What are glaciers and how are they formed?

Glaciers are made up of layers of fallen snow that over many years has been compressed. This compression causes the snow to re-crystallises into granules similar to that of sugar. Over time the continued compression of the snow reducing the air pockets between them as the crystals become larger to form large ice masses. They currently occupy 10% of the earth’s land mass and are mainly found in Greenland and Antarctica.

These are a particularly interesting aspect of snow and ice as they have the ability to move. When ice is put under this large strain the ice will fracture. Water is a substance that under pressure lowers the temperature the solid to liquid transition takes place at, in this case sub-zero. This causes a lubricating film of water to form under the glacier, which along with gravity and the weight of the ice causes it to flow downhill. Movement along the underside of the glacier is slower than the top due to the friction made by the grounds surface.

Here is an experiment that could be used to demonstrate the flow of a glacier.

Flubber Experiment

Materials

·         Warm Water

·         White Glue(Elmers)

·         Borax

·         PVC pipe cut in half

·         Clingfilm

·         Cooking Oil

·         Sandpaper

·         Ruler

·         Freezer/ Microwave

Firstly create two mixtures the first consisting of a ¾ cup of warm water and 1 cup of glue. The second is made up of 2tbs of borax and ½ a cup of warm water. Next combine the two together and work through the hands until a consistent texture is reached.

 The children can then experiment with what can influence the speed / flow speed of the glacier. They could change the independent variable to; steepness of the slope, temperature of the flubber or even the conditions at the base of the flubber in order to experiment what the effects could be.

Glaciers often have rocks and debris underneath them which can restrict flow this could be demonstrated with the use of sandpaper which will significantly increase friction. Similarly some glaciers have a thin film of water underneath them. This can be modelled by smearing cooking oil over the PVC tube. By experimenting with all this different ideas the children can begin to grasp the idea of just how glaciers move in a fun and hands on way.

How far south did glaciers come?

Whilst glaciers in England only reached as far south as Oxfordshire around the world glaciers came so far south that they actually appeared in the tropics. The tropics are defined as 30ºN and 30ºS latitude. Some examples of glaciers in this area are Yanapaccha glacier, Peru and the Elena glacier near the Republic of Congo and Uganda border. However, as you can see from the pictures below they are rapidly depleting.

Elena Glacier 1906-1994

Could the South Downs have been affected by glaciation?

125 million years ago the south east was covered with fresh water lakes and rivers which carried clay building up layers at the base of the river. Soon after the sea began to break through laying down chalk made up of skeletons of dead sea creatures this created the bases of the South Downs.

The South Downs were originally formed by two tectonic plates (Eurasian and African plate) colliding the pressure at the point of impact caused the area to be upwards creating mountain chains. This is called alpine orogeny.

 Whilst no glaciers reached the South East the tundra like conditions which can be found on the edge of ice sheets dominated this area. As Carter states “Frozen chalk prevented further absorption.”(1990) this meant that the summer rain and melt water formed streams which carved out valleys. As the climate rose the water began to soak through the chalk which is an example of an aquifer which is a type of rock with small holes like pores which allow water to soak through leaving what is called dry valleys.

So in answer to the question posed whilst glaciers did not cause the formation of the South Downs . The freezing cold temperatures caused by the Ice age did however, aid the erosion process which shaped the already existing South Downs.

Resources I Used.

·         http://www.weatherquestions.com/What_causes_glaciers.htm

·         http://nsidc.org/cryosphere/glaciers/questions/what.html

·         http://www.realclimate.org/index.php/archives/2005/05/tropical-glacier-retreat/

·         http://www.southdowns.gov.uk/learning/themes-to-study/landscape/geology/geology-through-time

·         http://www.naturalengland.org.uk/ourwork/conservation/geodiversity/englands/counties/area_ID34.aspx

·         Timothy Carter (1990) Encyclopaedia of Brighton