Break up of Pangea

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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 the atmosphere.

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.

Climate Change:

• Periodic Ice Ages ---> Glacial-Interglacial Periods
  • 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

  We currently are nearing the end of a small, minor interglacial period

• Major Ice Ages: Most of the Planet is Covered
• Minor Ice Ages: 40^o 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)

Effects of Ice Ages

• Changes sea level by 100 meters exposes continental shelfs
• changes continental shelf composition due to increased deposition during melt
• 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

Causes of Ice Ages --> needs to be PERIODIC!

• 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 land masses
• 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

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The Electronic Universe Project

e-mail: nuts@moo.uoregon.edu