Transcript oceanic crust - Duluth High School

Geology and Nonrenewable Minerals
chapter 14
Core Case Study: Environmental Effects
of Gold Mining
 Gold producers
•
•
•
•
South Africa
Australia
United States
Canada
 Cyanide heap leaching- controversial
• Extremely toxic to birds and mammals
• Ponds can leak or overflow
• 2000: Collapse of a dam retaining a cyanide
leach pond
• Impact on organisms and the environment
Gold Mine with Cyanide Leach Piles and
Ponds in South Dakota, U.S.
GOLD IN GEORGIA
 Has been found in 37 counties
 1829-1933 The gold rush started near
Dahlonega. By 1940, gold was harder to find
and many miners left for California
14-1 What Are the Earth’s Major
Geological Processes and Hazards?
 Concept 14-1A Gigantic plates in the earth’s
crust move very slowly atop the planet’s mantle,
and wind and water move the matter from place
to place across the earth’s surface.
 Concept 14-1B Natural geological hazards
such as earthquakes, tsunamis, volcanoes, and
landslides can cause considerable damage.
The Earth Is a Dynamic Planet
 What is geology? (dynamic processes that occur
on the Earth’s surface and in its interior)

http://ngm.nationalgeographic.com/video/player#/?titleID=how-big-is-7billion
 Three major concentric zones of the earth
• Core – solid inner core and liquid outer core
• Mantle
• Including the asthenosphere – partly melted rock
that flows
• Crust
• Continental crust
• Oceanic crust: 71% of crust
Planet Earth: Lithosphere
 Lithosphere - Earth’s crust and upper mantle
 Thickness varies from 10 to 200 km
1. Oceanic crust – floor of deep ocean basins
- Composed of basalt (igneous). Also iron,
magnesium and calcium.
- Thin (4-5 km) and young.
2. Continental crust -- forms continents.
- Composed of granite (igneous). Also silicon,
aluminum, sodium and potassium.
- Thickness 35 to 70 km.
- Old crust.
The Lithosphere
The crust and the upper layer of the mantle
together make up a zone of rigid, brittle rock
called the Lithosphere.
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 Mantle
The Mantle is the
largest layer of the Earth.
The middle mantle is
composed of very hot
dense rock that flows like
asphalt under a heavy
weight. The movement of
the middle mantle
(asthenosphere) is the
reason that the crustal
plates of the Earth move.
Convection Currents
The middle mantle
"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.
Convection Currents
The next time you heat anything
like soup or water in a pan you can
watch the convection
currents move in the liquid.
When the convection currents flow
in the asthenosphere they also
move the crust. The crust gets a
free ride with these currents, like
the cork in this illustration.
The Outer Core
The core of the
Earth is like a ball
of very hot metals.
The outer core
is so hot that the
metals in it are all
in the liquid state.
The outer core is
composed of the
melted metals of
nickel and iron.
The Inner Core
The inner core of
the Earth has
temperatures and
pressures so great
that the metals are
squeezed together
and are not able to
move about like a
liquid, but are forced
to vibrate in place
like a solid. (Ni, Fe,
Au, Pt and U)
Let’s Review!
• What are the 3 concentric zones of the
earth?
• CRUST, MANTLE AND CORE
• What is the main rock that comprises the
continental crust?
• GRANITE
• What is the main rock that comprises the
oceanic crust?
• BASALT
• The crust and upper mantle make up the
_____.
• LITHOSPHERE
• What makes the crustal plates move?
• CONVECTION CURRENTS
• The layer of the mantle that flows and is
responsible for these convection currents
is the _____.
• ASTHENOSPHERE
Volcanoes
Abyssal hills
Abyssal Oceanic
ridge
floor
Abyssal
floor Trench
Folded
mountain belt
Craton
Abyssal
plain
Oceanic crust
(lithosphere)
Mantle
(lithosphere)
Continental
Continental
shelf
slope
Continental
rise
Continental crust (lithosphere)
Mantle (lithosphere)
Mantle
(asthenosphere)
Fig. 14-2, p. 346
The Earth Beneath Your Feet Is
Moving (2)
 Three types of boundaries between plates
• Divergent plates
• Oceanic ridge and continental rift valleys
• EX: Mid-Atlantic Ridge, East Pacific Rise, East
African Great Rift Valley
• Convergent plates
• Subduction, subduction zone
• Trench
• EX: Cascade Mt Range (Ca to Wa- Mt. St.
