Download Plate Tectonics

Formation of Planets
•
Accretion of dust in space due to
GRAVITATIONAL FORCES
– Dust
– Asteroids
– Planets
1. accretion of Heavy elements
2. attraction of Light gases to dense
nucleus
Origin Solar System
Formation of Planets
•
Recent planets were HOT
– Compressional Heating
– Impact Heating
– Radioactive Decay
• The Earth is layered by Densities
– Densest Core
– Lightest Crust
Earth’s Layers
•
Core (Fe, Ni)
–
–
•
Mantle (plastic) –
–
–
•
Inner Core (solid)
Outer Core (liquid)
very close to melting point
Inner Mantle
Asthenosphere
Lithosphere (rigid)
–
–
Upper Mantle (~100km) (Lithosphere)
Crust
•
•
Oceanic
Continental
Earth’s Core, Mantle and Crust
Ocean Floor and Margins
If the entire history of the earth were 1 year long:
•Origin of Earth 4600 MY
•Oceans first form 4000 MY
•Oldest dated rocks 3800 MY
•First life form 3600 MY
•Ocean – Atmosphere equilibrium 1000•Multicelular
MY
complex organisms 700 MY
•Beginning of well known Geology
600 MY
•First FISH!
•First510
LandMY
Plants 430 MY
*
DECEMBER
Dinosaurs
evolve
Dinosaurs
extinct
*
December 31st
• 9:15 pm Homo sapiens evolves
• Historical Times = 1 minute 18 sec.
• Columbus discovers America = 3 sec. till
midnight
• HMS Challenger Expedition = 0.9 sec.
till midnight
• You have been around for ~0.13 seconds
Asthenosphere & Lithosphere
Crust
• Oceanic Crust
–
–
–
–
–
Density: ~2.9 g/m3
Mineral composition: Basalt (Fe, Mg, SiO2)
Thickness: ~5-10 km
Elevation: ~ 3800m below sea level
Age: <200 MY
• Continental Crust
–
–
–
–
–
Density: ~2.75 g/m3
Mineral Composition: Granite (Na, K, SiO2)
Thickness: ~20-90 km
Elevation: ~840m above sea level
Age: <3800 MY
Lithosphere
Study of Earth’s Interior
• Rock Sampling & Drilling
• Meteorites
• Seismic Studies
Rock Drilling
ODP (Ocean Drilling Program)
Meteorites
http://www.nmnh.si.edu/minsci/images/gallery/43.htm
Seismic Studies
http://pangea.stanford.edu/~sklemp/
http://www.oceanmarine.com/
Seismic Studies
• Differential speed of seismic/sound
waves due to density differences
– Pressure Waves (p)
• Parallel to direction of motion
• Travel through liquids
– Shear Waves (s)
• Perpendicular to direction of motion
• DO NOT travel through liquids
Seismic waves refract & reflect at density
boundaries
Seismic Waves
Seismic Waves
Convection Processes
Shallow and deep mantle convection cells
Convection Processes
Divergent Margins - Ridges
• New oceanic crust formation
• Spreading
Convergent Margins - Trenches
• Oceanic crust Destruction
• Convergence & Subduction
Lithosphere Plates
Earthquakes
Shallow (0-70 km)
Medium (70-300 km)
Deep (>300 km)
250 – 225 MY
Spreading Cycles
Hot Spot
Hot Spot
Loihi Volcano
Evolution of
Coral Reefs
Fringe reefs
Barrier reefs
Atolls
Hot Spot Map
Convergent Margins
• Continental Convergent Margins
– Oceanic crust / Continental crust
– Pacific Coast South America
• Oceanic Convergent Margins
– Oceanic crust / Oceanic crust
– Aleutian Trench, Caribbean Arch
• Continental Collision Margins
– Continental crust / Continental crust
– Himalaya mountains
Continental Convergent Margins
Oceanic Convergent Margins
Continental Collision Margins
Continental Convergent Margins
Andes Mountains
Oceanic Convergent Margins
Caribbean Island Arch
Convergent margin vulcanism
St Helens
Convergent margin vulcanism
http://www.rsiphotos.com
http://www.montserratreporter.org/
Soufriere - Montserrat
Continental Collision Margin
Himalaya Mountains
Divergent Margins
• Oceanic Divergent Margins
–
–
–
–
Two spreading plates, upwelling magma
Central Rift Valley and Oceanic Ridge
Mid Atlantic Ridge (Slow 1-5 cm/year)
East Pacific Rise (Fast 9-18 cm/year)
• Continental Divergent Margins
– Crustal upwarp, Rift Valley, Linear Ocean
– East African Ridge, Red Sea
Continental Divergent Margins
African Rift Valley
Mid Atlantic Ridge
http://www.ngdc.noaa.gov/
Mid Atlantic Ridge
http://faculty.washington.edu/lyn4/images/iceland.jpg
Mid Atlantic Ridge
httphttp://www.geomorph.org/gal/mslattery/IAG1.jpg
East Pacific Rise
http://www.ngdc.noaa.gov/
East Pacific Rise
http://geologyindy.byu.edu/
East Pacific Rise
Divergent margin vulcanism
Divergent margin vulcanism
Ocean Crust Age
Convection Processes
Shallow and deep mantle convection cells
Passive Continental Margins
Figure 2.28
Transform Faults
• Two plates slide by each other
• Numerous earthquakes along faults
• Common in divergent and convergent
margins
Transform Fault
Mid Atlantic Ridge
http://www.ngdc.noaa.gov/
San Andreas Fault
between Pacific & N. American plates
•http://quake.wr.usgs.gov/kap/carrizo/
Plate Tectonics History
• Alfred Wegener (1915)
– Continental Drift Theory
– Panagea (200-250 MY)
Plate Tectonics History
• Alfred Hess (1960)
– Seafloor spreading theory
– Geo-Poetry
WHAT DATA PROVES PLATE
TECTONICS?
Figure 2.17
Magnetic Anomaly
Reversal
Earth’s
Magnetic
Polarity
Sediment Thickness
Ocean Sediment Drilling
ODP (Ocean Drilling Program)
Age Difference
Ocean Crust: <200 MY
Continental Crust: <3800 MY
Earth Quake
Distribution
Earthquakes
Shallow (<100km)
Deep (>100km)
Continent Fitting
Paleomagnetism
Direct Movement
Measurements