New Perspective

Whilst on my placement at the secondary school I managed to get access to a variety of text books that were used for A-levels. Within this I managed to find a small bit of information that I hadn’t previously thought about.

When teaching the subject it would be good to emphasise the relationship between glaciers and periglacial environments. They are often superimposed one on top of the other; as an ice sheet begins to retreat the space it leaves behind becomes exposed to perglacial conditions and processes. And then as glaciers advance the periglacial environment becomes glacial once again. This process recurs and can a mixture of these two environments can be seen across Northern Britain.

One other thing that I had not previously thought about was how this topic could be incorporated into other topics – especially biogeography. Recent observations lead me to realise that a good way to maybe more fully engage pupils with a topic quite alien to them would be to examine the biogeography involved in this region – the tundra. Getting students to look at this and look at the different fauna and flora as well as climatic conditions could help them to get used to the environment we would be examining and set the scene a bit better for them.

For example, maybe starting with biogeography and then leading into the topic of periglacial environments could be more beneficial for students. It did help me to put things into perspective when I looked at the different conditions and processes from this perspective as it was something that I was more familiar with. Basing it on this, for some pupils it could be much easier for them to understand the topic and hopefully they could gain more from the lessons.

Periglacial environments and human activity

I have found it very difficult to find information relating to human activity in periglacial environments. Most information I have found mostly relates to glacial environments or periglacial environments and climate change. However, I have still managed to find some information which relates to human activity within periglacial environments.

First of all, it is important to outline the challenges that humans face in this physical environment:

- Very low temperatures

- Low precipitation rates

- Short summers which means short growing seasons

- Presence of permafrost

- Thin, poorly developed soils

- Long periods of snow on the ground

- Blizzards

- Waterlogging in the summer due to the thawing over permafrost layer

When teaching this, it would be good to ask the class for ideas of the challenges humans would face in periglacial environments given what they have already learnt about them. Putting this list up on the board would be a good start and then you could ask students to work in pairs to come up with some problems humans may face, for example building settlements, getting food etc.

The Problem

The main problem of living in periglacial environments is soil temperature. Almost every human activity involves the production of heat which can have a detrimental effect on the underlying ground – the heat may melt the underlying permafrost and so lead to a thermokarst landscape.

The Solution

Houses – those that are built in these environments are raised up and off of the ground on wooden piles. This then allows for air circulation between the building and the permafrost to avoid heating the ground. The piles are cemented in and allow for the contraction and expansion of water which makes them more stable throughout the year.

Roads and runways – These may be made of gravel which prevent large amounts of heat from being transferred to the ground. Runways and some roads are also painted white to reflect solar energy which stops heat from being transferred to the soil

Pipes – The problem of moving sewage and water through these environments has been solved through the creation of utilidors. These are insulated boxes which are raised on low pilings carrying pipelines for water supplies, sewage pipes, heating pipes etc. They have to be above ground as if they were buried they would freeze and would also be affected by the seasonal thawing and freezing in the active layer.

Human impacts

All of these methods that have been created to allow humans to live in this environment can have negative effects. In order for settlements to be established, ground is often cleared which results in a reduction of insulation and in the summer then results in a deepening of the active layer. With regards to transport, there is a risk of oil spills and vehicles damaging vegetation around the area. Another major impact is that of over-hunting. As many populations rely on native wildlife for food, continuous hunting of the same animals may eventually lead to a reduced population and thus have a negative multiplier effect on other wildlife species and vegetation.

This work on human activity could be made more enjoyable for students by getting them to create spider diagrams and mind maps, for example:

The diagram above is one I made as an example of what the pupils could create to develop their ideas. Red arrows indicate the problems and green arrows indicate the solutions to these problems. Pupils may find some ideas over lap and is good to get the students engaged with the topic.

Periglacial Landforms

Now that I have gone through the processes that occur in a periglacial environment, I am now going to focus on the landforms that are created as a result of this.

Pingos – These are one of the common features of a periglacial environment and are created as a result of frost heaving. Pingos are dome shaped hills (with an ice-core) which can be between 3 meters and 7 meters in height and can be up to 1,000 metres in diameter.  Pingos fall into two categories: closed-system and open-system.

Pingo in the Arctic

            Closed-system: These form in areas where unfrozen groundwater becomes trapped by permafrost which puts pressure on the surrounding soil pores and forces the water inwards. As temperatures drop, the water freezes and expands, causing the frozen soil above to be forced upward, creating these mounds.

