Plate Tectonics Explains: Mountains (Orogeny) Earthquakes Volcanoes Ocean Trenches

Plates Lithosphere is broken into pieces (plates). New lithosphere is constantly: - being made (by volcanoes and ridges) - being lost (by subduction)

Plate Tectonics Magma = liquid rock underground. Lava = liquid rock on surface (becomes igneous rock).

Plate Boundaries (Edges) Where plates meet other plates, three things can happen: Diverge – move apart Converge – come together Transform – move past each other

Divergent Plates When plates move apart: -- youngest rock where plates meet. -- usually under the ocean (mid-ocean ridges), but also on land (rift valleys).

Divergent Plates Convection currents cause upwelling. Move 2.5 cm/yr Mountains, Volcanoes, and Earthquakes

Converging Plates When plates move toward each other. Continental into Continental: -- plates have same density -- crumple and fold, making mountains.

Himalayas

Subduction Oceanic into Continental: -- oceanic crust is denser than continental crust. -- so, it sinks under continental crust into mantle = subduction

Subduction

Thermal Slab

Subduction All subduction zones have: Volcanoes Ocean Trenches Earthquakes Tsunamis

Transform Plates When plates move past each other. -- stress builds up, then releases suddenly, causing an earthquake. -- San Andreas Fault

Hot Spots Some volcanoes form far from plate edges. Hawaiian volcanoes are 4,000 km from a plate boundary. How do they form?

Other Hot Spots Geothermal activity (hot springs, geysers, volcanoes) far from a plate boundary. Yellowstone, Iceland, Galapagos Islands