Lecture 6: Earth as a Planet

1. The Young Earth2. Earth as a planet: interior3. Plate tectonics4. Atmosphere

News from Mars:

Opportunity Mars Rover at Santa Maria Crater - Feb. 2011

News from Mars:

The Formation of the Earth

• Precise timeline of early events.

The Planets

Earth as a planet - interior

Earth interior - seismic waves

Earth interior - seismic surface waves

Earth as a planet - plate tectonics

Plate tectonics

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Earth as a planet - plate tectonics

Earth as a planet - plate tectonics

Earth - plate collision & subduction

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Evidence from seismictomography for thesubduction of the plateunder Japan.

Variations in shear-wavevelocity, vS

Earth as a planet - plate tectonics

Earth as a planet - plate tectonics

Earth as a planet - tectonics

The Terrestrial Planets

Mercury Venus Earth Mars

Mars as a planet - interior

Earth

Mars as a planet - NO plate tectonics

Wyatt et al. [2004]; Data from Mars Odyssey THEMIS

basalt

dust

“altered basalt” (smectite, palagonite, zeolites)

Surface composition from thermal emission spectra

Mars as a planet - the surface

Earth as a planet - atmosphere

Main points to take home:

1) Hadean Earth (4 430 - 4 000 Myr): heavy bombardment epoch, outgassing, oceans

2) Earthquakes & seismic waves - interior map3) Earth’s interior is differentiated - iron core4) Plate tectonics - Earth’s crust is broken into

plates; mantle convective currents cause these plates to move

5) Atmosphere - Earth had 3 types of atmospheres, in terms of composition; today’s is mostly N2 (78%) and O2 (21%).