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
Recent planets were HOT –Compressional Heating –Impact Heating –Radioactive Decay The Earth is layered by Densities –Densest Core –Lightest Crust Formation of Planets
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 Earth’s Layers
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 MY Beginning of well known Geology 600 MY Multicelular complex organisms 700 MY First FISH! 510 MY First Land Plants 430 MY
Dinosaurs evolve Dinosaurs extinct DECEMBER *
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, SiO 2 ) –Thickness: ~5-10 km –Elevation: ~ 3800m below sea level –Age: <200 MY Continental Crust –Density: ~2.75 g/m 3 –Mineral Composition: Granite (Na, K, SiO 2 ) –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
Seismic Studies
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
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 ( km) Deep (>300 km)
250 – 225 MY
Spreading Cycles
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 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
Mid Atlantic Ridge
Mid Atlantic Ridge http
East Pacific Rise
East Pacific Rise
East Pacific Rise
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
San Andreas Fault between Pacific & N. American plates
Plate Tectonics History Alfred Wegener (1915) –Continental Drift Theory –Panagea ( 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