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Earth
[History | Information
| Data]
The Earth formed in the inner solar nebula.
it passed through the four stages of planetary development that other solid planets also
experience to varying degrees. The four stages are as follows:
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| 1. |
Differentiation: The earth was originally molten, and at
this time the matter separated according to density. Heavier substances (iron) sank to the
core, while lighter substances floated to the surface. This formed the crust. |
| 2. |
Cratering: The solid surface is bombarded with clutter
from the solar system. The moon is still in this phase. |
| 3. |
Flooding: Decay of radioactive elements heats the planets
interior, causing lava to well up through fissures and flood deeper basins. When the
planet cooled, water fell as rain and flooded the basins to form the oceans. |
| 4. |
Surface Evolution: Plate tectonics and erosion change the
surface features slowly. The Earth's current phase. |
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The Earth is made up of several different layers, each composed of different elements.
This term is called differentiation. The density of the Earth is 5.52g/cm3, and
the crust is much less dense so it "floats." The four layers of the Earth are:
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| 1. |
The crust is very thin relative to the radius of the
Earth, only 35-60km thick. The crust of the earth is proportionally thinner than the skin
of an apple. In some thin places, such as Yellowstone National Park in the USA, the
underground can reach extreme temperatures very close to the surface. They average 400-460oF
only one mile down. In some places, at that depth, the temperatures are high enough to
melt glass. |
| 2. |
The mantle is a layer of dense rock which is extremely
hot and under tremendous pressure. Due to these factors, the rock becomes malleable. As
the mantle moves, the crust floating above it moves also, causing earthquakes. |
| 3. |
The liquid core is made of molten iron and nickel and has
a density of about 14g/cm3 (crust: 3.0g/cm3; mantle: 4.4g/cm3). |
| 4. |
The solid core is the same as the liquid core, except the
molten iron and nickel are under so much pressure, they return to their solid state. |
Atmosphere:
The current atmosphere of the earth is called the secondary atmosphere. The primary
atmosphere was created soon after the earth was created. It was rich in carbon dioxide,
nitrogen, and water vapor. When the volcanoes erupted, they released large amounts of
gasses. The carbon dioxide dissolved into the oceans leaving nitrogen behind (70% of
"air"). The oxygen components were contributed by green plants.
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Distance from Sun:
Mean— 92,960,000 mi.
Shortest— 91,400,000 mi.
Greatest— 94,500,000 mi.
Closest approach to Earth— ----------
Length of year (earth-days)— 365.22
Average orbital speed— 18.51 mi. per sec.
Diameter at equator— 7,926
Rotation period— 23 hrs. 56 min.
Tilt of axis "(degrees)— 23.44
Temperature— -128.6 to 136 *F
Atmosphere:
Pressure— 14.7 lbs. per sq. in
Gasses— Nitrogen, oxygen, carbon dioxide, water vapor
Mass (Earth=1)— 1
Density (g/cubic cm)— 5.52
Gravity (Earth=1)— 1
Number of known satellites— 1 |
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[Mercury | Venus | Earth
| Mars | Jupiter]
[Saturn | Uranus | Neptune | Pluto]
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