Astronomy 100 -- Earth as a Planet
EARTH AS A PLANET
= = = = = = = = = = = = = = = =
1) How big is it?
A) Diameter = 1 Earth diameter.
B) Mass = 1 Earth mass.
2) How old it it?
3) Where is it?
1 Astronomical Unit (A.U.) from the Sun.
1 A.U. is defined as the distance from the Earth to the Sun.
8 Light-Minutes from the Sun.
4) What's it doing?
Rotation Period = 24 hours = 1 day.
Revolution Period = 365 days = 1 year.
THE EARTH'S INTERNAL STRUCTURE
Radius about 1/2 Earth radius.
Density of 11 grams/cc.
Mostly nickel and iron.
Center is solid and surrounded by molten layer.
This molten layer probably
produces the Earth's magnetic field.
Outer half of Earth
Composition is volcanic rock
About 15 km in thickness
Lower density rock [also oceans]
Fix Figure 8-15
- - - - - - - - - - - - - - -
This stratified structure implies the Earth has gone
through a process known as
Just after it's formation, the Earth had to be MOLTEN in order
for the high density material to sink to the CORE and the low
density rock to "float" to the surface.
Look at this
Density Profile of the Earth
structure is a
Interior layers are also distinguished by their
A Crustal Plate Map of the Earth
- LITHOSPHERE -- Solid, rigid layer about 100 km thick.
[Crust and thin layer of the mantle]
- AESTHENOSPHERE -- Soft, putty-like layer
(100 km => 350 km).
[Partially melted mantle]
-- Process of crustal disruption
due to the flow of material (aesthenosphere) under the crustal
Fix Figure 8-20
Fix Figure 8-22
The flow of the putty-like aesthenosphere drags the plates in the
lithosphere causing collisions between plates. These collisions
occur in several different ways.
See Fix Figure 8-21. While old plates are
destroyed, new plate material is formed. This process resurfaces
1) Chain of Hawaiian Islands
2) San Andreas Fault. (Plates sliding against each other)
3) Andes Mountains (One plate going under another)
4) The Himalaya Mountain Range. (Two plates pushing upwards)
THE ATMOSPHERE OF THE EARTH
Nitrogen (80%) and Oxygen (20%)
(small amounts of carbon dioxide, water vapor, argon)
When the Earth formed, it possessed its PRIMEVAL
atmosphere (mostly Hydrogen and Helium), which was heated and lost.
The present atmosphere is called the "SECONDARY" atmosphere.
Sources for the secondary atmosphere were:
1) volcanic outgassing
2) comets (source of water)
3) life (separates oxygen from the carbon dioxide)
Solar System Basics.
Our Moon in Detail.
Back to The Front Page.