Asked by robert to Anna, Daniel, Denise, Jesse, Rehemat on 24 Jun 2014.
Keywords: cause, glaciation
Glaciations are generally caused by changes in the earth’s orbit, so changes in its tilt and therefore the amount of solar radiation it receives from the sun.
From about 1450 – 1850 there were changes in solar insolation and there was a Neoglacial period known as the Little Ice Age.
I think Rehemat got part of it, but I think a more important aspect of what causes glaciation is the movement and breakup of continents. These movements significantly affect oceanic and atmospheric circulation. For example, plate-tectonic movement could causes continents to be blocked off from each other so that warm water flowing from the equator to the poles is blocked or reduced and ice sheets could form, setting another ice age in motion. An example of this is the uplift of the Himalayas which changed atmospheric circulation patterns and initiated a large glaciation event.
Another important factor is volcanic input of CO2 to the atmosphere.
you got some nice replies already, I will add then another possible cause of global glaciation, although a less severe one!
After volcanic eruption, volcanic ashes can strongly interact with the atmosphere and the clouds, changing the amount of solar radiation that gets to the ground, and in turns, affecting temperatures on land.
For example 1816 is famous as “the year without summer”, because of a combination of low solar activity and some big volcanic eruptions, that injected in the atmosphere a lot of volcanic ash.
As I understand it global glaciation refers to the Hypothesis of Snowball Earth where the most of the surface of the Earth was covered with ice. This may have happened 650 million years ago. There are glacial deposits in all continents in rocks of this age and there are striations produced by the movement of rocks within glaciers preserved on that time. It is interesting that these rocks are suggested to form in the tropics according to paleomagnetic analysis of the rocks. So there were glaciers in the tropics everywhere else!
It seems that the concentration of carbon dioxide had a lot to do with this event. When there is a lot of precipitation due to warm climate, there is a lot of weathering and erosion which moves carbon dioxide in the water and rocks to the oceans. There, it is precipitated in and forms limestone where it is stored away from the atmosphere. That would result in less carbon dioxide in the atmosphere and less greenhouse effect, thus cooling the atmosphere. In the case of Snowball Earth, there may also be a contribution of the distribution of the continents to produce more weathering and erosion.
I do remember a paper which explained the global glaciation perfectly and probably, I could not explain it as well as they did.
Have a read of this paper: http://www.princeton.edu/main/news/archive/S27/26/54A51/index.xml?section=topstories
Hope it helps! 🙂
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