Glaciers as a Hazard

I would just like to point out a really useful book that has helped me out greatly in this section and the next section. Its by a gentlemen called Peter Knight, who is an University Professor at the University of Keele. I read his book Glaciers (1999) however he has done many other academic writing and published more recent work.

In this section, I am going to write about how Glaciers are classed as a Hazard.

Ice Avalanches

Ice avalanches occur in a similar fashion to landslides and snow avalanches. In some cases Ice avalanches occur in conjunction with landslides and snow avalanches but also with other natural hazards such as earthquakes.

When Ice breaks away from the main Ice sheet, whether its by an earthquake or where the ice has moved past the bed rock underneath, the affects are disastrous. With modern technology and the Glaciers slow movement, their movement patterns are fairly predictable and are fairly rare. However when Ice Avalanches have happened its been at a great cost.

On the 10th of January 1962, a mile and a half long chunk of Ice separated from the 180 foot thick ice cap in the Nevados Huascaran valley in the South American Andes. The 4 million tons of Ice fell down the mountain, bringing with it, dirt and rocks from the slopes. In the space of 15 minutes, the ice avalanche travelled 11 miles. Once the avalanche had stopped the realization of the disaster was truly appreciated, a total of 7 villages were buried under the snow and a death toll that scientists can only estimate of around 4,000 people.

There was an avalanche in 1970 in the same area of Peru, that was the most catastrophic rock-ice avalanche known in history. That was caused by an earthquake with a magnitude of 7.7, this avalanche was huge in size and claimed the lives of 18,000 people.

Below is an image that shows the distance the two avalanches covered:-


http://maps.grida.no/go/graphic/ice-avalanches-of-the-nevados-huascar-n-in-peru

  Please use the links below to see more about the case studies:-

UNEP websitehttp://maps.grida.no/go/graphic/ice-avalanches-of-the-nevados-huascar-n-in-peru

and also
http://library.thinkquest.org/C003603/english/avalanches/iceandrock.shtml

Floods and Lahars

Glacier floods are considered among the most damaging hazards as they are an outburst of a vast amount of water. Also Glacier floods are very unique to each individual Glacier and may not cause any damage for years. Like Avalanches, Glacier floods can be caused by a numerous amount of reasons. In the Swiss Alps, Glacier floods occur approximately every two years by an outburst from ice-marginal lakes and the rapture of water pockets with in the Glacier.

However the a recent Glacier flood happened in Iceland on April 14th 2010 and began for a totally different reason. I will be writing about this Glacier as one of my in-depth case studies. Please see a future post...

Fluctuations and Surges

In an era when our climate is rising, it is unusual to think that any Glacier would be growing or surging forward. However this was a major hazard during the little Ice Age between the 13th and 19th Century.

The early settlers in Iceland, set up new settlements near Glaciers and when the Glacier grow it demolished the newly built towns. In modern development there is a proximity zone around Glaciers to prevent this hazard from occurring.

 As Glacier movement is slow and predictable, growth is not considered a immediate problem, however surge can be quick and surprising. A surge is a short lived event when a large amount of ice moves or slides forward, this can cause other hazards such as flooding.

The above image shows the surge of the Medvezhiy Glacier in Tajikistan, from June 3rd 2011 to 23rd of July 2011 the Glacier slid abruptly around 800 - 1000 metres. The Glacier normally moves around 200 - 400 metres a year. Glaciologists are concerned about Glaciers outbursts, as the Glacier is now blocking the Abdukagor River. It is causes a lake behind the ice sheet, infrastructure has already been damaged by one outburst already.

Please see the link to the Earth Observatory website below for more details on this case study:-

http://earthobservatory.nasa.gov/IOTD/view.php?id=51498 

Tasks for students:-

I think that it is really important that students do not just see these hazards as a physical occurrence. Using mind maps, I want the students to think carefully about have these hazards do impact on humans.