Do Now: We all know that wood floats on water. Yet, the wood is not stationary. What drives the movement of the wood on the water?

Aim: How do continents move?

Continental Drift _________ proposed the theory that the crustal plates are moving over the mantle. This was supported by fossil and rock type evidence; also matching of coastline shapes. Wegener

asthenosphere lithosphere mesosphere

Lithosphere (hard) Asthenosphere (soft) Mesosphere

Mantle o C mesosphere Solid ~ 2300 km thick asthenosphere Soft ~3000 km thick lithosphere hard ~100 km thick Inner Core o C mostly iron core inner part is so compressed that it is solid Outer Core o C iron and sulfur liquid Crust floats on top of lithosphere continental crust (granite) 20 to 70 km thick oceanic crust (basalt) ~ 8 km thick Earth formed 4.6 bya

Hess- Convection Cell Theory

Convection Currents The force responsible for plate movement is __________.

Evidence for plate tectonics Pattern of worldwide earthquakes (left) matches plate boundaries (right)

The 3 types of plate boundaries 1. Divergent 2. Convergent 3. Transform

Plate Boundaries The following two slides show maps of the current major plate boundaries and their relative motions. You should be able to describe various landforms created by different plate movements.

Plate Boundaries Divergent Boundary – moving _____ Convergent Boundary – moving ________ Transform Fault Boundary – moving ________________________ apart together sideways past each other

Divergent plate boundaries The Mid- Atlantic Ridge is a divergent plate boundary where sea floor spreading occurs

Divergent plate boundaries Iceland sits atop a divergent plate boundary where continental rifting occurs

Divergent plate boundaries Formation of an ocean basin by rifting and sea floor spreading

Divergent boundary of two continental plates. Creates a __________. Example: _____________ rift valley East African Rift

Convergent plate boundaries Convergent plate boundaries vary depending on the type of crust a. Ocean-continent b. Ocean-ocean c. Continent- continent

Convergent plate boundaries An ocean- continent convergent plate boundary produces the Cascadia subduction zone and Cascade Mountains

Convergent plate boundaries A continent- continent convergent plate boundary produces the Himalaya Mountains

Convergent boundary of two oceanic plates. Creates an ________ and a _____. Example: _____ island arctrenchJapan

Convergent boundary of an oceanic plate and a continental plate. Forms a _______ mountain range and a ______. Examples: _______ or _______ Mts volcanic trench Cascades Andes

Convergent boundary of two continental plates. Forms a ______ mountain range. Examples: ___________, Alps, ______________ folded Himalayas Appalachians

Transform plate boundaries Transform plate boundaries occur between segments of the mid-ocean ridge Can also occur on land (ex: San Andreas Fault)

Transform-fault boundary where the North American and Pacific plates are moving ____ each other. Example: ________________ in California past San Andreas Fault

Plate Boundaries Review Places where plates move apart are called _____________ boundaries. When continental plates diverge a ___________ is formed. When two oceanic plates converge what is created? _________________ The Appalachians formed mainly from continental plate collisions and therefore are a __________ mountain range. The force moving the plates is ____________. Convection currents divergent rift valley an island arc and a trench folded

Inquiry 1.What layer of the mantle do the plates move on? 2.What is the convection cell theory? 3.Wegeners evidence for continental drift includes: ______. 4.Why was his theory disregarded? 5.What did Marie Tharp discover? 6.How are trenches formed?