            Open-system: These are usually smaller than closed-system Pingos. These form when groundwater flows downhill and becomes trapped by permafrost. The water will eventually force itself in an upward direction where it then freezes, resulting in the soil above it being pushed into a cone-shaped mound.

Thermokarst – This is the name given to very irregular surfaces of a mixture of hollows and hummocks. Small domes form on the surface during the winter period as a result of frost-heave action. As the summer approaches, the ice thaws which then causes these domes to collapse which create small depressions on the surface. However, some ice lenses may grow and create larger hummocks which may last for more than one year and may even become covered with vegetation. Even though they may last for more than a year they will eventually collapse during a summer thawing period. This process of thawing and freezing creates this uneven surface.

Thermokarst in Yakutsk

Patterned ground – This is the name given to distinct, and often geometric shapes, which are formed by ground material. These are created by the continuous process of freezing and thawing of groundwater which pushes stones towards the surface as smaller soils flow and eventually settle under these stones. Over time, this freezing and thawing process sorts out the material to eventually create patterned ground.

There are several types of patterned ground:

            Circles:  sorted sediments with finer material in the middle and larger material on the outside creating a circle shape.

Circle type patterned ground in Svalbard

            Polygons: These form as water freezes and expands, pushing apart the grains of soil in the active layer.  This then creates small cracks. Water then fills these cracks and the process of freezing and thawing occur which wedge the crack open. As the freezing and thawing continues, the wedges become bigger and so a polygon pattern is created.

Polygonal patterned ground

            Steps: These generally develop from circle and polygonal patterned ground. It is usually a terrace-like feature with a border of vegetation or large stones and contains both sorted and unsorted material.

            Stripes:  These are lines of stones, vegetation and soil and can consist of either sorted or unsorted material.

Stone stripe

Palsa – These are low mounds which contain permanently frozen ice lenses. They are usually 1-7 meters in height and may be 15-50 meters in length. They are formed from groundwater and often occur in groups.

A group of palsas from a birds eye view

As with glacial landforms, I think it is important that pupils are able to have a visual aid when learning these periglacial landforms. At the end of the lesson, to help cement what has just been learnt, a sheet with glacial and periglacial landform pictures could be handed out and pupils have to determine what the landform is and whether it occurs in a glacial or a periglacial environment.

Links used:

http://www.physicalgeography.net/fundamentals/10ag.html

http://ngm.nationalgeographic.com/geopedia/Permafrost

http://www.slideshare.net/pdxmas/periglacial-processes-presentation

Periglacial processes

Now that I have outlined the key terms that I think were quite handy to know when talking about periglacial environments, I am now going to move onto periglacial processes.

One of the main periglacial processes is mass movement. This is due to the periglacial environment: the thawing and freezing of water throughout the year which leads to water lying above the permafrost, low temperatures meaning that water cannot evaporate and a lack of vegetation so the soil cannot properly hold the soil together. However, this mass movement term is very broad and it can be narrowed down to a more specific process:

Solifluction – This is the slow, downslope movement of saturated soil and sediment. As the ice thaws into water, it cannot infiltrate the hard ground below it and so begins to move on the surface, typically downslope moving material with it. This process can be seen as it can create lobes which are semi-mixed surface deposits.

The diagram above shows the process of solifluction

The diagram above shows the process of solifluction as well as showing the lobes that can be created with a visual example of these forms.

Frost heave – this is the upward and outward movement of the ground surface which is caused by the formation of ice within the soil. Ice crystals develop in the winter when the active layer of the permafrost freezes and these expand upwards at the soil surface. Stones which are in the soil cool down much quicker than the surrounding soil and so ice forms here much faster. As this water freezes it expands and pushes the stone upwards. This process continues until the stone eventually reaches the surface. Soil and stones that are pushed up in this manner eventually form small domes and the stones located on top of these domes will eventually move down slope via processes of mass movement.

Nivation – This is a process that occurs underneath patches of snow, in hollows of rock. Frost action that occurs beneath the snow (mainly cycles of freeze-thaw weathering) gradually wears away and eventually shatters this underlying rock. In the spring when thawing takes place, mass movement carries away these deposits of weathered rock. Periodic freeze-thaw weathering causes the creation of nivation hollows.

Frost shattering – This occurs as a result of continuous cycles of freeze-thaw weathering and the wet conditions of the active layer. Water enters into cracks and joints in the rock and as the temperature drops, the water freezes causing it to expand and therefore puts pressure on the rock, weakening it. When the ice thaws, it contracts. This continuous process will eventually weaken the rock to the point that it shatters.

