Lesson Element
Glacier Mass Balance
Research Task and Exercise ‒ Teacher notes
Instructions and answers for teachers
These instructions cover the student activity section which can be found on page 4. This Lesson
Element supports OCR AS and A Level Geography.
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OCR acknowledges the use of the following content: Page 4, I mage of Lake and Glacier Trift, Image of Vatnajokull; Page 6, Image of map, U.S. Geological Survey Department of the Interior/USGS
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Introduction
Spec Link: 1.1.a
This research task relates to the glaciated landscapes topic (1.1.2) of the OCR A Level Geography
specification. The first part of this topic addresses the key idea that glaciers can be viewed as
systems, and that they experience inputs and outputs of material (snow and ice).
Later in the topic, students will study how landforms and landscapes are developed by the
erosional and depositional processes associated with the movement of glaciers. This activity will
equip them with an understanding of how the mass balance influences the advance and retreat of
glaciers and how this can lead to the different processes taking place.
The specification requires an appreciation of different spatial and temporal scales at which
processes operate. These activities address temporal variations over relatively short time scales
(variations between summer and winter) and at longer time scales (a period of 10 years). They
also relate to spatial variations at a small scale (dealing with the mass balance of a single glacier)
and a global scale (looking at the trend in global changes to mass balance).
The specification also requires students to develop quantitative skills in data handling. The
exercise requires students to calculate a measure of central tendency (mean) and a measure of
dispersion (range). Description of pattern is an opportunity for them to use qualitative data
analysis as well, which is also a specification requirement.
The final question requires cause-effect links to be established and tests students understanding of
the concept of the systems approach.
Task instructions
The research task requires students to have access to the internet. They will also, ideally, need
headphones to listen to the commentary on the video clip. If this is not possible in the classroom or
by using a dedicated ICT suite, then it could be used as a home learning task. This provides an
opportunity for some independent learning. The students are provided with a specific website
which should give them access to all they need for their research, this can be found on the student
task sheet.
The five bullet points provided should enable their research to be very focused. Instruct the
students to make separate notes for each of the bullet point questions on their task sheet.
Once they have completed the research task, they can then attempt the mass balance exercise.
They will need a calculator to do this and so you might want to tell them that the lesson before so
that they come prepared! This task should take them about 20 minutes, although the final question
gives scope for extended writing and some students may produce quite a lot of material.
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Research task outcomes
The students should discover from their research that:




Inputs (accumulation) are primarily from snowfall, although avalanches also contribute,
and that outputs (ablation) are melting and sublimation
These are measured using the exposure of accumulation layers in vertical crevasses on
the glacier surfacee by subtracting total ablation from total accumulation
If the mass balance is positive, then the glacier will increase in size and advance
downslope; if the mass balance is negative, the glacier will shrink and the snout position
will retreat upslope (the glacier itself does not move upslope!)
Globally, mass balance has decreased significantly in recent years; rising global
temperatures have led to far more ablation than accumulation.
Glacier Mass Balance: Exercise ‒ mark scheme
1.
2.
3.
4.
5.
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Total = 25.42 (1 mark), 25.42/9 = 2.82 (1 mark)
-2.60 to -4.98 (1 mark) = 2.38 (1 mark)
-0.81 (1/2 mark), + 1.21 (1/2 mark)
Overall, the mass balance tends to increase over time (1 mark), however the pattern is not
very clear and there are many variations and anomalies (1 mark). Data used as evidence
(1 mark).
The key is variation in weather conditions. This includes the amount of precipitation being
added as input, and the temperature which influences the amount of melting and
sublimation, determining the outputs. As the mass balance has increased over time, it
suggests that either there has been more snowfall and/or less melting due to lower
temperatures.
Level 1 (1-2 marks) Shows some understanding of the role of weather conditions,
perhaps just mentioning temperature.
Level 2 (3-4 marks) shows a clear understanding of the role of both precipitation amount
and temperature. For full marks, the relationship between them should be established.
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Lesson Element
Researching Glacier Mass Balance
Student Activity
Activity 1:
Lake and glacier, Alps, Canton of Berne, Svitzerland.
Vatnajokull, Iceland.
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So far you should have learnt about the formation and development of glaciers and how snow is
converted into glacier ice by the process of diagenesis.
You are now going to investigate how the size of a glacier can change over time by studying the
changes that occur to the inputs and outputs of snow and ice to a glacier. During the course of a
year the amounts of inputs and outputs vary and the relationship between the two determines
whether the glacier will increase or decrease in size during the year.
Using this website: http://www.nichols.edu/departments/glacier/mb.htm
Your job is to investigate glacier mass balance and then create a fact file to include the following:
1.
2.
3.
4.
5.
The inputs and out puts of snow and ice that a glacier experiences
How these are measured in the field
How the mass balance of a glacier is determined
How the mass balance influences the advance and retreat of a glacier
What the global pattern of mass balance has been in recent years
You will need to read the text on the website, watch the video provided and look at the photographs
and graphs that are included.
Stretch and extend: Research glacier mass balance further, is there conflicting information? What
else can you find out? Use this website as a start http://www.eoearth.org/view/article/152983/
Once you have completed the research task you can tackle the mass balance exercise on the next
page.
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Activity 2: Investigating Mass Balance: South Cascade glacier
Year
Winter
Summer
Annual
2003
2.66
-4.76
-2.10
2004
2.08
-3.73
-1.65
2005
1.97
-4.42
-2.45
2006
2.61
-4.19
-1.58
2007
3.41
-3.61
-0.20
2008
3.22
-3.51
-0.29
2009
3.12
-4.98
-1.86
2010
2.54
-3.35
2011
3.81
-2.60
Figures are metres of water equivalent.
Source: USGS
South Cascade Glacier is a small valley glacier located
in the North Cascades Range of Washington. The
glacier is situated at the head of the South Fork of the
Cascade River that flows to Puget Sound via the
Skagit River. The basin elevation spans from about
1615 to 2518 meters above sea level, and has an area
of 6.14 km2 .
You can find about more information here:
http://glaciers.us/south-cascade-glacier
Your tasks:
1.
2.
3.
4.
5.
Calculate the mean winter balance for 2003-2011. (2 marks)
Calculate the range of the summer balance figures for 2003-2011. (2 marks)
Complete the table by calculating the annual mass balance for 2010 and 2011. (1 marks)
Describe the pattern of change in the annual mass balance from 2003-2011. (3 marks)
Suggest reasons for the pattern of change you have described in Q4. (4 marks)
Total = 12 marks
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