Terrestrial Planets: Earth

Mercury Venus Earth Moon MarsDistance 1 AU

Orbital Period 1 year

Rotation Period 23.9 hours

Radius (km) 6378 km

Radius (R⊕) 1 R⊕Mass (kg) 6.0x1024 kg

Mass (M⊕) 1 M⊕

Avg. Surface T 59 ̊F

Core: Iron & nickelliquid outer coresolid inner core

Mantle: Mostly Silicate RockSolid (upper mantle) Plastic (lower mantle)

Crust: Silicate Rock & MineralsSolid

Earth: Internal Structure

Trend?

Lithosphere: crust & uppermost mantle

Differentiation•Denser materials in a liquid sink to the center

Gravity!why?

Implications?

• Planets were molten! (and hotter)

Terrestrial Planets: Internal Structure

Core: Mantle: Crust:

Metallic, sometimes moltenSilicates & other rocksSilicates

highest densitymoderate densitylowest density

Back to beginning, Excerpt (15:40-18:30)

Liquid Metal Core + Rotation = Magnetic Field

Planetary Magnetic Fields (B)

Warm planets act as electromagnets!

Current (moving charges) creates magnetic fields

Liquid Metal Core + Rotation = Magnetic Field

Planetary Magnetic Fields (B)

Larger Liquid Metal Core ➝ Stronger Field

Faster Rotation ➝ Stronger Field

Magnetic field protects us from the Solar Wind!!

Preserves our Atmosphere!

Charged particles follow magnetic field lines.

Magnetic Fields on Earth - Create Aurorae!!

Warm Planets...COOL OFF!Heat Escapes by

Convection in mantle

Conduction through lithosphere

Radiation from surface into space

Internal Heat Escaping Causes Geologic Activity!

•Carries heat from interior of mantle (plastic) to base of lithosphere (solid)

Mantle Convection

•Solid Lithosphere Blocks Heat...

...until the Lithosphere cracks!

Mantle Convection

Internal Heat Escaping Causes Geologic Activity: Plate Tectonics

•Surface cracked into ~12 plates•Plates “float” on mantle •Motion causes geological features

Mantle Convection & Plate Tectonics

Tectonics (“building”): Creation of structures within lithosphere

Plate Tectonics: Mountain Building

Ex: Himalayas (Indian➔Eurasian, 1cm/yr)

Convergent Plate Boundary - Plates Collide

Subduction:One plate pulled under another

Ex: East African Rift Zone

Plate Tectonics: Rifts & ValleysDivergent Plate Boundary - Plates Move Apart

Seafloor Spreading: Plates pull apart, lava seeps up and forms new crust

Plate Tectonics: Ocean Ridges/Seafloor Spreading

Ex: Mid Atlantic Ridge

San Andreas Fault (Pacific & North American Plates)

Plates slip sideways few m/second!

Plate Tectonics: Earthquakes & Faults

2/27/10: Chilean Earthquake (Nazca/South American Subduction Zone)

1/12/10: Hatian Earthquake (Carribbean/North American Plates)

Eruption of molten lava onto surface

Hotspot: Place where magma finds a path through the lithosphere

Volcanism (More Geologic Activity!)

Plate motion over hotspots creates Island ChainsVolcanism on Earth

Kauai

Big Island

Shaping Planetary Surfaces - 4 Main Processes

•(Plate) Tectonics•Volcanism

What else?

•Impact Cratering•Erosion

⧽Caused by HEAT!