Transcript Geology part 2 2014 Teacherx

1
GEOLOGY
I LIKE TO MOVE IT MOVE IT
Part 1 Age of Earth and scientific classification
Part 2 Plate tectonics
CONTINENTAL DRIFT
Theory
1912 Alfred Weagner proposed the theory that Earth's crust is
slowly drifting on a liquid core.
His theory was not accepted in his lifetime...but now there is a
lot of evidence
National Geographic Continental Drift
http://www.youtube.com/watch?v=3uBcq1x7P34
Pangea
250 million
____________________years
ago
Evidence
Fit of continents
Evidence
Distribution of rocks &
mountains
Evidence
-Paleoclimates- Rocks deposited at the Earth's surface
(sedimentary) reflect the climate and latitude of which they form
-Glacial sediments
-_____________
fossils
Plate Movement

“Plates” of lithosphere are moved around by
the underlying hot mantle convection cells
Questions:
What evidence is there for the continents to be one land
mass called Pangaea?
What causes continents to move?
Unit 1-Spheres
of the Earth
Divergent Boundaries

Spreading ridges


new material erupted to fill the
As plates move apart _________________is
gap
Effect: Underwater mountains
Age of Oceanic Crust
Courtesy of www.ngdc.noaa.gov
Evidence: Earth’s Magnetic Field



The magnetic field is caused by the movement of
liquid iron in the outer core as the planet rotates.
Behaves like a _____________________
near
permanent magnet
center of Earth
Magnetic north (compass measures) differs from
geographic north of planet’s axis of rotation.
How can it be monitored?



Basaltic lava with iron minerals act like compasses.
When they cool, they are magnetized in the
direction of the surrounding magnetic field.
_________________
Paleomagnetism = Study of ancient magnetism
Earth’s Magnetic Field
http://nsdl.org
Magnetic North is NOT at the North Pole
http://nsdl.org
AND…the Magnetic Field
Reverses
• Field reverses ~1 time
every
200,000 years
___________________on
average.
• 400 times in last 330 million
years.
• Last reversal was 780,000
years ago.
NORMAL
REVERSE
Questions:
Is a compass always going to point north?
How does the magnetic field relate to plate tectonics?
Unit 1-Spheres
of the Earth
WHICH FAULT IS AT FAULT?!
What is a fault?
A fault is a fracture in the Earth's crust that occurs when stress is
applied to quickly or when stress is too great.
It can be either _________________________
vertical or horizontal
A vertical fault is comprised of a footwall and a hanging wall
Normal Fault
Tension pulls rocks apart causing the hanging wall block to be pulled
down.
Normal ______________
does not mean most common!
Reverse Fault
_______________of
the normal fault
Opposite
Compression pushes rocks together and causes the hanging wall to be
pushed up
Strike-Slip Fault
A strike-slip fault happens when rocks ____________________
slide past
each other (shearing)
Moves left or right laterally with very little horizontal movement
Questions:
What are the three types of faults?
What are the differences in how these faults move?
Unit 1-Spheres
of the Earth
EARTHQUAKES
Earthquakes

Earthquake is the vibration of Earth caused by a
rapid release of energy
caused by _____________along
a break in
slippage
Earth’s crust
 Often

Focus & Epicenter
 Focus
is point w/in Earth where earthquake starts
 Energy is released in waves
 Epicenter is location on surface directly above the focus
Causes of Earthquakes

San Francisco
Scientists studied 1906 ______________quake
along San Andreas fault
 Some
areas moved 4.7 m on one side of fault
compared to the other
 Hypothesis was developed – force causes rocks to bend
& store elastic energy, eventually friction which holds
rocks together is overcome, rocks slip at the weakest
point (focus) releasing energy allowing rocks to return
to original shape
Causes of Earthquakes

Elastic
_______________rebound
hypothesis
 Explains
that when rocks are deformed, they bend then
break, releasing stored energy
 Most earthquakes are produced by the rapid release
of elastic energy stored in rock that has been subjected
to great forces
 When strength of rock is exceeded, it suddenly breaks,
causing vibrations of an earthquake

