Download 2. Plate tectonics

Joy of Science
Experience the evolution of the Universe,
Earth and Life
• 
• 
• 
• 
Review
Introduction
Main contents
Quiz
Unless otherwise noted, all pictures are taken from wikipedia.org
Review 1
— 
Which is not included in objects of the solar system?
A. Sun
B. Quasars
C. Moons
D. Comets
E. Asteroids
F. Planets
Review 1
— 
Which is not included in objects of the solar system?
A. Sun
B. Quasars
C. Moons
D. Comets
E. Asteroids
F. Planets
Review 2
— 
Which of the following is the largest planet?
A. Neptune
B. Jupiter
C. Uranus
D. Saturn
E. Mars
Review 2
— 
Which of the following is the largest planet?
A. Neptune
B. Jupiter
C. Uranus
D. Saturn
E. Mars
Review 3
— 
Which of the following is a terrestrial planet?
A. Mars
B. Neptune
C. Saturn
D. Uranus
E. Jupiter
Review 3
— 
Which of the following is a terrestrial planet?
A. Mars
B. Neptune
C. Saturn
D. Uranus
E. Jupiter
Review 4
— 
A small piece of space debris that reaches the surface of the Earth
is (another name for it is “shooting star” or “falling star”)
A. a meteor
B. a meteorite
C. an asteroid
D. a comet
Review 4
— 
A small piece of space debris that reaches the surface of the Earth
is (another name for it is “shooting star” or “falling star”)
A. a meteor
B. a meteorite
C. an asteroid
D. a comet
Review 5
— 
The small rocky bodies found in a broad band between Mars and
Jupiter are
A. meteorites
B. meteors
C. asteroids
D. comets
Review 5
— 
The small rocky bodies found in a broad band between Mars and
Jupiter are
A. meteorites
B. meteors
C. asteroids
D. comets
May 18, 2012
The Earth
- Experience the evolution of the Earth:
the restless Earth
Today’s Keywords
volcano, earthquake, plate tectonics,
mantle convection, plate boundaries,
seismology
Introduction
1. Introduction
Recall the structure and formation of the solar system!
—  After the most of Earth’s mass have accumulated in the beginning,
- Heavy, dense materials sank under gravity toward the center
of the earth
- Lighter, less-dense materials floated to the top
à Let us take a closer look at Earth’s internal structure
— 
Other terrestrial planets also have a distinctively layered structure
by the result of the process represented above
— 
Only Earth has dynamic and restless activities originated by energy
from the hot, dense core
à What dynamic aspects of the Earth are there?
à What is the theory to explain Earth’s dynamic features?
1. Introduction
Inner structure of the Earth
From the center of the Earth,
—  Core: iron and nickel metal
- Inner core: over 5000 deg. C temperature, very high pressure,
solid state
- Outer core: lower pressure, liquid state
— 
Mantle: Charged elements of oxygen, silicon, magnesium, and iron.
Much denser forms of similar composition to surface rocks
due to high pressure. Dense fluid of rocks.
— 
Crust: Made of lightest materials. Less than 10 km thickness in
parts of the oceans, as much as 70 km beneath parts of the
continents. We think of it as a sold surface of Earth.
1. Introduction
Inner structure of the Earth: Picture
Atmospheric
structure
1. Introduction
Dynamic aspects of Earth
— 
— 
— 
The case of disappearing mountains
Volcanoes and Earthquakes
Movements of continents
àPrimary continental model on Earth: Pangaea
1. Introduction
Primary continent on Earth: Pangaea
1. Introduction
Evolution of continents on Earth from
Pangaea
2. Plate tectonics
Plate Tectonics: a unifying View of Earth
Plate Tectonics
—  Compelling model of dynamic Earth
—  Explains many of Earth’s large-scale surface features and related
phenomena
Central idea of the theory
—  Earth’s surface is broken up into some large pieces called tectonic
plates
—  Earth plate is composed of Crust and part of upper Mantle
—  Ocean plates: 8-10 km thickness with dense rock
Continent plates: average 35 km thickness with lower dense rock
2. Plate tectonics
Tectonic Plates
Plates
—  a
2. Plate tectonics
Mantle Convection: continents move as a result of the
forces generated by mantle
— 
Mantle
Earth behaves something like a giant spherical stove, with
burners
on the inside and circulating rocks bringing the heat
core
convection
volcanoes,
to the surface!
earthquakes,
movement of
continents
Effects of mantle convection to Earth’s plates
The top of mantle rocks encounter relatively thin, week plates
à Along oceanic ridges brittle plates crack
à Lava erupts
à Seafloor spreading starts
à All other plates motions start
— 
2. Plate tectonics
Mantle Convection: picture
2. Plate tectonics
Plate Boundaries: determine much of geological
character of Earth’s surface
1. 
Divergent plate boundaries
2. 
Convergent plate boundaries
3. 
Plate transform boundaries
Plate Boundaries
1. Divergent plate boundaries
—  Spreading zone of crustal formation
—  Motion of magma pushes two adjoining
plates farther away from each other.
