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History and Genealogy

HISTORY
  Big Bang
  Galaxies etc.
  The Earth
  Continents
  Ice Epochs
  Life
  Precambrian
  Paleozoic
  Mesozoic
  Cenozoic
  First People
  Europeans

GENEALOGY
  Genpics

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Ice Epochs

© 1985 by Andrew J. Morris

When the north and south poles are both open ocean, warm currents from the equatorial region warm the polar waters enough to keep it from freezing. Without ice there are of course no icecaps as we have today. These huge areas of ice brightly reflect sunlight back into space. Without the icecaps, the earth as a whole absorbs more heat from the sun, and so temperatures are slightly warmer overall.

When continents drift over the pole, or so closely surround it as to prevent warm currents from reaching the polar waters, winter snows collect into glaciers, and eventually form an ice cap. The ice cap reflects so much sunlight back into space that the Earth as a whole cools off a little bit, causing an ice epoch. These ice epochs usually last 50 to 100 million years, with fluctuations during that time so that the glaciers advance and recede. Such an ice epoch occurred about 700 million years ago. All of the continents were combined into one huge land mass we call Pangaea I, wich drifted into one of the poles about that time.

The about 600 million years ago Pangaea I broke up into four separate continents. Some 300 million years ago the four continents coalesced into one again, which we call Pangaea II. This massive continent drifted over the south pole 250 million years ago, triggering another ice age. About 200 million years ago Pangaea II begn to break up into the seven continents we have today.

The current ice epoch begn about 10 million years ago. By that time Antarctica had drifted over the south pole. The distribution of continents in the northern hemisphere served to block the warm equatorial ocean currents from reaching the north pole, so that ice covers that pole too now.

As mentioned before though, temperatures fluctuate during an ice epoch, and the glaciers advance and recede accordingly. We are currently in one of the warmer spells between ice advances -- an interglacial. All of the social and technological advances that we attribute to civilization came about during this current interglacial period. The ice will probably come creeping back into North America in just another 10,000 to 20,000 years.

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