Helens)
• Transform faults
• Sliding of plates past each other
• EX: San Andreas Fault
Spreading center
Ocean
trench
Subduction
Oceanic crust Oceanic crust
zone
Continental
crust
Continental crust
Material cools Cold dense
as it reaches material falls
the outer back through
mantle
mantle
Mantle Hot material
rising
convection
through the
cell
mantle
Two plates move
towards each other.
One is subducted back
into the mantle on a
falling convection
current.
Mantle
Hot outer
core
Inner
core
Fig. 14-3, p. 346
EURASIAN PLATE
JUAN DE
FUCA PLATE
NORTH
AMERICAN
PLATE
CARIBBEAN
PLATE
ANATOLIAN
PLATE
CHINA
SUBPLATE
AFRICAN
PLATE
PACIFIC
PLATE
COCOS
PLATE
NAZCA
PLATE
Divergent plate boundaries
PACIFIC
PLATE
SOUTH
AMERICAN
PLATE
SOMALIAN
SUBPLATE
SCOTIA
PLATE
PHILIPPINE
PLATE
ARABIAN
PLATE INDIA
PLATE
AUSTRALIAN
PLATE
ANTARCTIC PLATE
Convergent plate
boundaries
Transform faults
Fig. 14-4, p. 347
PLATES
• Move at about the rate a fingernail grows
• Mountains, earthquakes and volcanoes
occur at plate boundaries
• Divergent- ridges in ocean/rifts on land
• Convergent- subduction/trenches in
oceans and mountains (orogonic belt) on
land
• Transform fault- 2 plates slide past one
another (San Andreas Fault)
The San Andreas Fault as It Crosses Part
of the Carrizo Plain in California, U.S.
Mount Everest
Base Camp
Himalayas
Khumbu Icefall
Mount Everest
 Mt Everest- tallest mountain on land (29,029 ft =
8848 m) 1.6-3.9 (4-10 cm) inches higher every
year
 Everest is part of the Himalaya mountain range
along the border of Nepal and Tibet.
 At 9,800 feet, for example, there's about 2/3 of
the oxygen in the air than at sea level. At 20,000
ft, there is roughly half the oxygen content in the
air. At 29,035ft, the summit of Everest, there is
only a third of the oxygen in the air.
 At the summit, the temperature can be 100°F
below zero. But on a good summit day, a climber
can expect around -15°F
 On May 29, 1953, Tenzing
Norgay Sherpa of Nepal &
Edmund Percival Hillary of
New Zealand climbed to
the summit of Everest via
the Southeast Ridge Route
 http://www.youtube.com/watch?feature=endscre
en&NR=1&v=56nWTyDTLZc
Divergent boundaries
 Africa’s Great Rift Valley
 The oceanic ridge is a continuous submarine
mountain chain extending approximately 80,000
km (50,000 miles) through all the world’s oceans
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 (driven by the
sun and influenced by gravity)
• Weathering (key in soil formation)
• Physical, Chemical, and Biological processes that
break down rock
• Erosion
•
•
•
•
Wind
Flowing water
Human activities
Glaciers- (formed the Great Lakes)
Parent material
(rock)
Biological
weathering
(tree roots
and lichens)
Chemical
weathering
(water, acids,
and gases)
Physical
weathering
(wind, rain,
thermal expansion
and contraction,
water freezing)
Particles of parent material
Fig. 14-6, p. 348
Volcanoes Release Molten Rock from
the Earth’s Interior
 Volcano
• Fissure- vent or crack
• Magma
• Lava
 1980: Eruption of Mount St. Helens (Mount Pinatubo)
 1991: Eruption of Mount Pinatubo- Philippines
 Benefits of volcanic activity- forms mountains,
lakes (Crater Lake, OR), fertile soils
Extinct
volcanoes
Eruption cloud
Ash flow
Ash
Acid rain
Lava flow
Mud flow
Landslide
Central vent
Magma conduit
Magma reservoir
Fig. 14-7, p. 349
Earthquakes Are Geological Rock-andRoll Events (1)
 Earthquake
• Seismic waves- vibrations caused by
earthquakes
• Focus
• Epicenter
• Magnitude – amount of energy released
• Amplitude – size of seismic waves
Earthquakes Are Geological Rock-andRoll Events (2)
 Richter scale – a logarithmic scale recorded
by a seismograph. Measures the amplitudes
of the waves produced. An earthquake of
magnitude 5 has 10X more ground shaking
than a magnitude of 4. It is the energy though
that knocks down buildings and causes
damage. A magnitude of 5 releases 32X more
energy than a magnitude 4 eq.
