An icy world: glaciers and glacial environments
Where is most of the world’s ice, and what forms does it take?
What are glaciers and what are the different types?
What are the characteristics of a glacial environment?
Among the many things that make the Earth a planet fit for life is the fact that surface air temperatures span a range that allows H2O to be found in all three states: vapour, liquid, and ice.
The places in the world where H2O is usually in the frozen state make up the ‘cryosphere’: this includes areas of sea ice, frozen ground, snow, and glaciers. You can learn more about the cryosphere on the Discovering the Arctic website.
The cryosphere is a very important part of the Earth’s environment, and can influence people worldwide, even those who live in warm climates, far from places where it snows.
The main reason for this is because changes in the cryosphere cause changes in sea level. More snow and ice on land means there is less water in the oceans, so sea level drops. On the other hand, less snow and ice on land causes the opposite effect, causing problems for people living along coasts as sea level rises. The cryosphere influences the Earth’s climate in many ways that will be explored in Lessons four and six.
So what are the different forms of frozen H2O in the Earth’s cryosphere? Sea ice (frozen sea water) expands and shrinks with the seasons in the Arctic Ocean and in the Southern Ocean surrounding Antarctica (this does not change sea level). Some land areas, e.g. Alaska, northern Canada, and Siberia are so cold for much of the year that soil and rock is always below 0°C and water is frozen in the ground – these are areas of ‘permafrost’. The vast majority of the world’s ice, however, is contained in the world’s ice sheets, primarily the Antarctic ice sheet.
The Antarctic ice sheet contains a remarkable 90% of the world’s glacier ice, enough ice to raise global sea level by over 60 metres! This is on the largest scale of glaciers, which come in many different shapes and size. What all glaciers have in common is that they’re formed from many years of snowfall that eventually compact to form ‘glacier ice’. The environments where glaciers are found today are called ‘glacial environments’ and these include both high latitude areas (the polar regions) and high altitude regions (in high mountain ranges such as the Alps).
Use an atlas (or go to Word Atlas website) to view maps centred on the North Pole and the South Pole. These pole-focused maps are called ‘azimuthal map projections’ because the map is drawn from a single centre point (the pole). While doing this, answer the questions on the Polar geography task download.
You can also download the Arctic and Antarctic outline maps to complete the extension activity on the Polar geography task sheet.
Open the Types of ice PowerPoint download and view the slides of different forms of ice and their locations in both polar and alpine (mountain) regions.
Go to the Discovering Antarctica website and click on ‘ice breaker’ to view the change in the amount of sea ice around Antarctica that occurs with the seasons.
Glacier ice is the type of ice which results from the piling up of many years of snowfall. In particularly cold regions where some of the annual snowfall will survive the summer, a snowfield will build up. As it thickens, upper layers of snow compress the snow below, gradually increasing its density. The sequence goes from: interlocking snowflakes full of air pockets, to denser, more granular snow (firn), and eventually to dense glacier ice several metres below the surface.
Since the glacier ice is under pressure from new layers of snow forming above, it ‘deforms’, and moves downslope. The way this works is the subject of Lesson two. In regions where snowfall is high, such as coastal mountain ranges like those in Alaska and New Zealand, glaciers can form quickly from snowfields (over several years); whereas in polar regions, where annual snowfall is low, glaciers take much longer to form (hundreds of years). Nonetheless, given enough time, glaciers can become enormous. The Antarctic ice sheet has existed in roughly its present size for about six million years. Today, about 10% of the world’s land area is covered by glaciers.
The Glaciers online photo glossary provides a list of types of glaciers, as shown below. Give a short description of each, referring to its general size and shape, as well as the type of environment where it is found.
Cirque glacier (also called a ‘corrie’ glacier)
(For more detail on different types of glaciers you can visit the National Snow and Ice Data Centre website)
The largest ice sheet in the world by far is the Antarctic ice sheet (which is subdivided into the East Antarctic ice sheet and the West Antarctic ice sheet). It covers 98% of the land area of the continent of Antarctica; and in East Antarctica, glacier ice reaches an amazing 4,776 metres thick: a thickness nearly the same as the height of Mont Blanc (the highest mountain in the Alps) above sea level.
Go to the Discovering Antarctica website and try the interactive ‘sizing up Antarctica’.
Glacial environments are, of course, cold environments. However, places with glaciers vary a lot in both temperature and snowfall. It is in the interior of East Antarctica where the coldest surface air temperatures on Earth occur: Landsat 8 satellite measurements show that temperature in this area in the Antarctic winter occasionally drops as low as -94°C! Download the Climate data task spreadsheet and do the following:
Find out the average annual temperature and calculate the total amount of precipitation for each of the three weather stations (two from Antarctica, one from Switzerland). How do they compare? Can you think of reasons for differences? (Also find their locations using Google Maps or Google Earth.)
Download the Glacier type sorting task and review the different types of glaciers.
From the climate data you looked at, you will have seen that precipitation in polar regions is very low, similar to the low levels of precipitation occurring in the world’s great hot deserts, such as the Sahara. This is why the term ‘polar desert’ is used to describe the climate of places such as the interior of Greenland and Antarctica. You could do an internet search to find the amount of annual precipitation for a hot desert of your choice and compare it with the Antarctica data.
Discuss the following questions with another member of your class:
If annual snowfall (precipitation) is so low, why are the Greenland and Antarctic ice sheets so thick?
How does cold air compare with warm air in terms of how much precipitation there can be? Can you suggest a reason?
Compare the climate data you looked at for the South Pole with the North Pole where the temperature rarely drops below -30°C (for comparison the inside of your freezer at home is about -18°C!) For what reasons is it so much colder at the South Pole than the North Pole?
From what you have learnt in this lesson about the Antarctic and its environment, write a paragraph or two about why the first expeditions to the South Pole in the early 20th century were so difficult and dangerous. The first team to reach it was a Norwegian team under the leadership of Roald Amundsen. His team arrived at the South Pole in 1911, only about a month before the arrival of the ill-fated British team led by Robert Falcon Scott which perished on the return journey.
You can learn more about the Heroic Age of Antarctic Exploration by visiting the ‘Journey South’ page of the Discovering Antarctica website.
||This resource has been developed as part of the Rediscovering London's Geography project, funded by the GLA through the London Schools Excellence Fund. It seeks to improve the quality of teaching and learning of geography in London’s schools, in addition to encouraging more pupils to study geography