Causes and Formation of Glaciers

Causes of Glaciers

There are many theories as to the cause of glaciations:

Milankovitch cycle – changes in incoming radiation due to changes in orbit, tilt and position in space.
Variations in sunspot activity
Changes in the amount of carbon dioxide in the atmosphere
Changes in the movement of the ocean currents
Periods of extreme volcanic activity which put huge amounts of ash into the atmosphere

Formation of Glaciers

During the onset of a glaciation, more and more precipitation falls as snow.
In addition, less and less snow melts each summer so that successive layers of snow gradually build up until there is a year-round snow cover in more and more places.
Fresh snowflakes trap much air and have a low density.
As snow becomes more compacted, the air is driven out and density increases.
Eventually, this process forms neve or firn (compacted snow).
After 20-40 years the firn will turn into glacial ice which contains little air and has a density of about 0.9.
Glacial ice can begin to flow downhill under the influence of gravity as a glacier.

This video looks at the formation of glaciers

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