Aeolian processes – Due to the lack of vegetation in periglacial environments, the soil is more prone to wind action. This can produce a loess (for example in northern China).

I found it difficult to find diagrams of each of these processes. However, when teaching them it might be good to get the students to draw their own diagrams of each of these processes. This would aid in their learning by not only writing down the processes but by drawing them and so it might help with remembering them. It could also be turned into some form of game; putting up my own diagrams of the different processes around the room and getting students to move around the room and guessing which processes go with which diagram. Then afterwards, getting them to sit down and volunteer what they thought each process was and why. This would help to engage the students and might also help quieter students as they would have had a chance to discuss with others and so may help give them more confidence with volunteering answers in a class discussion.

In my next post I will look at the different periglacial landforms that may be created as a result of these different processes.

Links used:

http://www.slideshare.net/pdxmas/periglacial-processes-presentation - slides on periglacial processes

http://www.physicalgeography.net/fundamentals/10ag.html

http://www.discover.ltd.uk/downloads/examples/UnitF761ColdEnvironments_2009.pdf

http://coolgeography.co.uk/A-level/AQA/Year%2012/Cold%20environs/Periglaciation/Periglacial%20processes.htm

Key terms and definitions

With my previous topic of glaciers, I created a table of key words and definitions and I feel that this really helped me to get to grips with the subject as it helped to know what key words to look out for! I am therefore going to do the same with periglacial environments.

Active layer	The uppermost ground layer which thaws in the summer and freezes in the winter
Alpine permafrost	Found at much higher elevations
Continuous permafrost	Underlies nearly all of the landscape (except maybe rivers and deep lakes which don’t freeze through to the bottom)
Discontinuous permafrost	Zones of permafrost which have numerous scattered thawed areas
Freeze-thaw weathering	Water enters cracks or joints in rocks. When temperatures drop it then freezes, causing the water to expand which puts pressure on the rock. When temperatures rise the water contracts. This repeated process causes the rock to weaken and eventually shatter into many angular pieces
Frost creep	Slow, downslope movement of materials because of frost heaving and thawing and is influence by gravity
Frost heave	The upward or outward movement of the ground surface which occurs as a result of formation of ice in the soil
Gelifluction	Slow, downslope flow of unfrozen materials on frozen ground (permafrost). Form of solifluction
Ground Ice	All types of ice that is contained both in freezing and frozen ground
Ice lenses	Horizontal layers of segregated ice
Ice Wedge	Downward, narrowing ice masses. Can be between 2 and 3 metres wide at their base and can extend into the ground up to 10 metres
Needle Ice	Groups of narrow slivers of ice that form in more moist soils when temperatures drop below freezing at night
Palsas	Low mounds of permafrost with cores of segregated ice and peat
Patterned ground	Distinct, symmetrical geometric shapes which are formed by ground material
Permafrost	Frozen ground that stays at or below 0°C for two or more years
Pingos	Mounds of earth covered ice
Pore Ice	Ice that develops in the pores of soil and rocks where water can accumulate and then freeze
Sand Wedge	In more arid, cold environments, ice wedges may accumulate sand blown in by the wind within winter cracks.
Segregated Ice	Masses of almost pure ice that grow within permafrost
Solifluction	The slow, downslope flow of sediment and soil which is saturated with water
Sporadic permafrost	Small scattered areas of permafrost found in generally unfrozen areas
Talik	Permanently unfrozen ground in regions of permafrost
Talik (closed)	Unfrozen ground that is encased within permafrost
Talik (open)	Unfrozen ground that is open to the surface
Talik (through)	Unfrozen ground that is exposed to the ground surface as well as to a larger mass of unfrozen ground beneath it

As with the glacier definition table, it would be good to give students this at the start of the topic so that they have it for reference. At the end, as a fun sort of test they could cut the tables up into key terms and definitions and have to match them together. When learning these terms it would be good to show the students pictures as it is good for the students to be able to apply what they are learning to real life landscapes.

An introduction to periglacial environments

Having made a lot of progress with my learning of glaciers I am now going to move on to looking at periglacial environments, including processes and landforms.

To begin with, it is important to know exactly what periglacial means. Looking at a variety of websites:

A periglacial environment originally referred to areas bordering glacial areas, but has now been extended to refer to those areas with a tundra climate. This includes mountainous areas in the mid-latitude regions or where frost processes and permafrost occurs. This definition includes approximately 20% of the earth’s surface.

Periglacial environments can be found on the edges of polar or glacial environments, for examples areas of Siberia, Greenland and Canada. It is also important to include that periglacial environments usually have a seasonal temperature variation with mean summer temperatures usually rising above 0°C for a certain period.

