The Earth Classify stuff –Composition: Crust, mantle, outer core, inner core –Physical Properties Atmosphere, biosphere, lithosphere, asthenosphere, mesosphere, outer core, inner core

Layers

Layers - How do we know? Earthquake evidence –Primary waves of earthquakes (P-waves) Compression and expansion Deflects in compositional changes (solid/liquid) –Secondary waves (S-waves) Up and down oscillation Not transmitted in liquid –So…

The Theory: Plate Tectonics The main features of plate tectonics are: –The Earth's surface is covered by a series of crustal plates. –The ocean floors are continually, moving, spreading from the center, sinking at the edges, and being regenerated. –Convection currents (the driving force) beneath the plates move the crustal plates in different directions. –The source of heat driving the convection currents is radioactivity deep in the Earths mantle.

The Evidence Fit of continents Fossil evidence Paleoclimate data Ring of fire – –Earthquakes and volcanoes Seafloor spread Age of seafloor rocks Magnetic anomalies

Plates Defined by: Earthquakes Volcanoes Ridges Trenches

The Force: Convection Currents Convection Currents: Rise from mantle below mid ocean ridges Spread out (and form new rock in the split) Cool as they move farther from the ridge Eventually arrive at subduction zone Crust heats as it sinks – can eventually melt Friction causes earthquakes Density differences cause volcanoes Explains why plate boundaries are defined by –Earthquakes –Volcanoes –Ridges –Trenches

Types of Volcanoes Oceanic crust only –Mainly gentle, lava is basaltic (dark, mafic rocks) –Shield Volcanoes Gentle slopes, flat Ocean and continental crust –Composite or Strato volcanoes Types of volcanoes: Types of volcanoes: h ttp://volcano.und.nodak.edu/vwdocs/vwlessons/volcano_types/index.html