origin and evolution of the atmosphere

advertisement
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
Altitude (km)
50
Density
40
30
20
10
0
0.001
0.01
0.1
1
10
100`
1000
Pressure (mb)
.00001
.0001
.001
.01
0.1
3
Density (Kg/m )
1
10
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.
Cumulative oxygen production
EVOLUTION OF ATMOSPHERE OXYGEN CONTENT
100
80
60
40
Little
atmospheric O2
Rise of
atmospheric O2
20
0
Redbeds
Banded Iron formation
4.0
3.0
2.0
1.0
Billions of years before present
Today
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
Contrails
Precipitation
Precipitation pH
Digital Max/Min/Current
Air & Soil Temperature
Surface Temperature
Surface Ozone
Aerosols
Water Vapor
Relative Humidity
Barometric pressure
Atmosphere Measurements
Where? Atmosphere Study Site
Download
Related flashcards

Thunder gods

12 cards

Create Flashcards