Plate Tectonics Subduction Topic Subduction Essential Question How
Plate Tectonics • Subduction
Topic: Subduction Essential Question: ¨ How do plates sink into the Earth?
Lithosphere (crust + upper mantle) Continental lithosphere -thick, keeps heat in -always low density -brittle, but more squishy Ocean lithosphere -thin, not as good at keeping heat in -dense when cold and old -even denser than asthenosphere when old
Plate Tectonics definition l l l Plate Tectonics– say it 3 times! Definition: The theory that the earth’s outer layer is broken into solid plates that interact with each other Simply: earth’s surface moves around What is technology? Tectonic=Greek for building/making
The Plates: Brittle land mass that moves as a unit
World's Earthquakes
World's Volcanos
Types of Plate Motion l Toward l Away l Side to side
Types of Plate Motion l Toward. CONVERGENT l Away l Side to side
Convergent Boundary l l l Convergent – say it 3 times! Definition: Place where two or more lithospheric plates move toward one another Simply: plates come together Have you and your friends ever converged somewhere? Con=with; verge=bend, convergent=bend with or bend together
Continent vs. Ocean l Predict what will happen!
Did you predict this?
Continent vs. Ocean
The result of ocean-continent convergent boundaries: Subduction Continental plate stays up Ocean plate goes down
Subduction: One plate goes under another Why does trench form? Why does water leave the subducting plate? Why does magma go up to the surface? Why is this plate boundary also called “destructive”? Biggest Earthquakes (and Tsunamis)
Trench: Deep place where ocean plate dives down Deepest places on Earth!
Arc: 'curved' chain of volcanos Subduction causes volcanos to form in a line (or arc). Magma is formed as water is released from the ocean plate under heat & pressure and rises to surface
Why arcs? Paper-covered ball demo
How do we know? Earthquake trends Earthquakes get deeper and. . . Follow the plate down!
Where?
Ocean vs. Ocean l Predict what will happen!
Did you predict this? Evenly matched, but older one almost always will lose. . .
Ocean-Ocean subduction The older, colder, and therefore denser ocean plate loses the battle, and that plate subducts. The younger, warmer, and less dense ocean plate stays on top.
Similar features in ocean-ocean subduction -Trench -Very large earthquakes -magma rising, making islands instead of mountains -Arc (called Island Arc)
Where? Japan
Mini Quiz 1. 2. 3. 4. 5. What is a plate? What type of motion is convergent? What type of plate subducts? Why do plates subduct? What does subduction cause?
Mini Quiz 1. What is a plate? – Piece of lithosphere that moves as a unit 2. What type of motion is convergent? – Towards, together 3. What type of plate subducts? – Ocean, denser 4. Why do plates subduct? – Density 5. What does subduction cause? – Volcanic arc, trench, giant earthquakes, tsunamis
- Slides: 27