1. End Daily Review #5 What happens at a convergent boundary?
What feature is formed at each type of convergent boundary?
Why is a pyroclastic flow so dangerous?
Would you ever live near an active volcano? Why or why not?
End

2. Divergent Boundaries Plate separate Continental Oceanic
Filled by magma
Volcano
Continental
Rift valley
Oceanic
Mid-ocean ridges
Rift zone = deep cracks between separating plates
Magma fills rift cracks due to lower density it rises up, cools and forms new crust
African rift video: watch section 2

3. Nonexplosive Volcanoes
Common near divergent boundaries
Most common
Produce
Calm lava flows
Huge amounts of lava
Examples
Hawaii
Current eruption
Not divergent boundary
Ocean floor – mid ocean ridge

4. Hot Spots Examples Volcanically active Far from plate boundary
Theories
Mantle plumes
Cracks in crust
Move over time
Due to plate movement

5. Yellowstone Supervolcano video
Yellowstone
Supervolcano video

6. Daily Review #6
How are convergent and divergent boundaries similar? Different?
What causes a hotspot?
Why do hotspots appear to move?
What do you observe about this volcanic eruption? Hypothesize why this volcanic eruption is so different than most?
End

7. Transform Boundary Plates slide past each Not usually smooth
Larger, more frequent earthquakes
Transform boundary: plates are sliding at angles past each other
Not smooth, gets stuck, builds up pressure and eventually releases that pressure in large bursts creating large earthquakes
Images are of the San Andreas Fault – one on the right is of an orchard where the rows shifted due to earthquakes over the years

8. Earthquakes What are they? What is it like? Seismologist Where?
Plate boundary
Rarely in middle of continent
Occur at and create faults
Varying depths
Focus
Epicenter
Ask for student examples of experiences with earthquakes, tell of personal experiences
Seismologists study earthquakes
Most occur at plate boundaries especially transform boundaries
New Madrid fault in middle of North American plate, 1811 earthquake, changed flow of Mississippi, evidence under river of previous faults
Earthquakes occur at or create faults (cracks) of varying lengths and depths
Can occur within 1 km of the surface or deeper than 300km
Focus = where the earthquake originated
Epicenter = surface location of the focus, usually what is referred to in the media because it is a physical location on the map

9. What causes an earthquake?
Plates move
Tension builds
Energy released
Travel as waves
Rocks return to original shape, but different locations
Some rocks exhibit plastic behaviors which is more elastic, when under pressure it just keeps stretching and stays that shape, no earthquakes are formed (photo)
Elastic rebound hypothesis= stretch to breaking point, breaks, releases energy, return to original shape

10. How are earthquakes measured?
Richter scale
Strength (magnitude)
Measuring ground motion
Used by the media
Moment magnitude
More precise
Measures the energy released
Measured at the epicenter
Used by scientists
Richter scale = original scale of measurement for earthquakes, still frequently used in the media, each number is a factor of 10, 2 is 10 times more powerful than 1
An earthquake will have similar richter scale and moment magnitude numbers
Strongest recorded quake = 9.5, Chile 1960, strength of 1 billion tons of TNT

11. Largest Recorded Earthquakes
Recent earthquakes

12. Imaging of Earthquake Waves
Seismograph
Shows local movement
3 main waves
P wave
S wave
Surface waves

13. Earthquake Waves P waves S waves First detected Back-and-forth
Side-to-side
Slower, arrive later
Body waves = deeper below the surface; p and s waves
All waves are created at the same time when the earthquake occurred, but travel at different rates because of how they move and where they are at in the crust
P waves: pressure or primary, arrives first, produces a forward/backward motion, longitudinal wave like a slinky, momentarily deforms the rock
S waves: secondary, moves side to side like an ocean wave, slower and arrive later

14. Surface Aftershocks Foreshocks Rolling Side-to-side Slowest
More destructive
Aftershocks
Foreshocks
Surface waves occur in the upper few km of the surface, 2 types = rolling and side to side (like S wave), slowest so arrives last, most destructive because it is closest to the surface and last the longest
Aftershocks occur after the largest earthquake and there can be many of them and sometimes they are more destructive because structures are already damaged or people are in more dangerous situations
Foreshocks are smaller earthquakes that occur before the major one, used as indicators that a major earthquake is about to occur
Photo: highway overpass in Japan after 2011 earthquake

