Starter: 10/9/13

What do you think is occurring at these locations?

Starter 10-8-13

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 layersCrust – least dense

2 Kinds of Crust

Continental – less dense

Oceanic – more dense

FYI…density of layers (gm/cm3)

Inner core 11.5 Outer core 9.0Mantle 4.5Oceanic crust 2.9Continental crust 2.8

Convection Currents

Movement of hot liquid or gas Heated – risesCools – 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 Pangaea11 - 11

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 Drift11 - 12

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 Spreading11 - 14

Seafloor constantly being created and destroyed

New crust at rift valleyCrust destroyed at trenches

Evidence for Seafloor Spreading11 - 15

Thin sediment in ridgesAge of rock at ridges much younger than

continentsPatterns of magnetic polarity reversal

Plates Move in 4 Ways

Subduction Transform faultingDivergentConvergent

Types of Movement11 - 17

Divergent – plates moving apart (rift valleys in MOR)

Convergent – plates coming togetherTransform – plates slide past each other

Subduction

Downward movemen

t of an oceanic

plate into the

mantle

Subduction Zones11 - 19

Ocean plate into continentTrench, mountains, volcanoes formed

SubductionPlate enters mantleRock brokenFriction heatsMagma developsMagma pushed to surfaceVolcanoes, deep earthquakes

Subduction causes…

Seafloor spreadingMagma rises – forms ridges, rises (large!)

Shallow earthquakes

Ocean Trenches

Form in subduction zones

Deep, narrow, long, steep

Convergent Continents11 - 23

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 zonesDefined by shallow earthquakesEx. San Andreas fault in Ca.

CONVERGENT: COLLIDEDIVERGENT: DIVIDE

TRANSFORM: SLIIIIDE!

WAYS TO REMEMBER THE THREE TYPES OF

BOUNDARIES:

Hot Spots11 - 28

Magma chambers in mantle push through surface of crust

Crust moves over mantle forming island chain

Continental Collision

2 plates with continents collideContinents 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