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- 1000oCmesosphere

•Solid•~ 2300 km thick

asthenosphere• Soft•~3000 km thick

lithosphere•hard •~100 km thick

Inner Core- 4300oC

• mostly iron core

• inner part is so compressed that it is solid

Outer Core- 3700oC

• iron and sulfur

• liquid

Crust• floats on top of lithospherecontinental crust (granite)

•20 to 70 km thick oceanic crust (basalt)

• ~ 8 km thick

Earth formed 4.6 bya

Hess- Convection Cell TheoryHess- 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 arc trench Japan

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

volcanictrench Cascades Andes

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

folded HimalayasAppalachians

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?