Formation of Planets Accretion of dust in space

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 (~100 km) (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! • First 510 Land. MY Plants 430 MY *

DECEMBER Dinosaurs evolve Dinosaurs extinct *

December 31 st • 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/m 3 Mineral composition: Basalt (Fe, Mg, Si. O 2) Thickness: ~5 -10 km Elevation: ~ 3800 m below sea level Age: <200 MY • Continental Crust – – – Density: ~2. 75 g/m 3 Mineral Composition: Granite (Na, K, Si. O 2) Thickness: ~20 -90 km Elevation: ~840 m 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/lyn 4/images/iceland. jpg

Mid Atlantic Ridge http: //www. geomorph. org/gal/mslattery/IAG 1. 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 (<100 km) Deep (>100 km)

Continent Fitting

Paleomagnetism

Direct Movement Measurements