Earths Formation and Structure

1
Earths Formation and Structure

2
How Did Earth Form?

• Evidence comes from Earth, other bodies in the
  solar system, and the universe.
• Earth's surface and internal structure and
  composition.
• Rock samples from the Moon.
• Asteroids.
• Planetary probes and rovers.
• Telescope observations.

3
Structure of Our Solar System
Rocky Planets
Gaseous Planets

• Differentiation separation based on mass or
  composition.

4
Structure of Our Solar System
Fig 9.2
Fig 9.2
Outer planets large, mostly gas with solid core
Inner planets small, solid, dense minerals

• Why is the solar system differentiated?

5
Formation of the Solar System

• Contracting dust/gas cloud flattens and begins
  rotating.
• Gravity draws dust into larger bodies.
• Most of the mass is drawn to the center, heats
  up, protosun begins to burn.

Fig 9.3
6
Formation of the Solar System

• Solar wind blows gas/dust away from the protosun.
• Heavier elements condense closer to sun, lighter
  elements further from sun.

Fig 9.3
7
Formation of the Solar System

• Rocky planets dense elements condense at higher
  temperatures closer to sun.

Fig 9.5
8
Formation of the Solar System

• Gas giants lighter elements condense at lower
  temperatures further from the sun.

Fig 9.5
9
Differentiation of Earth

• Earth is divided into layers based on density.
• Solid Layers
• Core (iron-nickel)
• Mantle (pyroxene, olivine)
• Crust (feldspars)
• Liquid/gas Layers
• Hydrosphere (water)
• Atmosphere (gases)

Fig 1.3
10
Differentiation of Earth

• Early Earth was mostly molten ("liquid rock").
• More dense material pulled by gravity to the
  center of Earth.
• Less dense feldspars formed solid crust.

Fig 9.8
11
Origin of Earth's Water

• Earth is unique in the solar system because it
  has lots of water.
• Old hypothesis water from comets late in
  Earth's formation.
• New hypothesis Earth formed "wet" (hydrated
  minerals in meteorites),and water later erupted
  from volcanoes.

12
Origin of Earth's Water

• Evidence
• Isotopic ratio of hydrogen (2H/1H) of Earth's
  water more like meteorites than comets.

Fig 9.14
13
Origin of Earth's Atmosphere

• Was the atmosphere also released from volcanic
  eruptions?

Fig 9.16
Then why are volcanic gases so different than the
atmosphere?
14
Origin of Earth's Atmosphere

• Early atmosphere was probably more like volcanic
  gases.
• Changes due to
• CO2 is stored in limestone, which is made of the
  mineral calcite (CaCO3).
• O2 produced photosynthetic plants (first appeared
  2.3 billion years ago).
• Biology and geology are intimately linked.

15
Origin of Earth's Atmosphere

• Why does nitrogen (N2) make up 77.5 of the
  atmosphere, but only 0.0011 of volcanic gases?
• Hint N2 is not very reactive.

Fig 9.16