UPD8

Glacial meltdown

Learning objectives

Pupils will be aware of the effects of global warming on the Himalayan glaciers and be able to formulate a plan for an exploration.

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Curriculum link

11 - 14 (KS3)
Unit 8G Rocks and weathering
That rocks fragments become sediment grains which can be transported by water currents and deposited where the energy is dissipated.

Yr8 YTO Sc1
Identify more than one strategy for investigating questions and recognize that one enquiry might yield stronger evidence than another. Recognise that a range of sources of information or data is required and use secondary sources of information.

Running the activity

Starter activity: Page 1 is a stimulus page to be projected. It sets the scene for the activity. Pupils should be given time to identify what the photograph shows and discuss the consequences of glaciers melting. There are nearly 5000 glacial lakes in the Himalayas and 44 have already been identified as potentially dangerous.

Main: Page 2 shows what a flash flood could do and sets the pupil task. They have to plan a search for problem lakes. The terms erosion and deposition could be introduced at this stage. A small overflow from a glacial lake rapidly erodes its edges and the water empties completely. On the flood plain, the water's load of mud and rocks is sorted and deposited as the torrent slows down.

Page 3 needs photocopying for each pupil. It shows the data sources pupils could use for their exploration and provides a structured template to help them decide on a strategy. Pupils could work individually or in pairs.
Factors that could make a lake likely to flood are: a high and rapidly rising water level; overhanging ice that could snap off and fall into the water, or a weak barrier holding the water in place. In order to decide what to observe, pupils need to reframe these as questions that can be investigated e.g. How does the water level change from month to month; are there any cracks in the ice above the lake; is there a relationship between the air temperature and the rate at which the water level rises in the lake. Then they consider how each data source could help answer their questions. They summarise their ideas by proposing a strategy for the exploration.

A good strategy would be to begin by using the satellite images to locate lakes that could flood heavily populated areas. A high resolution image downloadable from http://photojournal.jpl.nasa.gov/catalog/PIA03899 shows the sort of terrain these lakes are found in. A combination of aerial photography and ground surveys could be then used to verify the extent of the problem for each lake. Repeat measurements would be needed to determine the rate at which water was accumulating in a lake and pupils should be encouraged to consider graphing the results to spot the overall trend.

The lake featured on Page 1 has six times the area it had 50 years ago and threatens the lives of 10,000 villagers living 108 km downstream. A network of sensors and sirens has been set up around the lake and engineering work is being carried out to lower its water level by 30 metres.

Plenary: Pupils present their plans for the exploration to the rest of the class.

Web links

News links

BBC News

Himalaya glaciers melt unnoticed.

BBC News

Further BBC news page with lots of quotes and statistics about glacial lake outburst floods in the Himalayas.

Lake outburst

A series of photographs showing the second largest glacial lake outburst in recent times.

Nepal flood

Moving images of a glacial lake outburst flood in Nepal.

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