Starter: 10/9/13 What do you think is occurring at these locations?

Starter What, in your words, is plate tectonics? What is so important about this topic?

NOTES FOR YOUR JOURNAL! Plate Tectonics

Layers of Earth Core – most dense, 2 layers Mantle – 2 layers Crust – least dense

2 Kinds of Crust Continental – less dense Oceanic – more dense

FYI…density of layers (gm/cm 3 ) Inner core 11.5 Outer core 9.0 Mantle 4.5 Oceanic crust 2.9 Continental crust 2.8

Convection Currents Movement of hot liquid or gas  Heated – rises  Cools – drops

Earth’s Crust Cracks… Convection currents in magma (in mantle) cause cracking in crust

Crustal Plates Huge sections of earth’s crust that move relative to each other

Alfred Wegener and Pangaea Pangaea is the name given to the single giant continent in a proposal by Wegener (1912). The theory of continental drift states that the continents were once a single landmass that drifted apart and are still doing so.

Evidence for Continental Drift Wegener tried to support his theory with evidence:  Maps - continents apparently fit together like a jigsaw-puzzle  Plant and animal fossils - coal in Antarctica

Plate Map

Seafloor Spreading Seafloor constantly being created and destroyed New crust at rift valley Crust destroyed at trenches

Evidence for Seafloor Spreading Thin sediment in ridges Age of rock at ridges much younger than continents Patterns of magnetic polarity reversal

Plates Move in 4 Ways Subduction Transform faulting Divergent Convergent

Types of Movement Divergent – plates moving apart (rift valleys in MOR) Convergent – plates coming together Transform – plates slide past each other

Subduction Downward movement of an oceanic plate into the mantle

Subduction Zones Ocean plate into continent Trench, mountains, volcanoes formed

Subduction Plate enters mantle Rock broken Friction heats Magma develops Magma pushed to surface Volcanoes, deep earthquakes

Subduction causes… Seafloor spreading  Magma rises – forms ridges, rises (large!)  Shallow earthquakes

Ocean Trenches Form in subduction zones Deep, narrow, long, steep

Convergent Continents Mountains form

Convergent Boundaries Here crust is destroyed and recycled back into the interior of the Earth as one plate dives under another. These are known as Subduction Zones - mountains and volcanoes are often found where plates converge. There are three different types: oceanic-continental, oceanic-oceanic and continental-continental

Divergent Boundaries At divergent boundaries new crust is created as two or more plates pull away from each other. Oceans are born and grow wider where plates diverge or pull apart. As seen below, when a diverging boundary occurs on land a 'rift', or separation will arise and over time that mass of land will break apart into distinct land masses and the surrounding water will fill the space between them.

Transform Faults When two plates slide horizontally past one another Perpendicular breaks or fracture zones Defined by shallow earthquakes Ex. San Andreas fault in Ca.

CONVERGENT: COLLIDE DIVERGENT: DIVIDE TRANSFORM: SLIIIIDE! WAYS TO REMEMBER THE THREE TYPES OF BOUNDARIES:

Hot Spots Magma chambers in mantle push through surface of crust Crust moves over mantle forming island chain

Continental Collision 2 plates with continents collide Continents don’t sink, subduction doesn’t occur Crust moves up, folds, breaks, etc.

As plates move over hot spots… New islands formed – island chains (archipelagoes)

Old islands sink… Atolls – submerged island group in ring-shape, coral reef grows on top Guyots – extinct submerged volcanoes