platetectonics theory.ppt
- 2. Explain the Plate Tectonic theory. Describe the distribution of active volcanoes, Earthquake epicenters, and major mountain belts.
- 3. 1. What is the theory of plate tectonics? 2. What are the three types of plate boundaries?
- 4. • The Earth’s crust and upper mantle(Lithosphere) are broken into sections called plates • Plates move around on top of the mantle like rafts • A section of the lithosphere that slowly moves over the asthenosphere, carrying pieces of continental and oceanic crust.
- 5. The theory which states that pieces of Earth’s lithosphere are in constant motion, driven by convection currents in the mantle. • Plates move slowly in different directions Cause different geologic events (like earthquake, volcano, etc.)
- 7. Convection Currents in the mantle move the plates as the core heats the slowly-flowing asthenosphere (the elastic/plastic-like part of the mantle).
- 9. The edges of Earth’s plates meet at plate boundaries. Extended deep into the lithosphere
- 10. Divergent Boundaries Convergent Boundaries Transform Boundaries
- 11. A plate boundary where two plates move away from each other. RIFTING causes SEAFLOOR SPREADING
- 14. • A geologic feature or event… May form RIFT VALLEYS on continents SEA-FLOOR SPREADING in the ocean
- 15. • Divergent is like “dissecting” or “dividing” • If you pull warm bubble gum or silly putty, it will thin in the middle until it is stressed so much that it breaks. • Happens on land & under H2O
- 16. • Mid-ocean ridges • rift valleys • fissure volcanoes
- 17. A plate boundary where two plates move towards each other. Boundaries between two plates that are colliding This stress is called COMPRESSION
- 18. Places where plates crash (or crunch) together or subduct (one sinks under)
- 19. Ocean plate colliding with a less dense continental plate Subduction Zone: The process by which oceanic crust sinks beneath a deep-ocean trench and back into the mantle at a convergent plate boundary.
- 21. What else happens at Convergent Boundaries? VOLCANOES occur at subduction zones
- 23. • Ocean plate colliding with another ocean plate • The less dense plate slides under the more dense plate creating a subduction zone called a TRENCH
- 25. A continental plate colliding with another continental plate Have Collision Zones: A place where folded and thrust faulted mountains form.
- 26. • May form Mountain Ranges. These are Folded Mountains, like the Himalayas or the Rockies.
- 27. A REVERSE FAULT Rock is forced upward as it is squeezed.
- 28. • Convergent = “Connecting” boundaries • May work like a trash compactor smashing rock. – Rock goes crunches up to make folded mountains. – Rock goes down “under” @ subduction zone.
- 29. A plate boundary where two plates move past each other in opposite direction.
- 30. Rock is pushed in two opposite directions (or sideways, but no rock is lost) This stress is called SHEARING
- 31. • May cause Earthquakes when the rock snaps from the pressure. • A famous fault @ a Transform Boundary is the San Andreas Fault in California.
- 33. A STRIKE-SLIP FAULT Rocks on each side of the fault slip past each other as they break.
- 34. Shearing means cutting (“Shears” are like scissors) Transform boundaries run like trains going past each other in different directions & they shake the ground!
- 35. Can you match the boundary name correctly with its diagram? A._____________ B._____________ C._____________