Download Unit 4: Crustal Change

Unit 6: Crustal Change
I
Earthquakes: are a shaking of the
Earths surface.
YouTube - Earthquake Destruction
A. EQ’s occur when rocks break and
shift along a Fault.
(text p. 220, 219, 312-311)
[Diagram: Normal Faults]
o
Examine Rock Motion Along a Fault
Example: San Andreas Fault, California
p.325
1. Focus: the exact location in the
crust where the rocks move. This
may be many miles below the surface.
2. Epicenter: the location on the
surface directly above the focus.
3. Seismic Waves: energy that
moves out in all directions from the
focus.
(text p.219)
[Add to Diagram]
vidclip- Fault lines and earthquakes
B. Types of Seismic Waves
1. Primary or P Waves vibrate
rock the same direction as wave
movement.
Observe animations of earthquake waves.
2. Secondary or S Waves vibrate
rock at right angles to direction of
wave movement.
Observe animations of earthquake waves.
3. Land or L Waves move along
the surface and cause most of the
damage to people and property.
(See text p.224)
[Demo: Slinky]
C. Features of Seismic Waves
1. P Waves travel faster than S
waves.
2. Both P and S waves speed up as
rock density increases.
3. P waves travel through solids
and liquids. S waves travel only
through solids
These facts are used to determine
the structure of the Earths Interior.
Savage Earth Animation: Earthquake!
Examine Earthquake Waves Moving Through the Earth
YouTube - Earthquakes-Hommocks Earth Science Department 0:00-4:40
D. Earthquakes are measured in three
ways:
1. The Richter Scale measures the
height (amplitude) of the waves on a
seismogram.
 An increase of “1”, means Earth
shakes 10X more.
 Used by news reporters, no longer
used by scientists.
2. Moment Magnitude measures
how much rock moves along a fault.
 Estimates energy released by EQ.

Used by scientists. (See text p.227-228)
3. Mercalli Scale measures the effect
of an EQ on people and property. (I-XII)
MODIFIED MERCALLI INTENSITY SCALE
Most recent earthquakes: IRIS Seismic Monitor
E. Earthquake Damage occurs in a
number of ways:
1. Buildings may collapse.
2. Loose Sediments act like
quicksand (liquefaction).
earthquake liquefaction animation - Google Search
3. Gas lines break and ignite
causing fires.
4. Landslides can occur.
5. Underwater landslides can
trigger Seismic Sea Waves or
Tsunami’s. (see text p.230)
vidclip: Tsunami's
Tsunami Visualizations
YouTube - tsunami indonesia 2004
How Shifting Plates Caused the Japan Earthquake - Interactive Feature - NYTimes.com
japan tsunami 2011 - YouTube
Devastating tsunami hits Japan - YouTube
YouTube - Bill Nye the Science Guy - "Earthquake Rumble"
F. The Earths Interior (See ESRT p.10)
1. Crust: outermost level - 2 types:
 Continental Crust
- thicker but less dense.
- Makes up the continents.
- Mainly composed of Granite
 Oceanic Crust
-thinner but more dense.
-Makes up the ocean floor.
-Mainly composed of Basalt
 At the Moho Boundary
-the velocity of both P and S
waves increases.
-This marks the bottom of the
Crust
(See Esrt p.10)
The man who discovered the MOHO:
Mohorovicic Discontinuity - The Moho - GEOLOGY.COM
U.S. Project to drill to the bottom of the crust:
project mohole - Google Image Search
Soviet (Russian) Project to drill to the bottom of the crust:
Kola Superdeep Borehole - Wikipedia, the free encyclopedia
image- Kola superdeep borehole (Russia)
Well to Hell hoax - Wikipedia, the free encyclopedia
2. Mantle: thickest layer
(ESRT p.10)
 Mainly solid with pockets of
magma.
 Upper part (asthenosphere) flows
slowly in convection cells.
 S waves vanish at bottom marking
beginning of the…
3. Outer Core: thought to be
liquid.
Savage Earth Animation: Earthquake!
 Seismic waves refract (or bend)
at the mantle/core boundary.
 This forms
Earthquake Shadow Zones
(places where no waves are
received.)
animation Locating Layers
4. Inner Core: composed of solid
Nickel-Iron Metal.
 Composition similar to
meteorites.
 P Wave velocity increases.
Greatest Discoveries in Earth Science : Videos : Science Channel
YouTube - Layers of the Earth
YouTube - Reference Table Page 10
[Practice WS: ESRT p.10]
G. Locating the Epicenter of an
Earthquake:
( see text p.224-225)
1. Seismic Waves are recorded by a
Seismograph (text p.222).
2. The seismic tracing is called a
seismogram (text p.223)
3. Locating an EQ Epicenter:
 Determine the arrival times of
the P and S .
[Diagram]
Ex. P Wave arrival: 9:08:30
S Wave arrival: 9:12:00
 Calculate the difference in the
arrival times of the P and S waves.
Ex. 9:12:00 – 9:08:30 = 3 min. 30 sec.
 Determine the distance to the
epicenter using the ESRT: p. 11
[Demo]
Ex. Distance to epicenter = 2,200 km.
 Using a drawing compass,
construct a circle on a map.
Center it on the city where the data
was recorded.
[diagram]
 Repeat this process 2 more times
for a total of 3 locations / circles.
The point where the circles
intersect is the Earthquake
epicenter.
