Introduction to the Solar System

Earth tilted 23.5 degrees with respect to orbit around the sun -- Seasons
View from the side (board)
Moon in orbit around the Earth--tilted 5 degrees with respect to equator
Moon phases (interactive animation) -- View from the top (board)
Sidereal day (interactive animation) -- Earth rotates once with respect to the stars
Precession -- wobbling of top

Outer planets go through a loop in the sky
This is due to the fact that the Earth goes faster in its orbit
Like a faster runner on an inside track -- catch up and pass slower outer runners. The outer runners appear to slow down and go backwards for a while

They are all spheres
They all revolve around the sun
What are these spheres? -- They all started out as molten bits of material left over from the origin of the solar system
Further in, close to the forming sun where it was hot, the molten blobs were made of Fe and metal, with some rocks mixed in.
A little further out -- molten blobs were rock, some metal, some ice
Even further away still, rock and ice, and frozen gases
ice: water, CO2
frozen gases: CH4, N2, NH3

Heavy stuff sinks to the center
Light stuff floats to the surface of the blob
Medium stuff floats in between
Core: Fe, Ni
Mantle: Heavy rocks, but lighte than metal
Crust: Hardened scum that floats on the surface, light rocks
This is called differentiation
There is something else really special, a tincture of tenderness--
water, ice, atmosphere -- nurtured life
Some of it came with the light rock and was squeezed out onto the surface
Some of it came at the enf of Earth's formation by the bombardment of comets--a time when lots of left over pieces from the solar system formation were flying around
Comets: Water, nitrogen, and organic compounds

The core is half the diameter of the Earth
Solid inner core
Liquid outer core
How do we know?
Earthquakes -- they make all kinds of waves that go right through the Earth
Some kinds of waves can't go through liquids
To observers on the other side of the planet, these waves don't get through, but the others do
Friction of Fe and Ni falling down through the blob heated up the Earth-- melted it even more, making it even easier still for the core to form

Heavy, hot rocks
Mobile --rocks participate in convection to get the heat out (cooler at top than in center)
Very slowly, convection turn in 100's of My
3000 km deep

2 kinds:
Oceanic crust -- dense, 5 km thick made of basalt
Continental crust -- lighter, granite, some basalt, 30 km thick
The continental crust is lighter, and floats higher
The oceans aren't just shaped the way they are because of sea level. The crust that pushes its way up and floats above everything else is the continents

Crust-Mantle-Core: Compositional differences
Lithosphere-aesthenosphere-mantle-core: separation due to rigidity
Lithosphere--solid, 'rock shell'
aesthenosphere -- partly melted, 'weak shell'

Mantle is convecting and cooling
It tries to drag the lithosphere with it in spots
Solid shell cracks into plates -- 13 on Earth
Cracks--sites of volcanoes and earthquakes -- Faults
Plates try to convect as the lids on the mantle convection cells
Ridges -- where upwelling melted rock comes up in a crack. Pushes plates away from each other
Subduction zone--where one plate slides under another
Movement of continesnts cm/yre
Pangea, Gondwanaland -- supercontinents of the past
Broke apart and reformes every 300 My
Earth is 4.5 By old, 15 times longer than this
Because of this, there is no ocean floor over 300 My old
Subduction zones--plate slides under, heats rocks, forms volcanoes
Ring of Fire -- explosive volcanoes, steep sides, ash
Ocean plates usually go under continental plate, because they are denser
Marianis trench from Japan to Phillipines
But sometimes continents bump into each other and you get partial subduction-- Himalayas
One other kind of volcano --hot plume rising from either the mantle or core-mantle boundary
They hit the bottom of the lithosphere and spread out
Where the magma makes it to the surface, we have hot spot volcanism, like Hawaii (the biggest spot) magma--lava. Shield volcanoes broad and not steep

Water and CO2squeezed and boiled out of rocks during Earth's formation
Also, CO2 and N2 from comets.
So hot that it all went into the atmosphere
As the Earth cooled, water condensed into oceans, leaving a thick CO2 atmosphere
CO2 dissolved into the oceans like a vast reservoir of seltzer
CO2 in ocean water reacted with bottom rocks to form carbonates
CO2 atmosphere became thinner
plants began photosynthesis, lowered CO2 levels

76% N2
22% O2
almost 1% H20
almost 1% argon
trace amounts of everything else, including CO2
Wind
Air is transparent to sun--Sun heats the ground
Ground heats the air
Air rises, convection, wind
As moist air rises and gets cool, it can't hold as much water. Water condenses out as clouds, which eventually rain
But clouds mostly reflect light back into space without absorbing it
Heat at equator -- rises, falls back near the poles -- Hadley circulation
Spinning Earth -- Coriolis force
As wind goes N, it is forced West
If this gets out of hand, we have a hurricane

VIDEO: BLUE PLANET

6/5/96