Results are,
1) A chain of mountains formed by
volcanic motions
2) New pate materials produced by
newly erupted melted materials
3) Shallow earthquakes with low energy
2. Plate tectonics
Plate Boundaries
2. Convergent plate boundaries
— 
Continent - Continent
— 
Ocean – Ocean
— 
Ocean – Continent
2. Plate tectonics
2.2. Plate Boundaries
2. Convergent plate boundaries
Continent - Continent
: two continents collide and ride
on top of both
à high, jagged mountain chain
— 
Ex) The Himalayas 2. Plate tectonics
2.2. Plate Boundaries
2. Convergent plate boundaries
Ocean – Ocean: both plates converge
à Deep ocean trench
à Melted materials become magma,
then rise up to the surface
à Eruptions of lava build a chain of
volcanic islands adjacent to the trench
— 
2. Plate tectonics
2.2. Plate Boundaries
2. Convergent plate boundaries
Ocean – Continent
: denser oceanic plate converge into
beneath continental plate, continental
material is crumpled into coastal
mountains.
— 
à  volcanic mountains parallel to
coast, trench
2. Plate tectonics
2. Plate tectonics
Plate Boundaries
3. Plate transform boundaries
—  Two plates slide each other
not smoothly
Results are,
1) Earthquake
2) No mountain building
3) No volcanic activities
2. Plate tectonics
Plate Boundaries
3. Plate transform boundaries
—  Two plates slide each other
not smoothly
Results are,
1) Earthquake
San Andreas 2) No mountain building
Fault in
3) No volcanic activities
California
San Andreas Fault from
Google maps
3. Volcanism
Plate and Volcanism
— 
Divergent plate boundaries: Main source of new crustal formation
along volcanic spreading ridges
— 
Convergent plate boundaries: Volcanoes are common near
subduction zones. “(Pacific) Ring of Fire” is a dramatic string of
volcanoes.
— 
Hot spots: Chimney like columns of rising hot rocks from lower
mantle or even the core-mantle boundary (cf. bubbles coming to the
surface in water being heated on a stove). A chain of volcanoes is
formed as a tectonic plate slowly moves over a fixed hot spot (ex. the
Hawaiian islands)
3. Volcanism
Plate and Volcanism
— 
Convergent plate boundaries: Volcanoes are common near
subduction zones. “(Pacific) Ring of Fire” is a dramatic string of
volcanoes.
— 
Hot spots: Chimney like columns of rising hot rocks from lower
mantle or even the core-mantle boundary (cf. bubbles coming to the
surface in water being heated on a stove). A chain of volcanoes is
formed as a tectonic plate slowly moves over a fixed hot spot (ex. the
Hawaiian islands)
3. Volcanism
Plate and Volcanism
— 
Hot spots: Chimney like columns of rising hot rocks from
lower mantle or even the core-mantle boundary (cf. bubbles
coming to the surface in water being heated on a stove). A
chain of volcanoes is formed as a tectonic plate slowly moves
over a fixed hot spot (ex. the Hawaiian islands)
Hawaiian Islands
Hot spot
3. Volcanism
Plate and Volcanism
— 
Hot spots: Chimney like columns of rising hot rocks from
lower mantle or even the core-mantle boundary (cf. bubbles
coming to the surface in water being heated on a stove). A
chain of volcanoes is formed as a tectonic plate slowly moves
over a fixed hot spot (ex. the Hawaiian islands)
Picture taken
http://library.thinkquest.org
Hawaiian Islands
Hot spot
4. Earthquake
Earthquake
— 
— 
— 
— 
— 
Earthquakes may be felt near any plate boundary.
Minor shallow ones occur near divergent plate boundaries as two
plates move apart.
Strong earthquakes occur near subduction zones. (many of
Japan’s)
Earthquakes along the transform plate boundaries in the USA.
Occasional ones in the middle of plates
è The origins of these earthquakes are still not fully understood!
5. Seismology
Seismology: exploring Earth’s interior with earthquakes
The idea of seismology
Some of waves of vibrational energy travel through Earth’s
center, others move along the surface, and still others
bounce off layers deep within the planet.
— 
5. Seismology
Seismology: exploring Earth’s interior with earthquakes
5. Seismology
Two principal seismic waves
P-wave (Primary: longitudinal)
: Travel through any time of material at speed of sound
S-wave (Secondary: transverse)
: Typically follows P-wave. Travel only through solids at usually 60%
of speed of P-wave.
Quiz 1
— 
The energy for the movement of tectonic plates comes from
A. the Sun
B. outer space
C. the mantle
D. the crust
Quiz 1
— 
The energy for the movement of tectonic plates comes from
A. the Sun
B. outer space
C. the mantle
D. the crust
Quiz 2
— 
A subduction zone is characteristic of
A. a fault zone
B. a transformed plate boundary
C. a divergent plate boundary
D. a convergent plate boundary
Quiz 2
— 
A subduction zone is characteristic of
A. a fault zone
B. a transformed plate boundary
C. a divergent plate boundary
D. a convergent plate boundary
Quiz 3
— 
The subsurface molten material in the mantle that enters a volcano
is called
A. crustal material
B. fault flow
C. magma
d. lava
Quiz 3
— 
The subsurface molten material in the mantle that enters a volcano
is called
A. crustal material
B. fault flow
C. magma
d. lava
Quiz 4
— 
The study of earthquake waves is called
A. continentalism
B. seismology
C. geology
D. volcanism
Quiz 4
— 
The study of earthquake waves is called
A. continentalism
B. seismology
C. geology
D. volcanism
Next class is on
Earth cycles: Chapter 14