Ex. Text p.225
Review: 4:27-6:37 YouTube - Earthquakes-Hommocks MS 4:40-9:00
[Lab: Earthquake Epicenters]
Distribute labs
Fill out title page
Determine EQ1 P and S Wave arrivals and Time Difference
Review 6:15-7:11 ESRT p.11- EQ travel time graph
Determine EQ1 distances to epicenter.
Draw Circles and identify epicenter
Determine EQ1 P wave travel times.
Determine EQ2 including origin times.
EQ 3 is extra credit.
Discuss Questions and Conclusion.
Quick review:
http://www.youtube.com/watch?v=b_k6FwcO9XQ&feature=related
View 0:00-6:14 ESRT p.11- EQ travel time graph
II Development of the Theory of Plate
Tectonics
A. Continental Drift
 Alfred Wegener (1912) proposed
that the Earths continents once fit
together into a single supercontinent now called Pangaea.
(See text p.250- drifting continents)
Alfred Lothar Wegener [This Dynamic Earth, USGS]
Supporting Evidence:
1. Coastlines of continents appear
to fit together like a “jigsaw puzzle”.
(see text p.248)
2. Rocks, mineral deposits, and
fossils match on either side of oceans.
(see text p.249, 251)
3. Climate change evidence
indicates the continents have moved.
(see text p.252)
See ESRT p.9
Pangea- history of the Continents
YouTube - the last 400 Million years and the future
YouTube Lesson - Theory of Continental Drift
B. In the 1950’s, scientists
accurately mapped the seafloor.
See text p.398-399
What they discovered:
1. Long chains of volcanoes called
Mid Ocean Ridges, were found on the
ocean floor. (see text p.396-397)
Ex. Mid-Atlantic Ridge
(see text p.401)
Image- Mid Atlantic Ridge
mid atlantic ridge- Iceland
mid atlantic ridge- Iceland 2
mid ocean ridge system
2. The age of seafloor rocks, and
thickness of overlying sediment,
increases as distance from ridge
increases.
[Diagram- seafloor cross-section]
3. Lava rises up in center of rift.
 This forms new ocean crust.
 Old seafloor is pushed to the side.
 This is called Seafloor Spreading.
seafloor spreading animation
seafloor spreading animation 2
Vidclip- The Ocean Floor and Continental Drift
4. Pattern of magnetic polarity
reversals match on both sides of ridge.
(See text p.266)
For more, check here:
NOVA | Magnetic Storm | When Compasses Point South | PBS
Or here:
Geomagnetic reversal - Wikipedia, the free encyclopedia
Why does it flip? Check here;
Why Does Earth's Magnetic Field Flip?
seafloor magnetic polarity reversals animation
vidclip- The seafloor is spreading
5.
Other Features of the Seafloor
(See text p.402)
 Continental Shelf
 Continental Slope
 Abyssal Plain
 Deep Sea Trenches (p.261)
III The Theory of Plate Tectonics
explains both Continental Drift and
Seafloor Spreading.
A. The Earths crust is broken into
large sections called Plates.
(see ESRT p.5, text p.256-257)
Bill Nye Greatest Discoveries- Plate Tectonics
YouTube Lesson- Reference Table Page 5-Tectonics Plate Map
(See ESRT p.5)
 On which plate is N.Y. located?
 Which direction is the Cocos plate
moving?
 Which direction is the Pacific plate
moving near the San Andreas fault?
1. Most large EQ’s and Volcanoes
lie along the boundaries of plates.
Ex. “The Ring of Fire” surrounds the
Pacific Ocean bottom.
volcano distribution image
earthquake distribution image
Plate Tectonics Vidclip 1
B. What happens where two plates meet?
(text p.255)
1. Divergent boundaries form
when plates are spreading
apart.
YouTube Lesson - Divergent Plate Boundaries
This forms rift valley’s, mid ocean
ridges, and seafloor spreading.
(text p.259,260, ESRT p.5)
Examples: Mid Atlantic Ridge,
Red Sea
plate boundary animations
2. Transform boundaries form
when plates slide past each
other.
YouTube Lesson - Transform Boundaries and Hot Spots
This may form large faults and strong
EQ’s.
Example: San Andreas Fault
Locate others- ESRT p.5
plate boundary animations
3. Convergent Boundaries
occur when 2 plates collide
head-on.
YouTube Lesson - Convergent Plate Boundaries
Dense oceanic crust may sink down
under less dense continental crust
forming a subduction zone. (text
p.261)
plate boundary animations
Features formed include
 high mountain ranges,
 many EQ’s and volcanoes.
 deep sea trenches,
Example:
West coast of South America: Andes
Mountains, Peru-Chile trench.
Observe an animation of volcanism at a subduction zone.
convergent bondary animations
YouTube - Deep diving in to the abyss
 Ocean crust may collide with
ocean crust forming
Volcanic Island Arc’s
(text p.262, 267)
Examples: Japanese Islands,
Aleutian Islands
convergent bondary animations
 Continental crust may collide with
continental crust forming
extremely high mountains.
Example: Himalaya Mountains
(text p. 262, 263)
convergent bondary animations
C. The driving force of plate
tectonics is Mantle Convection
1. The Plastic Mantle or
Asthenosphere lies under the
crust.
(See ESRT p.10)
 This solid rock flows slowly like
hot tar.
 Rock moves in convection cells
caused by density differences.
 This tugs and pulls on the
overlying plates, making them
move.
[Diagrams]
2. Hot Spots in the crust occur
where a plume of hot magma reaches
the surface in the center of a plate.
As a plate moves over stationary hot
spot, a chain of volcanoes and
seamounts form.
Example: Hawaiian Islands.
(text p.268)
Animation
emperor seamount - Google Image Search