Aftershocks & foreshocks
smaller
are ______________earthquakes
produced after a major earthquake
 Foreshocks are small earthquakes produced before a
major earthquake; can be days or years before quake
 Aftershocks
Longitudinal Waves
compression
A longitudinal wave and is created by ____________.
Demo: push slinky, compressing the coils…
back & forth
Any individual particle simply moves
____________________!
The following animation and many other wave animations in this unit courtesy of Dan Russell from Kettering
University: http://www.kettering.edu/~drussell/demos.html
Transverse Waves
When the disturbance and resulting motion of the
perpendicular the motion of the
medium is _______________to
wave, it is called a transverse wave and is created by
tension
__________.
•Demo: stretch slinky by shaking back and forth
•Animation:
•Animation:
Transverse
Stadium Wave
Seismic or Earthquake waves
Earthquakes produce both transverse and
longitudinal waves
• Longitudinal waves in the ground are compression
waves. They travel the fastest, and thus, reach the
primary waves
surface first. So, they are called _________
p
(or __-waves).
They do the least amount of
damage.
Compressions
Expansions
Undisturbed Medium
• Transverse waves in the ground are “shear”
waves. They travel slower, and are thus, called
s
__________ waves (or __-waves).
They do more
secondary
damage than the p-waves.
It is known that p-waves travel farther than
s-waves. Why might that be?
Since we know that transverse
__________ waves
liquids this
cannot travel through _________,
provides evidence that the earth has a
liquid core.
__________
Using a seismograph, the _________________
time difference from
when the p-wave arrives to when the
s-wave arrives can be measured. Knowing the
speed of the two waves through the earth, the
________
distance to the epicenter (starting point) of the
________
earthquake can be determined.
Seismograph
Locating the Epicenter of an Earthquake
3 different
__
3 different seismographs at __
locations are required to find the location of
the epicenter.
epicenter
= seismograph
station
If each seismograph station calculates the
distance from itself to the epicenter, then the
location of the epicenter is the intersection
___________ of
spheres created.
the _________
Ring of Fire

Earthquake zones
95%
 _______of
earthquakes occur in narrow zones
 Most on outer edge of Pacific called circum-Pacific belt
 Second belt Mediterranean-Asian belt
Emergency Situations




What should you do in an Earthquake?
If Indoors
DROP to the ground; take COVER by getting under a sturdy table or other
piece of furniture; and HOLD ON until the shaking stops. If there isn’t a
table or desk near you, cover your face and head with your arms and
crouch in an inside corner of the building.
Stay away from glass, windows, outside doors and walls, and anything that
could fall, such as lighting fixtures or furniture.

If Outdoors

Stay there.

Move away from buildings, streetlights, and utility wires.

Once in the open, stay there until the shaking stops. The greatest danger
exists directly outside buildings, at exits and alongside exterior walls.
Questions:
What causes Earthquakes?
Where are most Earthquakes located? Why?
Unit 1-Spheres
of the Earth
TSUNAMIS
Tsunamis


Wave caused by ____________
earthquake on ocean floor
Causes of tsunamis
 Slab
of ocean floor is displaced vertically along a fault
 Vibration can also set an underwater landslide into
motion
 Waves travel 500-950 km/hr
 Height in ocean is less than 1m but can reach 30m when
it hits land
Tsunamis

Tsunami warning system
 Tsunami
warning center in Honolulu HI
 Receives
info about large earthquakes in Pacific
 Use water level in tide gauges
 Warnings are issued w/in 1 hr of report
 Only ___________________tsunamis
per year
1-2 destructive
Emergency Situations






What should you do in a Tsunami?
Follow the evacuation order issued by authorities and evacuate
immediately. Take your animals with you.
Move inland to higher ground immediately. Pick areas 100 feet (30 meters)
above sea level or go as far as 2 miles (3 kilometers) inland, away from
the coastline. If you cannot get this high or far, go as high or far as you can.
Every foot inland or upward may make a difference.
Stay away from the beach. Never go down to the beach to watch a
tsunami come in. If you can see the wave you are too close to escape it.
CAUTION - If there is noticeable recession in water away from the shoreline
this is nature's tsunami warning and it should be heeded. You should move
away immediately.
Save yourself - not your possessions.
Remember to help your neighbors who may require special assistance infants, elderly people, and individuals with access or functional needs.
VOLCANOES
Vulcan- Roman God of Fire
What is a volcano?


