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The Ice Age

Ice Ages are most likely caused by variations in the intensity and timing of the heat from the sun which cause glacial/interglacial cycles. Serbian scientist Milutin Milankovitch described this in 1938. There are three major components of the Earth's orbit around the sun that contribute to changes in our climate. First, the earth's spin on its axis is wobbly, and variate up to as much as 23.5 on either side of the axis. The tilt in the Earth's rotation affects the amount of sunlight hitting the different parts of the world. The greater the tilt the greater the difference in the seasons. The range of motions in the tilt{left-of-center to right-of-center and back again} takes 41,000 years to complete. Asa result of a wobble in the Earth's spin, its position on its elliptical path changes relative to the time of year. This is a phenomenon called the precession of equinoxes.

The cycle of equinox precession takes 23,000 years and in the growth of continental ice sheets summer temperatures are probably more important than winter.Ice Build Ups-When summers are too cold to allow snow to melt from previous winters.{summers that occur when the sun is at its farthest point in Earth's orbit}. When this continues for centuries, ice sheets begin to form. The orbit of the Earth also begins to change. At one extreme of this, when the orbit is more circular, each season recieves the same amount of solar radiation. At the other extreme, the orbital ellipse is strecthed longer and exaggerates the difference between the seasons. The eccentricity of Earth's orbit also proceeds through a long cycle, which lasts for 100,000 years. Major glacial events have coincided with the phases of the Earth's tilt, precession of equinoxes and eccentricity of orbit which are lined up to give the northern hemisphere the least amount of summer solar radiation.

Presently, 10% of the world's total land area is ocuppied by glaciers with most of them located in Antarctica or Greenland. Glaciers have been around since the Ice Age, when ice covered about 32% of the land and 30% of the oceans. An Ice Age is a period when cool temperatures allow polar ice to advance into the lower latitudes. During the last Ice Age on Earth, huge sheets of glacial ice covered all of Canada, Scandanavia, Scotland, and parts of New York State. Within the past 750,000 years, scientists have learned that there have been eight Ice Age cycles with warmer interglacial periods between them. Right now, the Earth is at the end of an interglacial period and will experience another Ice Age in a few thousand years. This is part of the normal cycle of climate change. Glaciers also serve as signs of possible global climate


What Are Glaciers? | How are they formed? | What are they Made of? | Where can they be found? | Erosion | The Ice Age | Famous Glaciers | Features | Glaciers and People | Interesting Facts | Bibliography