Upload
kerry-reynolds
View
213
Download
0
Tags:
Embed Size (px)
Citation preview
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