•
•
•
•
•
•
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
Earthquakes Are Geological Rock-andRoll Events (3)
 Foreshocks and aftershocks
 http://earthquake.usgs.gov/learn/animations/animation.php?fla
sh_title=Foreshocks%2C+Mainshocks%2C+and+Aftershocks+F
lash+Animation&flash_file=aftershock&flash_width=400&flash_
height=275
 Primary effects of earthquakes
Due to the shaking and the resulting damage to
buildings/infrastructure and due to loss of life or injury, land
displacement
 Secondary effects
Rock slides, flooding, liquefaction of sediments, fires, and
tsunamis
 Reduce damage by mapping faults, strengthening
building codes, preparing emergency teams, storing
supplies and educating the public
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
Focus
Epicenter
Fig. 14-8, p. 350
Areas of Greatest Earthquake Risk in
the United States
Areas of Greatest Earthquake Risk
in the World
EQ TRIVIA!
 There are over 1 million eq a year
 There are over 10,000 eq in California a year.
 San Andreas Fault is over 800 miles long.
Earthquakes on the Ocean Floor Can
Cause Huge Waves Called Tsunamis
 Tsunami, tidal wave
 Can travel as fast as a jet plane
 Detection of tsunamis
buoys, pressure recorder
 December 26, 2004: Indian Ocean tsunami
• Magnitude of 9.15 earthquake
• Waves as high as 100 feet, 228,000 were killed
• Coral reefs and mangrove forests reduce wave
impact. (mangrove forests had been cleared and
many reefs have been damaged in last 30 years)
Shore near Gleebruk in Indonesia before
and after the Tsunami on June 23, 2004
 http://www.youtube.com/watch?feature=player_
embedded&v=tUN_UTY0GNo#!
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
Burma
India
Thailand
Earthquake
Malaysia
Indonesia
Sumatra
Sri Lanka
December 26, 2004, tsunami
Fig. 14-11, p. 352
Gravity and Earthquakes Can
Cause Landslides
 Mass wasting
• Slow movement or
• Fast movement
•
•
•
•
Rockslides
Avalanches
Mudslides
1970, earthquake in Peru caused massive
landslide that killed 17,000 people
 Effect of human activities such as forest
clearing, road building and crop growing
increases the frequency of and damage caused
What do you remember??
 What mountains were formed at a convergent
boundary?
 CASCADES AND HIMALAYAS
 How were the Hawaiian Islands formed
 BY A HOT SPOT
 Name a feature at a divergent boundary
 AFRICAN RIFT VALLEY, OCEANIC RIDGE
 Name a famous transform fault
 SAN ANDREAS FAULT

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How are earthquakes recorded?
RICHTER SCALE
What is the tallest mountain on land?
MOUNT EVEREST
Name 3 factors of erosion
WIND, WATER, GLACIERS AND HUMAN
ACTIVITIES
Study the following website. For site #3, take the quiz, save
it as a word document, and send it to me through edmodo.
 http://www.geo.cornell.edu/hawaii/220/PRI/conti
nental_puzzle.html
 http://www.wwnorton.com/college/geo/egeo2/co
ntent/animations/2_6.htm (hotspots)
www.learner.org/interactives/dynamicearth/index.h
tml
14-2 How Are the Earth’s Rocks
Recycled?
 Concept 14-2 The three major types of rocks
found in the earth’s crust—sedimentary,
igneous, and metamorphic—are recycled very
slowly by the process of erosion, melting, and
metamorphism.