2 Brief Structure of the Earth Divided into layers:Core, mantle, crust
3 Brief Structure of the Earth LithosphereCrust and upper part of the mantleAbout 100 km thickRigidAsthenospherePlastic (gooey) layer beneath the lithosphereMore dense than the lithosphere
4 Brief Structure of the Earth Continental CrustMade up of continents and “edges” of the oceansLightOceanic CrustMade up of ocean floorMore dense than continental crustOlder oceanic crust is more dense than younger oceanic crust
5 Theory of Plate Tectonics Developed in 1960’sCombined continental drift and seafloor spreading.
6 Theory of Plate Tectonics Stated that:The crust and upper mantle (lithosphere) of the earth are broken into sections called plates.These plates sit on top of the plastic (gooey) part of the mantle (asthenosphere).These plates can move apart, converge, or slide past one another through time.
8 Divergent BoundariesWhere plates are moving apart and new crust is forming.Example: Mid-ocean ridges
9 Convergent Boundaries Where two plates collide and crust is destroyed.Subduction zoneArea where a dense oceanic plate sinks under a light continental plate or another less dense oceanic plateForms volcanoes.When two continental plates collide high mountains are formed.
10 Transform Boundary Where one plate is sliding past another plate. The plates may be going in opposite directions or the same direction at different rates.Earthquakes are common
11 Modern Theories for Cause of Plate Tectonics All include convection currents in the mantle.
12 Convection Current Cycle of heating, rising, cooling, sinking Caused by differences in density due to differences in temperatureExample – boiling pan of water
13 Forces Movement of plates result in three types of forces: Tension – pulls rocks apartCompression – pushes rocks togetherShearing – pushes rocks past each other
14 Fault Surface where rock has broken apart and moved. 3 types Normal faultReverse faultTransform (or strike-slip) fault
15 Faults Normal fault Reverse fault Transform fault Rock above the fault moves down.Formed by tension.Reverse faultRock above the fault plane moves up.Formed by compression.Transform faultBodies of rock slide past each other.Formed by shearing.
16 Features of Tension Forces Mid-ocean ridgeWhere oceanic crust is being pulled apart.Rift ValleyWhere continental crust is being pulled apart.
17 Features of Compression Forces MountainsContinental-continental collisionsVery high mountains (folded mountains) are formed.Oceanic-continental collisionsVolcanic mountains are formed.Oceanic-oceanic collisionsIsland arcs (volcanoes that reach above the surface of the ocean) are formed.
18 Features of Shearing Earthquakes Rocks on each side of a strike-slip fault become stuck in one place for a time and then move, releasing energy in the form of an earthquake.
19 Tracking Plate Movement Plate movement is tracked using satellites and lasers.Current rates of movement range from about 1 cm to about 12 cm per year.