Plate Tectonics and Earthquakes
Anomalies
changes on ocean floor
Earthquakes are....
greatest natural threat to humans
How was WWII relevant to plate tectonics?
submarines had sonar sonar inadvertently maps the ocean floor
What season did they decide to work on these things?
summer, better weather and no winter storms
What actually moves are __________/________________ plates.
tectonic/lithospheric
What are the three types of seismic waves?
-primary waves (P) -secondary waves (S) -surface or long waves (L)
What were the 4 other ideas?
-rafting- animals hitched rides across bodies of water -island stepping stones-islands popped up and animals jumped to it -isthmian links-"land bridges" - time of low sea level - ice age -continental drift- very unproven and a cold topic
Depths (how much it occurs)
-shallow (a lot) -intermediate (middle) -deep (not much) ----the deeper you go, the less solid the Earth is
What can earthquakes be caused by?
-slippage long faults - big ones -volcanic erruptions -nuclear explosions
Elastic Rebound
-stresses build up as plates slide past each other -eventually frictional resistance holding the rocks together is overcome ---rocks ruptures, rocks on each plate snap back to their original state
Other explanations included __________________________________.
island hopping, rafting, and land bridges
3. landslides
liquefaction and slumping of saturated layers
When basalt hardens these minerals act like ____________________________.
little bar magnets
Epicenter
location of an earthquake on Earth's surface -directly above the focus
What are the certain minerals that are magnetic?
magnetite (Fe3O4) hematite (Fe2O3)
Certain minerals such as __________&________ are magnetic.
magnetite and hematite
The use of sonar inadvertently ____________________________.
maps the ocean floor
Modern animals like the ___________ were used to prove his theory.
marsoupials
Where does the most damage occur?
most damage occurs within 15-30 miles of the epicenter
Which factors that cause damage can be different because we have human control over them
proximity to humans/buildings design of buildings
What is seafloor spreading?
pushes continents apart
Foreshocks
small earthquakes that precede larger ones
Aftershocks
smaller earthquakes that follow the main earthquake as rocks adjust to new stress fields
Paleomagnetism
study of ancient magnetism in basalts certain minerals are magnetic basalt contains minerals and acquire magnetism when magma hardens
Another name for a place where plates collide is a _____________ zone.
subduction
cynognathus
triassic land reptile
lystosaurus
triassic land reptile
Is intensity similar?
very subjective differs from areas
What is an earthquake?
vibration in the Earth caused by a rapid release of energy
The plates move about as fast as _________________________.
your toenails grow 2-11 cm/year
Earthquake predictions: short-range predictions
(few hours to days) monitoring "precusors" measuring strain in rock, monitoring animal behavior, watching ground water levels
Long-range prediction
(years) statistical estimates of ground motion over time -identify "seismic gaps" - areas that have not had recent quakes -not certain how reliable these methods are
In _________, German meteorologist ___________________ proposed his theory.
1. 1915 2. Alfred Wegener
Mountain ranges like the ________________ here on the East coast and in _________________, _________________________, ______________________ matched.
1. Appalachians 2. England 3. Scotland 4. Ireland
The discovery of the ________________________________ led to the idea of sea-floor ______________.
1. Mid-Atlantic Ridge 2. spreading
Proof
1. The basalt making up the ocean floor gets progressively older moving away from the ridge center. 2. The fossils in the sediment on the ocean floor gets progressively older moving away from the ridge center. 3. The sediment on the ocean floor gets progressively thicker moving away from the ridge center. 4. Given a certain distance from the ridge center in both directions, the basalt making up the ocean floor is the same age. 5. Paleomagnetism
Plate tectonics is the theory that ___________ and _________ move around the earth on large ____________.
1. continents 2. oceans 3. plates
The three boundaries are __________, ___________, and _______________.
1. convergent 2. divergent 3. transform
Three different types of plate boundaries?
1. convergent 2. divergent 3. transform
Convergent boundaries are plates __________ and divergent boundaries are where plates are ___________.
1. destroyed 2. created
Dinosaurs, who are not migratory are found ___________, while migratory groups like _____________ are not.
1. every where 2. mammals
What are two important things at MAR?
1. it lies between the continents, almost equidistant from each shoreline 2. configuration of it mimics coastlines
Factors that cause the damage
1. magnitude of quake 2. duration of vibration 3. stability of substrate upon which buildings occur -loose fill or bedrock 4. proximity to humans/buildings 5. design of buildings
The three types of subduction zones are ________________________, ______________________, __________________________.
1. ocean vs ocean 2. continent vs continent 3. continent vs ocean
Proposed by both ____________ and ______________.
1. scientists 2. nonscientists
What was Wegener's proof?
1. similarity of coastlines 2. mountain ranges on seperate coastlines 3. fossils of similar animals on seperate coasts -dino fossils are found on all continents and mammal fossils aren't 4. paleoclimates 5. modern animals 6. glaciation
What is the damage caused by?
