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ASTA01H3 (13)
Chapter

Chapter Seven Review: Earth

10 Pages
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Department
Astronomy
Course Code
ASTA01H3
Professor
Brian Wilson

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October 12th, 2010
ASTA01H
Intro to Astronomy and Astro Part I
Chapter Seven: Earth
Overall Structure of Planet Earth
Earths mass is 6.0kg
Earths radius is about 6400km
oDividing these together, we find that Earths average density is 5500
kg/
We can conclude that because the surface layers have densities much less
than average, much denser material must lie deeper
Earths interior
oA thick mantle surrounds a smaller, two-part core
oA relatively thin crust, compromising the solid continents and sea floor
oThe hydrosphere, contains the liquid oceans
oAn atmosphere of air just above the surface
oAt much greater altitudes, a zone of charged particles trapped by Earths
magnetic field forms the magnetosphere
Earths Atmosphere
Mixture of gases:
oNitrogen 78%
oOxygen 21%
oArgon 0.9%
oCarbon Dioxide 0.03%
oWater vapour varies from 0.1 to 3%
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Atmospheric Structure
Troposphere: The portion of the atmosphere below about 12km (weather zone)
Stratosphere: Above the troposphere to an altitude of 40 to 50km
Mesosphere: 50 to 80km from Earths surface
Ionosphere: Above about 80km. Where the atmosphere is kept partially ionized by
solar ultraviolet radiation
Atmospheric densities decrease steadily with increasing altitude
The troposphere is the region of Earths (or any other planets) atmosphere
where convection occurs
Convection: The constant rising of warm air from the Earths surface and the
concurrent downward flow of cold air to replace it
At higher altitudes the opposite effect occurs: The air gradually cools,
becoming more denser and therefore sinking back to the ground
These convection cells are responsible for atmospheric heating, as well as surface
winds
Above about 100km, in the ionosphere, the atmosphere is greatly ionized
from the Suns radiation spectrum, which breaks molecules into atoms and
atoms into ions
oThe degree of ionization increases with altitude
Atmospheric Ozone
Ozone Layer: At an altitude of around 25km, incoming solar ultraviolet radiation is
absorbed by atmospheric ozone and nitrogen (Ozone = )
oThis solar radiation breaks ozone down, forming oxygen gas again
Ozone is one of many insulating spheres that protect our planet
Surface Heating
The Earths surface absorbs much of the solar radiation that is not deflected
by the Earths atmosphere
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Eventually the Earth reradiates as much energy back into space as it receives
from the Sun, this stable balance, if uninterrupted, would put Earths average
temperature at -23
Solar radiation, which includes a full spectrum of various forms, arrives at the
Earth as sunlight, however some of these radiations forms are blocked or
absorbed by the Earths atmosphere
This reemitted energy is in the form of infrared (heat) radiation, which is
partially blocked by Earths atmosphere, allowing for a warmer average
temperature as some of the heat is retained within the atmosphere
This partial trapping of solar radiation is known as the greenhouse effect
The magnitude of the greenhouse effect is highly sensitive to the
concentration of greenhouse gases (gases that absorb infrared radiation) in the
atmosphere
oCarbon dioxide and water vapour are the most important of these
Origins of Earths Atmosphere
When Earth first formed, any primary atmosphere it might have had would have
consisted of the gases most common in the early solar system:
oHydrogen
oHelium
oMethane
oAmmonia
oWater Vapour
Almost all of this low-density material (especially hydrogen and helium)
escaped into space
Consequently, Earth developed a secondary atmosphere, which consisted of gases
outgassed (expelled) from the planets interior from volcanic activity, which include:
oWater Vapour
oMethane
oCarbon Dioxide
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Description
October 12 , 2010 ASTA01H Intro to Astronomy and Astro Part I Chapter Seven: Earth Overall Structure of Planet Earth Earths mass is 6.0kg Earths radius is about 6400km o Dividing these together, we find that Earths average density is 5500 kg We can conclude that because the surface layers have densities much less than average, much denser material must lie deeper Earths interior o A thick mantle surrounds a smaller, two-part core o A relatively thin crust, compromising the solid continents and sea floor o The hydrosphere, contains the liquid oceans o An atmosphere of air just above the surface o At much greater altitudes, a zone of charged particles trapped by Earths magnetic field forms the magnetosphere Earths Atmosphere Mixture of gases: o Nitrogen 78% o Oxygen 21% o Argon 0.9% o Carbon Dioxide 0.03% o Water vapour varies from 0.1 to 3% www.notesolution.com
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