Volcano- Areas of earth’s surface through which
magma and volcanic gases pass
Volcano comes from the Roman word Vulcan, which
fire
means “_______”
What’s inside a volcano?



Magma Chambermolten rock that
feeds a volcano
Vents- cracks in the
crust
What is the
difference
between magma
and lava?
How and why do volcanoes erupt?


buoyant
Hot, molten rock (magma) is ______________(has
a lower
density than the surrounding rocks) and will rise up through
the crust to erupt on the surface.
When magma reaches the surface it depends on how easily it
flows (viscosity) and the amount of gas (H2O, CO2, S) it has in
it as to how it erupts.

__________
Large amounts of gas and a high viscosity (sticky)
magma will form an explosive eruption!

__________
Small amounts of gas and (or) low viscosity (runny)
magma will form an effusive eruption
Explosive Eruptions





Explosive volcanic eruptions
can be catastrophic
Erupt 10’s-1000’s km3 of
magma
Send ash clouds >25 km into
the stratosphere
Have severe environmental
and climatic effects
Hazardous!!!
Mt. Redoubt
Above: Large eruption column and ash
cloud from an explosive eruption at Mt
Redoubt, Alaska
Volcanic Hazards






Courtesy of www.swisseduc.ch
Pyroclastic flow
Lahars/Mud flows
Pyroclastic fall
Lava flow
Noxious Gas
Earthquakes
Effusive Eruptions

Effusive eruptions are
characterised by outpourings of
lava on to the ground.
Hawaii
Courtesy of www.swisseduc.ch

http://i.imgur.com/kLfA5ol.gif
Direct measurements
of pyroclastic flows
are extremely
dangerous!!!
Pyroclastic Flow


Hot, fast moving, high
particles concentration
flows of
gas, rock, and ash
___________________
For example, eruption of
Vesuvius, Italy in 79 AD
destroyed the city of
Pompeii
Pompeii (79AD)
On August 24, 79AD Mount Vesuvius literally
blew its top, erupting tonnes of molten ash,
pumice and sulfuric gas miles into the
atmosphere. Pyroclastic flows flowed over the
city of Pompeii and surrounding areas.
Pompeii (79AD)
Pyroclastic flows of poisonous gas and hot
volcanic debris engulfed the cities of Pompeii,
Herculaneum and Stabiae suffocating the
inhabitants and burying the buildings.
Pompeii (79AD)
The cities remained buried
and undiscovered for almost
1700 years until excavation
began in 1748. These
excavations continue today
and provide insight into life
during the Roman Empire.
Vesuvius today

Naples
Vesuvius remains a
hazardous volcano with
heavily populated flanks:

Vesuvius
Bay of
Naples


Courtesy of www.swisseduc.ch
around 1.5 million
people live in the city of
Naples alone
Naples is situated
approx. 30 km from
Vesuvius
Pyroclastic flows can
flow up to 100 km from
source!
Mt Peleé, Martinique (1902)

An eruption of Mt Peleé in 1902 produced a
pyroclastic flow that destroyed the city of St. Pierre.
before
after
29,000 people died….
Only 2 survived! Why?
Pyroclastic Flow - direct impact
Courtesy of www.swisseduc.ch
Pyroclastic Fall
• Ash load
–
–
–
–
Collapses roofs
Brings down power lines
Kills plants
Contaminates water
supplies
– Respiratory hazard for
humans and animals
Lava Flow

It is not just explosive volcanic activity that can be
hazardous. Effusive (lava) activity is also dangerous.
So….
How do we minimize the risk of active
volcanoes?
*Volcano Monitoring
Volcano Observatories
are set up on all active
volcanoes that threaten
the human population.
These are designed to
monitor and potentially to
predict the eruptive
behaviour of the volcano
in question.
Questions:
What causes volcanoes?
Is lava the only thing to worry about with volcanoes?
Unit 1-Spheres
of the Earth