Download EARTH (¿)

EARTH ()
Radius:(R)
6.378 x 106 m
3924 miles
(1 R)
Mass:(M)
5.98 x 1024 kg
(1 M)
Mean Density:()
5.5 g/cm3
Unique Features:
LIFE
Structure of the Earth
Deep Wells:
- deepest is 12 km (7.5 miles) in Russia
- temp at bottom = 190oC or 375oF !
Seismology - science of shock waves
- caused by earthquakes, volcanoes, etc.
- shows density and boundary of regions
Two basic types of seismic waves:
Shear (S) waves:
- material displaced side-to-side
- need a solid, will not go through a
liquid
Pressure (P) waves:
- material is compressed
- can travel through any material
RESULTS:
Crust: low density rock (2.5-3.5 g/cm3)
variable thickness (5 – 50 km)
rigid, brittle material
Mantle: high density rock (4.5-10 g/cm3)
2900 km thick
“plastic” - hot, solid but can flow
Outer Core: liquid Iron (some Nickel)
very high density (9-11 g/cm3)
2200 km thick
Inner Core: solid material; (~ 13 g/cm3 )
crystallized iron-nickel ??
Differentiation
- mixing material with different densities
-lower density objects will "float"
-higher density objects will "sink"
- Ice floats on water
- Rocks float on liquid iron
Formation of Earth:
-accretion/collisions of smaller objects
-great amounts of heat released
-original Earth molten
Earth became differentiated:
-densest elements "sink" to center
-iron, nickel
-lightest elements "rise" to surface
-silicon, oxygen compounds
Today, slowly cooling off:
Interior of Earth still very hot
at center (> 5300 oC or 9600 oF !)
Surface of Earth
Crust of Earth is broken into plates:
- 15 major plates move ~ 10 cm/yr
 Plate Tectonics
- Causes many geographic features
- mountain ranges, oceanic trenches
and rifts, island chains
- causes many active features
- volcanoes, earthquakes
http://www.scotese.com/earth.htm
Other processes that affect surface
-Erosion, Deposition (from wind, water)
Mississippi Delta
-Impact Cratering
http://www.passc.net/EarthImpactDatabase/index.html
Tswaing Crater, South Africa
-Life (Human activities)
Earth’s Surface is geologically "young"
- only 10 - 100 million years old