = iceland
• Hot Spots = rising plume of magma that flowed from
crack in crust, Hawaiian Islands
Earthquakes are Geological
Rock & Roll Events!*
Earthquake
Form as stress buildup from plate
movement
– Seismic waves
– Focus
– Epicenter
– Magnitude
– Amplitude
Earthquakes
Energy builds up & is released as
seismic waves ~ vibrations
Occur along fault lines at transform fault
boundaries
Can be gradual or sudden
Seismograph Measures
Earthquakes
• Richter scale
–
–
–
–
–
–
Insignificant: <4.0
Minor: 4.0–4.9
Damaging: 5.0–5.9
Destructive: 6.0–6.9
Major: 7.0–7.9
Great: >8.0
• Largest recorded earthquake: 9.5 in Chile in 1960
Liquefaction of recent
sediments causes buildings
to sink
Landslides may
occur on hilly
ground
Two adjoining plates
move laterally along the
fault line
Earth movements
cause flooding in
low-lying areas
Shock waves
Epicenter
Focus
Fig. 14-7a, p. 351
Earthquake Risk in the United States
Figure 16, Supplement 8
World Earthquake Risk
Figure 17, Supplement 8
Earthquakes
• Primary Effects
– shaking
• Secondary Effects
– Rockslides, fires, & flooding
– tsunamis
Tsunami
• Tidal wave
Travels several hundred miles per hour
Earthquake in seafloor swiftly
pushes water upwards, and
starts a series of waves
Waves move rapidly in
deep ocean reaching
speeds of up to 890
kilometers per hour.
As the waves near land they
slow to about 45 kilometers
per hour but are squeezed
upwards and increased in
height.
Waves head inland
causing damage in
their path.
Undersea thrust fault
Upward wave
Bangladesh
India
Myanmar
Thailand
Malaysia
Sri Lanka
Earthquake
Sumatra
Indonesia
December 26, 2004, tsunami
Fig. 14-8, p. 352
Tsunami
December 2004: Indian Ocean tsunami
– Magnitude 9.15 and 31-meter waves at
shore
– Role of coral reefs and mangrove
Shore near Gleebruk in Indonesia before
and after the Tsunami on June 23, 2004
Fig. 14-9, p. 353
Rock Cycle Review
Weathering &
Erosion
Igneous Rock
Deposition
Sediments
Cementation &
Compaction
Cooling
Magma
Melting
Heat &
Pressure
Metamorphic Rock
Sedimentary Rock
Burial
Rock Cycle
• Cycle of creating, destruction, and
metamorphosis
– Three major rock classifications
• Igneous
• Sedimentary
• metamorphic
Minerals & Rocks
• Minerals
– Naturally Occuring
– Crystalline Structure
– Inorganic
– Solidx
• Rocks – solid, cohesive, aggregate of
one or more crystalline minerals
Deposition
Transport
Erosion
Lithification Sedimentary Rock
Shale, Sandstone,
Limestone
External Processes
Heat,
Pressure
Weathering
Internal Processes
Igneous Rock
Granite, Pumice,
Basalt
Heat,
Metamorphic Rock
Pressure
Slate, Quartzite,
Marble
Magma
(Molten Rock)
Igneous
• Formed from magma cooled
underground or cooled after a volcano
erupts
• quicker cooling leads to smaller
crystals
Sedimentary
• Formed from particles of other rocks
(called sediment) that are worn off
other rocks
• -the sediment get turned into rock by
being buried and compacted by weight
of rocks or by being cemented together
by materials that have been dissolved
in water
Metamorphic
• rocks formed when other rocks are
exposed to great heat AND/OR
pressure
• -pressure and heat can come from
being buried deep in the earth or from
proximity to magma
External Earth Processes
• Weathering – breakdown of solid rock
– Mechanical (Physical) weathering
• Frost wedging, freeze thaw cycle
– Chemical Weathering
• Oxidation (losing/gaining e-)
• Hydrolysis (splitting of water)
• Erosion – process by which earth particles are
moved from one place & deposited in another
–
–
–
–
Wind
Water
Ice
gravity