15. Finding the Epicenter Distance vs. time graph is constant
Closest has smallest time difference
Measure time difference on local seismograph
Compare to graph
Find distance
Repeat for multiple locations
Chinese earthquake detector, 132 ce, bronze urn with 6 dragons’ heads holding bronze ball in mouth, pendulum inside urn, in a tremor pendulum strikes urn causing a ball to fall into mouth of a toad below, creates a large noise, could supposedly tell where earthquake was by which ball fell

16. Finding Epicenter cont.
Use distances found
Draw a circle from each site
Overlap = epicenter

17. Daily Review #7
Which type of boundary do you think has a bigger impact on its surrounding environment? Why?
What is an epicenter and how is it found?
What kind of damage can an earthquake cause and how do you think we could prevent that damage?
If the P wave from an earthquake arrives at 10:45 am and the S wave arrives 10:55 am, how far are you from the epicenter?
End

18. Earthquake Hazard Map
Hazard: how likely a damaging earthquake to occur in an area, determined by past and present earthquake activity

19. Earthquake Prediction
Not exact
Seismic gaps
Area of fewer earthquakes
Likely location of future earthquake
Tension building
Used to predict San Francisco
Also use past frequency
Earthquake prediction is not and probably will never be perfect (able to predict exact size, time and location of an earthquake)
Seismic gaps – areas in an active fault that have relatively few earthquakes
Gap hypothesis : seismic gaps likely to have strong earthquakes in the future
Gap identified in 1988 predicted a 30% chance of at least a 6.5 earthquake in that area; Loma Prieta earthquake occurred in 1989 and measured 6.9
Past frequency and size of earthquakes is also used to predict future earthquakes; example if an area usually has a major earthquake every 100 years, that pattern could possibly continue and if the last major earthquake was 100 years ago then one is likely to happen in that area (if the pattern continues)

20. Destruction from Earthquakes
Liquefaction
Mixing soil with underground water
Sinkholes
Landslides
Fire
Broken gas and electrical lines
Lack water to fight
Building and highway damage
Liquefaction is created when the shaking of an earthquake causes groundwater and soil to mix liquefying the soil which creates sinkholes because “liquid” soil takes up less space and shrinks down
Landslides occur as unstable ground is shaken loose
Fire from broken gas and electrical lines is made worse by the lack of water to fight the fires caused by broken water lines
Building and highway damage caused by the shaking

21. Tsunami Closer to shore Slows Increases in height Causes Massive waves
Underwater earthquake - ocean floor movement
Landslides
Volcanic eruptions
Massive waves
Closer to shore
Slows
Increases in height
Tsunami means harbor wave
Can travel as fast as 600 mph which is as fast as a jet plane, generally traveling at around 35mph when it hits land
Largest ever recorded was 1700 ft high in 1958 in Alaska and only 2 people died
80% occur in the Ring of Fire
The backwash from the tsunami is sometimes more dangerous and powerful pulling people and items out into the ocean
Looks like a wall of water, does not break or curl like regular ocean waves

22. Tsunami warning system Only a few a year Most recent (major)
Indonesia (Dec )
Japan (Mar. 2011)
Seiche
Tsunami warning system: series of buoys out in the Pacific Ocean (where most tsunamis occur), monitor ocean height especially after a major earthquake somewhere
Japan 2011: created a wave 131ft. high in some areas, killed over 15,000 people (some not directly from the wave), will cost $232 billion to rebuild and repair all the damage
Seiche is a tsnumai that occurs in a lake, similar to when you get into a bathtub and water sloshes around, this occurred at Quake Lake
Indonesia: killed over 200,000 people in 14 countries, earthquake was 9.0 located entirely under the ocean, land moved over 30 feet because of this quake

23. Daily Review #8 How are earthquakes created?
How are P, S and surface waves similar? Different?
What is a tsunami and how is it made?
Look at the Ring of Fire on the map below. Why is it unique and what is causing it to have those features?