Origin evolution and nature of the atmosphere by GU9jBy8C

VIEWS: 1 PAGES: 9

									     WHY STUDY THE ATMOSPHERE?
1. The atmosphere is a major component of the Earth System,
   because it
         a. helps distribute energy over the Earth (moving air
   masses,major circulation patterns, origin of climatic deserts)
         b. is where weather is made (predict what weather will be
   tomorrow, next week, etc.; What should we wear?)
         c. controls how our homes and other buildings must be built
   (air conditioning, heating, insulation, etc.)

CHANGES IN THE ATMOSPHERE CAN BE BENEFICIAL OR DEADLY.

2. Changing atmospheric conditions can cause major modifications
   in both weather and climate, affecting how and where humans
   can produce food.

3. Our atmosphere is unique in the solar system. Earth is the only
   planet on which we can survive without a space suit—we have
   evolved to function in our atmosphere, not on Mars or Venus.
   Commonly Accepted Definitions
Weather refers to the current atmospheric
 conditions (including temperature, precipitation,
 wind, humidity, barometric pressure) at a
 particular time and place.

Climate refers to the general weather patterns
  expected in a given area (sometimes based on
  the 30 year average weather). Climate may also
  be applied more generally to large-scale weather
  patterns in time or space (e.g., an Ice Age
  climate or a tropical climate).
Weather is made in the Troposphere
                90

                80

                70

                60
                                               Pressure
                50

                40            Density
Altitude (km)




                30

                20

                10

                 0
                     0.001    0.01    0.1      1       10   100`   1000
                                        Pressure (mb)

                .00001       .0001    .001    .01     0.1    1      10
                                     Density (Kg/m 3)
ORIGIN AND EVOLUTION OF THE ATMOSPHERE
● Early atmosphere [H, He, Ammonia (NH3) and Methane (CH4)] was
driven away by solar radiation and lost by their low atomic masses
● Primordial Earth melted completely and gases bubbled out or
erupted from early volcanoes. Result was a N-rich atmosphere
● Evolution of blue-green algae changed everything! Photosynthesis
by these algae absorbed CO2 from the atmosphere and released O2
● Most of that oxygen was dissolved in the oceans where it combined
with iron and precipitated until about 2.5 billion years ago (2.5 Ga) to
form iron oxides in banded iron formation
● At about 2.5 Ga, oceans were saturated with oxygen and free oxygen
was added to the atmosphere. Resulting surface oxidation produced
first redbeds on the continents.
●At about 1 Ga, reservoirs of oxidizable rock at the surface were
saturated and oxygen began to build up in the atmosphere
● Ultraviolet light split O2 molecules forming ozone (O3) that shielded
the surface from intense solar radiation. At that point, life could
emerge from the ocean and colonize the continents.
EVOLUTION OF ATMOSPHERE OXYGEN CONTENT

         Cumulative oxygen production   100

                                        80

                                        60

                                        40
                                                        Little            Rise of
                                                    atmospheric O2     atmospheric O2
                                        20

                                         0                                                  Redbeds
 Banded Iron formation
                                              4.0       3.0      2.0        1.0         Today

                                                Billions of years before present
   EVIDENCE FOR ATMOSPHERIC EVOLUTION
    COMES FROM THE GEOLOGIC RECORD
   Banded iron formation (3 Ga)                   Continental redbeds




Until about 2.5—2.0Ga, there was not enough oxygen in the atmosphere to
oxidize iron minerals. Oxygen dissolved in the oceans oxidized iron to produce
marine banded iron formation.
At 2.5—2.0 Ga, enough oxygen accumulated in the atmosphere to oxidize iron
on the continents and the first redbeds formed.
      Atmosphere Protocols
Cloud type and cover      Surface Temperature
Contrails                 Surface Ozone
Precipitation             Aerosols
Precipitation pH          Water Vapor
Digital Max/Min/Current   Relative Humidity
 Air & Soil Temperature   Barometric pressure
Atmosphere Measurements




    Where? Atmosphere Study Site

								
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