It was great discussion ignited by Teacher LL. It spread the heat on to various directions and ultimately turned hot when it turned to Global Warming (GW) topic. It burned out many things in the process. Of course later, it also inspired a classic essay by Amit about the Struggle of three of elements of nature. Of course, it generated enough amount of discussion, but remained in controlled temperature and pressure!

Recently I heard a news item in CNN about the weather report which mentioned that average temperature recorded during 2008 is lowest in many years. This and experience of  outcome of “Y2K Disaster” theories provoked me change the gear and go back to text books. I also tried to read materials which do not exactly agree with view of GW proponents. I have jotted down the points and at many places removed the complex explanation to simpler language. Of course, I have done lot of cut and paste from multiple resources.

If any one is interested, I suggest reading the article on the link http://www.geocraft.com/WVFossils/ice_ages.html. It is quite elaborate. One can get deeper with the links inside the article and if anyone wants to go further deep, please refer to any classical Geology reference book.

Earth came to current stage from the molten rock stage. Last confirmed repeatable test of age of earth is around 4500 MM years. (MM stands for million). Life is confirmed to have started appearing around 600 MM year. This is called the Cambrian period. Anything before this is called Precambrian.

After earth started cooling down, as per the geological evidences the Ice age occurred much before the life appeared on the earth. Since then it is cycles of cooling to Ice age and warming up to rise sea level in the geological history of the earth. Earth's climate and the biosphere have been in constant flux, dominated by ice ages and glaciers for the past several million years. We are currently enjoying a temporary reprieve from the deep freeze.

Why the cycle of Ice age and Warming happens on the earth? Why the sea level changes? If the sea level changes are so disastrous, how the life has survived on the earth? Philosophically, why nature destroys its own creation? Am I so powerful to change natural course of action?

Let us see the reasons for temperature changes through geological ages.

Astronomical causes:

11 year and 206 year cycles of Solar variability

21,000 years cycle of earth’s combined effect of tilt and elliptical orbit around the Sun.

41,000 year cycle of +- 1.5 degree wobble in earth’s orbit

100,000 year cycle of variation in shape of earth’s elliptical orbit

Atmospheric Causes

Heat retention: Due to atmospheric gases, mostly gaseous water vapor (not droplets), also carbon dioxide, methane, and a few other miscellaneous gases-- the "greenhouse effect"

Solar reflectivity: Due to white clouds, volcanic dust, polar ice caps

Tectonic Causes

Landmass distribution: Shifting continents (continental drift) causing changes in circulatory patterns of ocean currents. It seems that whenever there is a large land mass at one of the Earth's poles, either the north pole or south pole, there are ice ages.

Undersea ridge activity: "Sea floor spreading" (associated with continental drift) causing variations in ocean displacement.

I will present the sea level changes in the geological history and what is written in stone for our future in the next installment.