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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. - PowerPoint PPT Presentation
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GEOLOGYI LIKE TO MOVE IT
MOVE ITPart 1 Age of Earth and scientific classificationPart 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
____________________years ago250 million
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
Unit 1-Spheres of the Earth
Questions:What evidence is there for the continents to be one land mass called Pangaea?
What causes continents to move?
Spreading ridges As plates move apart _________________is erupted to fill the gap
Effect: Underwater mountains
Divergent Boundaries
new material
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 center of Earth
Magnetic north (compass measures) differs from geographic north of planet’s axis of rotation.
permanent magnet
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.
_________________ = Study of ancient magnetism
Paleomagnetism
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 ___________________on average.
• 400 times in last 330 million years.
• Last reversal was 780,000 years ago.
NORMAL REVERSE
200,000 years
Unit 1-Spheres of the Earth
Questions:Is a compass always going to point north?
How does the magnetic field relate to plate tectonics?
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 _________________________
A vertical fault is comprised of a footwall and a hanging wall
vertical or horizontal
Normal Fault
Tension pulls rocks apart causing the hanging wall block to be pulled down.
Normal ______________ mean most common! does not
Reverse Fault
_______________of the normal fault
Compression pushes rocks together and causes the hanging wall to be pushed up
Opposite
Strike-Slip Fault
A strike-slip fault happens when rocks ____________________ each other (shearing)
Moves left or right laterally with very little horizontal movement
slide past
Unit 1-Spheres of the Earth
Questions:What are the three types of faults?
What are the differences in how these faults move?
EARTHQUAKES
Earthquakes Earthquake is the vibration of Earth
caused by a rapid release of energy Often caused by _____________along a break
in Earth’s crust 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
slippage
Causes of Earthquakes 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
San Francisco
Causes of Earthquakes _______________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
Elastic
Aftershocks & foreshocks Aftershocks are ______________earthquakes
produced after a major earthquake Foreshocks are small earthquakes produced
before a major earthquake; can be days or years before quake
smaller
A longitudinal wave and is created by ____________.Demo: push slinky, compressing the coils…
Any individual particle simply ____________________!
Longitudinal Waves
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
compression
moves back & forth
When the disturbance and resulting motion of the medium is _______________to the motion of the wave, it is called a transverse wave and is created by __________.
• Demo: stretch slinky by shaking back and forth
Transverse Waves
•Animation:
•Animation: Transverse Stadium Wave
perpendicular
tension
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 surface first. So, they are called _________ waves (or __-waves). They do the least amount of damage.
Expansions
Compressions Undisturbed Medium
primaryp
Since we know that __________ waves cannot travel through _________, this provides evidence that the earth has a __________ core.
• Transverse waves in the ground are “shear” waves. They travel slower, and are thus, called __________ waves (or __-waves). They do more damage than the p-waves.
It is known that p-waves travel farther than s-waves. Why might that be?
secondary s
transverseliquids
liquid
Using a seismograph, the _________________ from when the p-wave arrives to when the s-wave arrives can be measured. Knowing the ________ of the two waves through the earth, the ________ to the epicenter (starting point) of the earthquake can be determined.
Seismograph
time difference
speeddistance
Locating the Epicenter of an Earthquake
__ different seismographs at __ different locations are required to find the location of the epicenter.
If each seismograph station calculates the distance from itself to the epicenter, then the location of the epicenter is the ___________ of the _________ created.
= seismograph station
epicenter
3 3
intersectionsphere
s
Ring of Fire Earthquake zones
_______of earthquakes occur in narrow zones
Most on outer edge of Pacific called circum-Pacific belt
Second belt Mediterranean-Asian belt
95%
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.
Unit 1-Spheres of the Earth
Questions:What causes Earthquakes?
Where are most Earthquakes located? Why?
TSUNAMIS
Tsunamis Wave caused by ____________ 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
earthquake
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 year1-2
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 means “_______”
fire
What’s inside a volcano? Magma
Chamber- molten rock that feeds a volcano
Vents- cracks in the crust
What is the difference between magma and lava?
How and why do volcanoes erupt?
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.
__________ amounts of gas and a high viscosity (sticky) magma will form an explosive eruption!
__________ amounts of gas and (or) low viscosity (runny) magma will form an effusive eruption
buoyant
Large Small
Explosive Eruptions
Mt. Redoubt
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!!!
Above: Large eruption column and ash cloud from an explosive eruption at Mt Redoubt, Alaska
Pyroclastic flow Lahars/Mud flows Pyroclastic fall Lava flow Noxious Gas Earthquakes
Volcanic Hazards
Courtesy of www.swisseduc.ch
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 ___________________
For example, eruption of Vesuvius, Italy in 79 AD destroyed the city of Pompeii
gas, rock, and ash
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
Vesuvius remains a hazardous volcano with heavily populated flanks: 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!
Bay of Naples
Vesuvius
Naples
Courtesy of www.swisseduc.ch
An eruption of Mt Peleé in 1902 produced a pyroclastic flow that destroyed the city of St. Pierre.
before after
Mt Peleé, Martinique (1902)
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.
Unit 1-Spheres of the Earth
Questions:What causes volcanoes?
Is lava the only thing to worry about with volcanoes?