lecture 23
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Our solar system is made up of?
4 terrestrial planets made of Fe and Si, and 4 large gaseous planets
What are the characteristics of our planets?
All 8 revolve in the same direction, their orbits are in the same ecliptic plane, each planet rotates in the same direction (ex Venus and Uranus), all planets are tilted
Each moon mimics?
The movements of its planet
What are the traits of the inner planets?
small, dense, rocky, and rich in metals
What are the traits of the outer planets?
large and lower density
The spacing between the planets shows a____ . The distance between orbits of planets increased by ___________.
remarkable regularity, a factor of 1.7
What is the oldest planetary material?
The Allende meteorite
What is the Allende meteorite?
Fragment of pre-planetary material. 2 tons of it have been found.
Why is the Allende meteorite important?
it was dated to be 4.567 billion years old by U-Pb radioactive decay method, and it is the best constraint on the age of the Earth and its composition
Early Earth was a _____
homogenous mix of Fe, O, Si, Mg + others. There were no continents, oceans, or atmosphere and was mostly molten
The first form of energy comes from?
Heat
Where did the thermal energy of the condensing early Earth come from?
Collisions of things in our solar system, gravitational compression, and radioactive decay
What happened during differentiation?
Iron and Nickel, heavy metals, sank and formed the core, and the lighter elements moved up and later cooled to form the early crust
What was the result of differentiation?
A density-stratified planet with three main layers: core, mantle, crust
The majority of Earth is made up of?
Iron, then O, then Si
How and when was the moon formed?
Giant impact hypothesis, where the Earth receives a glancing blow from a Mars-size proto-planet during a latter stage of accretion. The debris from the impact forms a disk and reassembles in orbits around Earth to form the Moon, AFTER differentiation, as the Moon is iron-poor
How thick is each layer of Earth
Crust (5-30 km, NYC), Mantle (2900 km from NYC to Denver), Core (6390 Km from the surface, from NYC to Milan)
How do we know Earth’s internal structure?
Determined from studies of how seismic waves behave as they pass through the Earth, where the differences in their travel times correspond to differences in rock properties.
How do seismic waves (primarily P waves) change?
Seismic wave velocity depends on the density and elasticity of rock, seismic waves travel faster in denser rock, and the speed of seismic waves increases with depth (pressure and density increase downward)
What are the characteristics of the crust?
It is rigid, made of light silicate (Si+O (+Na, K, Mg, Al)) minerals to form a silica tetrahedron
What are the differences between continental crust and oceanic crust?
Continental crust is thick (40 km), light, old, and has granite. Oceanic crust is thin (6km), dense, young, and has basalt
What are the characteristics of the mantle?
Made of Dense silicate minerals (rock-forming material), Si+ O (+heavier elements). Rigid but behaves as a viscous fluid
What are the differences between the inner and outer core?
The inner core is solid (Fe is 85% with some Ni), it is 1220 km radius (slightly larger than the Moon). The outer core is liquid-like, molten Fe (85%) with some Ni, convection in liquid outer core generates Earth’s magnetic field
The primordial heat from the condensation phase is?
Still present inside the Earth and being dissipated from the core to the surface, this heat drives all of the geological actions