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24.10.16 earth science: plate tectonics

Migration

La inNiña: progress for

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Why a trench and mountains there?

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What is a subduction zone?

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How does it move? Convection (remember the three heat modes?)

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Where does the heat come from?

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Why is it still hot? (Ussher said 4000 years old)
Uranium!
Where does the Uranium come from?
Two steps: Hydrogen fusion--> Iron (red giants)
Supernova-->all elements beyond Iron, including Uranium

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What makes stars hot? Hydrogen Fusion:
Helium means "from the sun"

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Which ones are formed in first generation stars?

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Anything after that on the periodic table comes from a supernova:

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Uranium is one of these from a supernove, so our planet is being heated from the inside by stuff from a supernova!

So the core is radioactive? Yes.
What makes it hot?
Uranium Fission (different from fusion, this is splitting something heavy)
How do we know what the core looks like?
Nuclear bomb testing: what?
1950's we wanted to know who was testing nuclear weapons, which when tested, make small earthquakes
We (the US) put seismic sensors all over the world to be able to triangulate these tests and determine location and magnitude.
You need to know: there are two types of waves: P waves (fast, compression) and S waves (slow, shear waves)

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Here's what they look like: two types of earthquake waves: P (primary, compression) and S (secondary, shear):

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P waves can travel through solids and liquids (e.g. magma), S waves can only travel through solids
See how they learned about the core?
It is crazier than this: we now know what the inner solid core actually LOOKS like. Wow.

How do we know the plates move?
Started with Navy ships trying to detect submarines by their magnetic field.
What they saw when they crossed the Atlantic:

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What are hotspots then?
Here's the whole picture:

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Have they always moved in the same direction? No:

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How did Wegener's idea get proven? Fossils (https://www.youtube.com/watch?v=jVMLaR4GC-w)

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Super continent was called "Pangea" meaning "all-earth"

Andesitic (sticky magma) volcanoes form where plates go under continents:

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Where are these on the planet?
Look for the red zones, meaning subduction

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Draw these on your globe...

  • Andesitic volcanoes have sticky magma, and can explode when they get stopped up (Vesuvius, Mt. St. Helens, Krakatoa) 
  • Also called strato volcanoes because they are so tall.

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Basaltic Volcanoes have runny magma:

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How does this impact wine? 
Agriculture = soils + water + temp  (temperate biomes anyone?)

As plates move past each other, they create fault lines (cracks)
Three types: slip faults and transform faults (normal or thrusting)

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Transform faults caused the San Andreas quake 

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Thrust faults caused the Bali quake and tsunami: (look this up on youtube)

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Back to earthquakes:
P and S waves:

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P waves are faster than S waves:

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We can use this difference to calculate epicenter (surface location) and hypocenter (actual center):

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AP exam question:
  • How much stronger is a magnitude 7 quake than a magnitude 6?
  • 7 to 5?
  • 7 to 4?

Nuuanu slide: Look up on Wikipedia, how big was the tsunami?

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From our work on biomes, and next our work on plate tectonics, map the following on your globes:

  1. look up where wine is grown on our planet
  2. agriculture is based on what plants need and like: sunlight, temperature, water and soil
  3. wine grows best in soils that are volcanic in origin (Andesitic)
  4. wine also needs temperate zones and enough water
  5. explore where these things intersect
  6. challenge question: If you wanted to grow grapes for wine, knowing that climate change will move all biomes away from the equator, where would you buy land today?

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