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4. So, we’re making new crust?
5. Convergent plate boundaries 2 types of crust = 3 possible combinations
Oceanic lithosphere meets oceanic lithosphere
Oceanic lithosphere meets continental lithosphere
Continental lithosphere meets continental lithosphere
6. Convergent boundaries involving oceanic lithosphere At convergent boundaries oceanic plates are subducted.
Subduction is the recycling of oceanic crust into the mantle
7. Play convection animation To view this animation, click “View” and then “Slide Show” on the top navigation bar.To view this animation, click “View” and then “Slide Show” on the top navigation bar.
8. Subduction zones are characterized by two things:
Long chain of volcanoes
10. At oceanic-oceanic convergent boundaries, volcanoes form chains of islands called island arcs.
11. At continental-oceanic convergent boundaries, volcanoes form long mountain chains such as the Cascade Mountains.
12. Subduction zones cause the largest Earthquakes known.
The 2004 Tsunami in the Indian Ocean was caused by an earthquake at a subduction zone.
13. Continent-continent convergent boundaries Neither lithospheric plate can be fully subducted.
Instead, the plates pile up to form huge mountain ranges
16. Play plate motions animation To view this animation, click “View” and then “Slide Show” on the top navigation bar.To view this animation, click “View” and then “Slide Show” on the top navigation bar.
17. Transform plate boundaries Relatively few volcanoes
Lots of earthquakes, though not so large as at subduction zones
25. Begin with rifting—upwelling of hot mantle starts to break the crust apart
26. Faults form rift valleys
Decompression causes melting and volcanism
27. New oceanic crust begins to form. The plate boundary is now a mid-ocean ridge.