Break up of Pangea
Climate results from the uneven distribution of heating over the
surface of the earth caused by the earth's tilt. This tilt is
the angle between the earth's rotational axis and its orbital
plane around the sun. Currently this angle is 23.5 degrees.
Long term climate is also affected by the heat balance of the earth
which is driven mostly by the concentration of CO2 in
Climate change can result if the pattern or solar radiation is changed
and/or if the amount of CO2 changes. There is abundant
evidence that the earth does undergo climatic change. Climatic
change can be a limiting factor for the evolution of many species.
Effects of Ice Ages
- Periodic Ice Ages ---> Glacial-Interglacial Periods
We currently are nearing the end of a small, minor interglacial period
- Major Period: ---> 100,000 years; 9 degree F decrease
- Minor Period: ---> 12,000 years; 5 degree F decrease
- Smaller Periods??: ---> 1,000 years; 3 degree F decrease
Major Ice Ages: Most of the Planet is Covered
Minor Ice Ages: 40o Latitude and Above. The most
recent one of these occurred about 15,000 years ago and the
coverage of the ice sheet is shown here
Little Ice Age: (1000-1850 AD; Irish Potato Famine; Nisqually Glacier)
Causes of Ice Ages -->
needs to be PERIODIC!
Changes sea level by 100 meters exposes continental shelfs
changes continental shelf composition due to increased deposition
changes hydrological cycle through less evaporation
changes landscape Great Lakes; Seattle; Stoss and Lee
Changes drainage patterns
changes topsoil characteristics
massive flooding episodes --> Eastern Washington
Solar Cycle --> no evidence
Volcanic Dust in Atmosphere --> why periodic?
CO2 Cycle --> why periodic? --> factor 2 reduction
causes 7 F drop --> Record of CO2
and temperature variations
Increased precipitation at poles due to changing orientation of continental
Changes in mean temperatures of ocean currents --> what mechanism?
The most Probable Cause:
Orbital Variations of the Earth!
- Eccentricity variation 90,000 years 5 variation
around mean value. This is due to Jupiter.
- Change of tilt of axis 24,000 years
More About Ice Ages
More about orbital mechanics and Ice Ages
The Electronic Universe Project