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