The universe is about (~) 15 billion years (B.Y.) old.
Solar system is about 4.5 billion years old
Consists of the sun and 9 planets circling it (figure 9.3)
2 groups of planets:
Terrestrial: small, rocky, dense
Mercury, Venus, Earth, Mars
Jovian: large, gassy, light
Jupiter, Saturn, Uranus, Neptune
Our solar system formed from relatively cold material.
Formed from Nebula of
gas and dust that undergoes accretion
Gravitational attraction- the larger a body
the more dust and gas it pulls in—accretion (figure 1.2).
Most of the material
goes to form the sun, and the left over’s form planets, comets, and meteorites.
The earth warms up very rapidly due to:
Accretion- collisional heating
Compression- inner layers get heated
Decay of radioactive materials inside earth—continues today
The earth becomes (partially) molten.
This is caused (in part) by collision with
mars’ sized body; this created the moon (figure 9.4).
Then started to cool down.
*rocks are very poor conductors of heat*
once “crust” forms on the earth,
inside still remains very hot—even today.
Earth may have been uniform in composition (inside and outside) at first, but
because of heating, it became differentiated- layered (figure 1.5)
Once the temperature (T) inside is high enough, the earth begins to melt, “falls” to
the center, and releases energy and causes more heating.
of iron melt and falls to the center (figure 9.5)
this is called The Iron
This huge heating event causes “boiling off” of volatiles from the inside.
other gasses belched
to the outside
“The Big Burp”
forms the early ocean and
atmosphere (figure 9.6)
Both are very different from what we have today.
We look at layering in 2
Distances measured from surfaces of the earth…?
Earth is based on composition (figure 1.5)
Crust: solid rock (0-~40 km depth)
Mantle: (different type of) solid rock (~40-2900 km depth)
Outer core: liquid iron (2900-5100 km depth)
Inner core: solid iron (5100-6400km depth)
-Based on Mechanical Strength
January 19, 2007
: (0-100 km depth) lithosphere
. Cool, strong, rocky(rigid), rocks much
below melting point. Contains crust and part of the upper mantle
: (100-300 km depth) asthenosphere
. Hot, weak (ductile bends). Rocks
close to their melting point. Consistency of that like tar or silly putty.
Mesosphere: (300-2900 km depth) hot, strong, rigid, rocks under very high
pressure. Not near melting