Ecology And Environment

Possible causes of the Recurrent Ice Ages

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"Possible causes of the Recurrent Ice Ages"
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According to scientists, the planet earth encounters cyclical cold extremes, which we have come to know as ‘ice ages’. In the 1920s, a mathematician named Milutin Milankovitch postulated a theory to describe this phenomenon based on several factors which later became known as ‘Milankovitch cycles’. Thus, Milankovitch calculated the intervals between potential ice ages taking into account the earth’s axis, the earth’s wobble on its axis as well as the earth’s closeness to the sun. Accordingly, he predicted ice ages to occur every 22,000, 41,000 and 100,000 years.

Therefore, the major determinants of the recurrent ice ages would be the amount of solar radiation reaching the earth at a particular time period. To be more specific, the intensity and the timing of the heat would determine if the earth is to become cold or warm.

When looking at the ‘earth’s wobble,’ it should be understood that, the earth is tilted on its axis at a 23.5 degree angle on each side of the axis which makes it to wobble during spinning. The complete range of motion on the tilt takes about 41,000 years, which explains one of Milankovitch’s postulated ice ages. Because of the earth’s wobbling, its position on the elliptical path around the sun will also change relative to the time of the year. These changes will also take place in a cycle and is known to the scientists as the ‘precession of equinoxes’. As each precession of equinoxes take place over 22,000 years, it explains the Milankovitch’s 22,000 year prediction for manifesting a ice age. The reason for Milankovitch to predict an ice age every 100,000 years was because the earth’s orbit will also change from a extreme circular orbit to a extremely elliptical orbit, in which case the radiation received from the sun would be extremely low. The change of orbits from circular to extreme elliptical is postulated to take place every 100,000 years and therefore Milankovitch predicts an ice age to occur at 100,000 year intervals as well.

Apart from these three factors, scientists believe that the movement of earth’s plates or plate tectonics will also play a vital role in changing the climates. For instance, because of the collisions taking place between these plates, mountain ranges can form and these high altitudes are conducive to promote colder climates than low altitudes. As such, the changes in the earth’s composition could also bring about a climate, which is much more conducive towards the formation of glaciers.

Another aspect that may contribute towards an ice age is the diminishing levels of atmospheric gases. It is believes that, gases such as carbon-dioxide and methane will trap energy closer to earth and therefore will keep the planet warm and during ice ages, these gases have seen a dramatic drop although scientists are unable to explain why such a drop took place in respect to ice ages.

Furthermore, high levels of dust such as those released from volcanic explosions can also make the planet cooler by blocking the sun’s rays through various chemical reactions between the dust particles and the water vapor. Sunspot activities have also been linked with the climate changes taking place in the earth and according to scientists, having high degree of sunspot activities makes the earth warmer than at times of low sunspot activities.

Thus, it is apparent that, many factors contribute towards cooling of the earth and therefore the occurrence of an ice age is a collaborative effect of all these factors, although some factors will have a far-reaching effect than the others.

More about this author: Dr Pandula Siribaddana

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