Formation of Planets

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Formation of Planets

• Accretion of dust in space due to GRAVITATIONAL
  FORCES
• Dust
• Asteroids
• Planets
• accretion of Heavy elements
• attraction of Light gases to dense nucleus

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Origin Solar System
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Formation of Planets

• Recent planets were HOT
• Compressional Heating
• Impact Heating
• Radioactive Decay
• The Earth is layered by Densities
• Densest Core
• Lightest Crust

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Earths Layers

• Core (Fe, Ni)
• Inner Core (solid)
• Outer Core (liquid)
• Mantle (plastic) very close to melting point
• Inner Mantle
• Asthenosphere
• Lithosphere (rigid)
• Upper Mantle (100km) (Lithosphere)
• Crust
• Oceanic
• Continental

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Earths Core, Mantle and Crust
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Ocean Floor and Margins
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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 MY

• Multicelular complex organisms 700 MY

• Beginning of well known Geology
• 600 MY

• First FISH!
• 510 MY

• First Land Plants 430 MY

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DECEMBER
Dinosaurs evolve
Dinosaurs extinct

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December 31st

• 915 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

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Asthenosphere Lithosphere
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Crust

• Oceanic Crust
• Density 2.9 g/m3
• Mineral composition Basalt (Fe, Mg, SiO2)
• Thickness 5-10 km
• Elevation 3800m below sea level
• Age lt200 MY
• Continental Crust
• Density 2.75 g/m3
• Mineral Composition Granite (Na, K, SiO2)
• Thickness 20-90 km
• Elevation 840m above sea level
• Age lt3800 MY

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Lithosphere
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Study of Earths Interior

• Rock Sampling Drilling
• Meteorites
• Seismic Studies

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Rock Drilling
ODP (Ocean Drilling Program)
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Meteorites
http//www.nmnh.si.edu/minsci/images/gallery/43.ht
m
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Seismic Studies
http//pangea.stanford.edu/sklemp/
http//www.oceanmarine.com/
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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

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Seismic Waves
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Seismic Waves
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Convection Processes
Shallow and deep mantle convection cells
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Convection Processes
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Divergent Margins - Ridges

• New oceanic crust formation
• Spreading

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Convergent Margins - Trenches

• Oceanic crust Destruction
• Convergence Subduction

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Lithosphere Plates
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Earthquakes
Shallow (0-70 km) Medium (70-300 km) Deep
(gt300 km)
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250 225 MY
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Spreading Cycles
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Hot Spot
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Hot Spot
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Loihi Volcano
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Evolution of Coral Reefs
Fringe reefs
Barrier reefs
Atolls
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Hot Spot Map
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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

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Continental Convergent Margins
Oceanic Convergent Margins
Continental Collision Margins
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Continental Convergent Margins
Andes Mountains
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Oceanic Convergent Margins
Caribbean Island Arch
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Convergent margin vulcanism
St Helens
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Convergent margin vulcanism
http//www.rsiphotos.com
http//www.montserratreporter.org/
Soufriere - Montserrat
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Continental Collision Margin
Himalaya Mountains
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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

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Continental Divergent Margins
African Rift Valley
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Mid Atlantic Ridge
http//www.ngdc.noaa.gov/
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Mid Atlantic Ridge
http//faculty.washington.edu/lyn4/images/iceland.
jpg
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Mid Atlantic Ridge
httphttp//www.geomorph.org/gal/mslattery/IAG1.jpg
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East Pacific Rise
http//www.ngdc.noaa.gov/
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East Pacific Rise
http//geologyindy.byu.edu/
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East Pacific Rise
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Divergent margin vulcanism
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Divergent margin vulcanism
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Ocean Crust Age
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Convection Processes
Shallow and deep mantle convection cells
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Passive Continental Margins
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Figure 2.28
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Transform Faults

• Two plates slide by each other
• Numerous earthquakes along faults
• Common in divergent and convergent margins

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Transform Fault
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Mid Atlantic Ridge
http//www.ngdc.noaa.gov/
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San Andreas Faultbetween Pacific N. American
plates

• http//quake.wr.usgs.gov/kap/carrizo/

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Plate Tectonics History

• Alfred Wegener (1915)
• Continental Drift Theory
• Panagea (200-250 MY)

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Plate Tectonics History

• Alfred Hess (1960)
• Seafloor spreading theory
• Geo-Poetry
• WHAT DATA PROVES PLATE TECTONICS?

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Figure 2.17
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Magnetic Anomaly
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Reversal Earths Magnetic Polarity
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Sediment Thickness
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Ocean Sediment Drilling
ODP (Ocean Drilling Program)
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Age Difference Ocean Crust lt200 MY Continental
Crust lt3800 MY
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Earth Quake Distribution
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Earthquakes
Shallow (lt100km)
Deep (gt100km)
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Continent Fitting
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Paleomagnetism
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Direct Movement Measurements