Glacial environments - Where in the world is the ice?
This lesson explores where in the world we can find glacial environments.
- Where is all the ice?
- Are there different kinds of glacier and how do they change over time?
- In the distant past, were ice sheets bigger or smaller?
- Why did the earth used to be colder?
- Physical Environments
Where is all the ice?
Ninety per cent of Earth's ice is found here. The ice here is sometimes over 4000-5000 metres deep.
North America (including Alaska)
One of the world's youngest glaciers is growing here, in the crater left when Mt St Helens exploded in 1980. The ice here contains perfectly preserved woolly mammoths and other animals from 10,000 years ago.
Scientists are worried about the massive glaciers found in the Andes mountains. They think global warming is causing them to melt more quickly.
Greenland is really shaped a bit like a doughnut but the outline of the ice prevents us from seeing this on most maps. If all the ice melted, world sea-level would rise by seven metres. Greenland, like Antarctica, is very important global ice store.
Climate change means Europe's glaciers are melting so quickly that they may have vanished by 2050.
Asia (including Russia)
Hundreds of millions of people depend on summer meltwater running off the Himalayas (where Mount Everest is found) for their drinking water supplies.
Africa (and Middle East)
In Africa, there are glaciers on the equator. Kilimanjaro is so high that it is still cold enough for ice.
Australasia (Australia and New Zealand)
New Zealand's glaciers were the setting for the films of Lord of the Rings (teacher's tip: show an extract from the DVD of the film if you have access to one, or image search using Google)
There are different kinds of glacier and they change over time
Eighty five per cent of the world's ice is found in the giant Antarctic ice sheet
This ice sheet would cause the earth's oceans to rise by seven metres if it melted.
Ice caps cover less area than ice sheets. The Himalayan ice cap is home to Mount Everest, the world's highest mountain
Individual valley glaciers like those found in Switzerland are much more accessible to people and attract skiers and snow-boarder
A corrie glacier is a small glacier that has developed high up on a sheltered mountain-side
A glacier can start life as a tiny snow-patch is only metres wide that only just barely survives the warmer months of summer. However, once a small amount of snow has survived the whole year, glaciers can grow very quickly. The glacier formed in the crater at Mount St Helens is less than 30 years old but already well over 200m deep in places.
Glaciers change size over different timescales
Whenever snowfall exceeds rates of melting, a substance called firn develops as snow is compressed to eventually become dense ice. This is helped by melting and re-freezing (the same way ice on roads sometimes develops) so that most (but not all) air is removed. Rivers of ice begin to flow downhill under gravity. Glaciers move forwards into lowland regions where warmer air brings melting. The size of the glacier is thus a function of snowfall and air temperatures.
Melting glaciers are observed to be retreating. Their front end (the snout) recedes up-valley. This is happening to many glaciers today on account of climate change. However, the mass of ice is still moving downhill. But melting is taking place in lowland areas at a faster ice than new ice (from fresh snowfall in highland areas) moves down slope to replace it. It is like an escalator that is having pieces removed from it. Although it never stops moving downwards, the length of escalator is getting smaller as pieces are taken away.
This is a complex area for non-specialist teachers who may want to consult textbooks aimed at an older A Level audience.
In the distant past, ice sheets used to be bigger
There have been many cold phases called ice ages. Some scientists believe that the coldest chapter of Planet Earth's took place 700 million years ago. They describe it as the "Snowball earth" era. Our last major cold period, the Pleistocene, started 1.8 million years ago and ended just 10,000 years before the present day. Since then, conditions have been warmer. This most recent 10,000 years is called the Holocene. The Pleistocene and the Holocene are part of the Quaternary Period of Earth history.
Gifted and talented geographers might want to know more about the scientific explanations for past climate change, for example Milankovitch curves. According to Milankovitch (a Serbian physicist), every 100,000 years or so the Earth's orbit changes from a circular to elliptical (egg-shaped) pattern. This changes how much sunlight we receive. He also identified that the Earth's axis moves and wobbles about, changing over 41,000 and 21,000 year cycles. This also effects how much sunlight is received. Put all of this together and the history of ice ages can be explained.
Why did the earth used to be colder?
Four propositions: Which is definitely false?
Earth's orbit around the sun changes shape
Thought to be true. This is called the Milankovitch Theory and it states that there are changes in the earth's orbit that sometimes take it further form the sun, resulting in cooler temperatures on earth.
Mountains grow too high
Could be true. Earth's continents move and occasionally collide with one another (this is called plate tectonics). When India collided with Asia, land was forced up to form the Himalayas. A complex series of events followed that changed Earth's climate and may have caused cooling.
The sun gets too spotty
Known to be true. Regions of the sun's surface sometimes drop to a lower temperature causing dark spots to appear on its surface. This results in slightly less sunlight reaching earth which can cause cooling.
Too many volcanoes
Known to be true. major explosions lower global temperature due to high-altitude ash clouds reducing incoming solar radiation.
Too much carbon dioxide is added to the air
Definitely false. The opposite is true. Past periods of cold coincide with times of less carbon dioxide rather than too much (as is becoming the case in modern times).
Where is all the ice?
Study a world map or atlas.
Can you identify which areas are covered in ice?
Which continents have the most ice?
Which continents have the least ice?
How does the scale of glaciers vary in different places?
The where is the ice PowerPoint presentation will give you some facts and figures about the world's ice cover.
What does the ice sound like?
Listen to some of the sounds of cold environments and glaciers.
How has ice cover changed over time?
For the main part of the lesson, you have three key questions to answer to explore how global ice cover has changed over time. You will use a range of websites and resources to answer the questions.
What types of glaciers are there and how do they change over time?
Read the types of glaciers document which introduces you to some of the different types of glaciers that exist.
Use the document to help you to describe the following types of glaciers:
- Ice sheets
- Ice caps
- Valley glaciers
- Snow patches
Can you find examples of each of these types of glaciers on Google Earth?
Now use the document to explain how glaciers change over time, and divide the causes of change into physical (natural) and human (caused by people) effects.
How do glaciers change in size over time?
Have a go at the interactive activity to find out how glaciers change in size over time.
What are the main factors which cause the glacier to change in size?
What is an Ice Age, what causes it and how was the UK affected by the last Ice Age, which ended 10,000 years ago?
Read the Ice Ages document which tells you about Ice Ages, periods of the Earth's past when temperatures were much colder than they are today. The last Ice Age was called the Pleistocene. It started 1.8 million years ago and ended 10,000 years ago. Since then we've been in a much milder period called the Holocene.
Complete the true or false activity on the sheet which looks at the possible causes of such extreme natural change in the Earth's temperatures.
As a homework task, use the Internet to find out how much of the UK was covered by ice during the Pleistocene Ice Age. A map of the British Isles is provided for you on the Ice Ages document.
Ice Age history
Did you know? 18,000 years ago, the UK and France used to be joined together.
How do you think our lives would be different if the two countries were still joined? How might the following things be different?
What do you think has happened since this time to separate the two countries?