1. the shake of the quake 2. tsunami - seismic sea wave (tidal waves is what it used to be called) 3. landslides 4. fire
Lithospheric Plates
50-75 miles thick, includes crust and upper mantle
What was the public's reaction to Wegener?
50/50 split of how they felt about it couldn't prove how continents moved
In the 19____'s, scientists flocked to this area.
60
Earthquake belts
95% of earthquakes
Who were the two people who talked about seafloor spreading?
Harry Hess - Princeton geologist Robert Dietz - US Coast and Geodetic Survey
Where did the scientists look on the Ridge and why?
Headed to the North Atlantic because that is where the ridge is closest to the surface of the water
Largest magnitude earthquake
Lisbon 1755 (9.5)
Glaciation
Paleozoic glaciation has no pattern with the continents in their present configuration, however, if the continents are placed together then glacial evidence (moraines, striations, drift) all match up
The giant landmass was called __________.
Pangaea
The area around the Pacific Ocean is called the ________________.
Ring of Fire
In the 1960's what occurred?
Scientists flocked to Mid-Atlantic Ridge a deep sea drilling team (Fredrick Vine and Drummond Matthews) headed there to prove sea floor spreading
Modern Animals
The strange evolutionary pattern of the marsupials on Australia indicate that the continent has been isolated from other land masses after a certain point in the evolution of mammals
Mercalli Intensity Scale (1902)
US & Canada -drawbacks = difficult to apply globally -not related solely to earthquake size
The onset of _____________ brought the theory back into the spotlight.
WWII
Magnitude
amount of energy released by seismograms
Divergent
area where plates are forced apart volcanic mountains are produced
Transform
area where plates slide past eachother volcanoes and large earthquakes are common ex. San Andreas Fault
What is Pangaea?
came together and seperated millions of years ago and continents continually moving across the ocean floor
The discovery of __________ on Antarctica was used.
coal
Divergent Plate Boundaries
continental rifts magma rises beneath a continent continent splits apart creates "rift valleys" that are filled with volcanic material and sediments
He could not prove his theory because he __________________________________________.
couldn't prove how they moved (no mechanism)
Intensity
degree of Earth shaking based on amount of damage
Primary (P) waves
fastest waves, compressional (push-pull) motion moves through solids, liquids, and gases
How do earthquakes occur?
focus - the source (location) of an earthquake -energy radiates out from the focus
glossopteris
fossil fern
mesosaurus
freshwater reptile
2. tsunami
generated by submarine landslide or displacement along a submarine fault -more at 300-600 mph -attain heights of 100 ft as they approach land
The ___________ were the main detractors to Wegner.
geophysicists
The sediment on the ocean floor ____________________________________.
gets thicker moving away from the ridge
When is the ocean floor the same age and has the same magnetic orientation?
given a certain distance from ridge center in both directions this occurs
Paleozoic ____________ has no pattern in the world today, but line up the continents and a pattern emerges.
glaciation
Three different types of fossils?
glossopteris, cynognathus, mesosaurus, lystosaurus
Travel-time graphs
graphs of the arrival time of P & S waves that are used to calculate the distance to an earthquake -difference between arrival time of P & S waves is proportional to distance ---need data from at least 3 different seismographs
What was the difference between Wegener vs others?
he actually answered the critics and they kinda shit on him for it because he couldn't explain how the continents shifted
Given a certain distance from ______________________________________.
in both directions, the ocean floor is the same age.
Seismograph
instruments that record seismic waves -contains a free-hanging pendulum -when earth shakes pendulum remains stationary but rest of device shakes
Is there a reliable method of earthquake prediction (short term) ?
no reliable method
Magnitude (2)
objective - a number based on amplitude of largest seismic waves uses logarithmic scaled
Paleoclimates
old climates coal deposits in Antarctica indicate a warm, swampy environment
The basalt on the ocean floor _______________________________.
older as you move away from the ridge
The fossils in the sediment _____________________________.
older as you move away from the ridge
Seismograms
records of seismic activity generated by seismographs P 1st, S 2nd, and L 3rd
The discovery of magnetic __________________ on the ocean floor led to irrefutable proof of moving continents.
reversals/anomalies
4. fire
ruptured gas lines and electric lines -fire-fighting hindered by ruptured water lines and congested roads
What is the Mid-Atlantic Ridge?
series of volcanic mountains 40,000 miles long 1,500 miles wide 2 miles high
Earthquake depth
shallow <45 miles, intermediate = 70-185 miles deep, >185 miles
One of the many elements he used for proof was the ____________ of coastlines.
similarity
Secondary (S) waves
slower, oscillate (shaking motion), moves through solids only
Surface or Long (L) waves
slowest, travels along Earth's surface, does the most damage
Therefore given a certain distance from ______________________________________.
the center of the ridge in both directions, the ocean floor is the same age and magnetic orientation
Seismology
the study of earthquakes started 2,000 years ago in China US after 1906 San Fran quake -vase w/ dragons and marbles to define which direction
The type of boundary in California is a _____________ boundary.
transform