Now that we have a definition of periglacial environments, it is important to look at the key words within the definition.

Permafrost

Permafrost is ground that remains frozen that stays at or below 0°C for two or more years and occurs in areas where the mean annual temperature is colder than 0°C. It is not solely found in cold landscapes, but can also be found in low latitude regions with areas of high elevation. This is known as alpine or mountain permafrost and can be found in the Rocky Mountains and the Andes. This kind of permafrost can occur at elevations as low as 8,000 feet.

The thickness of permafrost is dependant on a variety of variables: snow cover, vegetation cover, the temperature of the air near the ground, bodies of water and the heat from the interior of the Earth. The active layer of permafrost is the uppermost ground layer which thaws in the summer and freezes in the winter. When vegetation is present, it is restricted solely to this layer as roots cannot break through the frozen ground below.

The map above shows the extent of permafrost on a global level. Showing the map to students would be good to not only illustrate the extent of permafrost but to help with global locational knowledge (e.g. mountain ranges shown on the map)

There can be two types of permafrost:

Continuous – Regions with severe winters and temperatures below freezing leading to permafrost underlying nearly all of the landscape (except rivers and deep lakes which don’t freeze to the bottom). The thickness of the active layer varies in accordance with the temperature – in colder areas, permafrost is topped with an active layer of less than a foot thick.

Discontinuous – Warmer regions where the mean annual air temperature is only slightly below 0°C and local variables determine whether permafrost is either formed or maintained. Discontinuous permafrost can be further split into two subdivisions:

            Extensive discontinuous – occurs in with mean annual temperatures ranging between –2°C and -4°C.

            Sporadic – occurs in areas with mean annual temperatures ranging between 0°C and -2°C.

Permafrost is often found in peatland areas as whether or not it forms is dependant on how well the surface is insulated from the soil and rock which lies below it. Peat has many properties which make permafrost formation possible. Dry peat is a brilliant thermal insulator and so in the summer it prevents the heat from reaching the ground. On the other hand, when peat is wet or frozen it is an efficient transmitter of heat from the ground into the atmosphere. Thus, discontinuous permafrost can be found in peatlands throughout North America, Europe and Asia.

The picture above is a good map to show permafrost extent in the Northern Hemisphere as well as the different types of permafrost that can exist within a variety of places. 

This introduction to periglacial environments is a necessary start to begin to look at the key terms. When teaching this, it would be good to show student the map so that is would be easier for them to remember the parts of the world where permafrost occur. With regards to the different types of permafrost, showing them pictures and asking them what type they think it would be will engage them with the topic and may be better than simply getting them to read a text book or copy off the board.

Links used:

http://ngm.nationalgeographic.com/geopedia/Permafrost - National Geographic

http://www.slideshare.net/rgamesby/11-periglaciation-areas - Types of permafrost

http://fds.oup.com/www.oup.com/pdf/oxed/Pages%20from%20aqa_as_ch02.pdf - Permafrost map

http://www.hazardz.co.uk/131GED/periglacial.pdf - Map of permafrost in Northern hemisphere

Glaciers and Climate Change

The last section of glaciers that I am going to look at is that of climate change. I think it is important to look at this as it is a topic that is nearly always on the news and is something that everybody hears a lot about today. Although it is a dynamic topic, I think it is good to look at it in context with glaciers as when people talk about climate change it is often how the world’s glaciers will respond and in turn, how it will impact on sea levels.

Climate Change

Firstly, it is important to define what exactly climate change is. To begin with, it is essential to note that when people talk about climate change they are talking about anthropogenic climate change – that caused by humans. This occurs as a result of the release of greenhouse gases in the atmosphere which trap heat which enters Earth (the enhanced greenhouse gas effect). Climate change refers to any process that may cause an adjustment to the climatic system. This phrase is often better to use than ‘global warming’ as climate change can have many other effects than solely warming.

Glaciers and climate change

Shrinking glaciers

The video above begins to illustrate what is happening when people talk about climate change having an effect on glaciers. They are very sensitive to temperature fluctuations and so it is very easy to see the effect that an increase in temperature can have on a global scale since the beginning of the twentieth century, glaciers around the world have begun to rapidly recede, with few exceptions. This occurs as a result of an increase in temperature which then leads to an increase in glacial melt and also causes calving. Both of these two processes lead to a glacier receding.

The Columbia glacier, Alaska

One of the most renowned glaciers that has been affected by climate change is the Columbia glacier in Alaska. One of the fastest moving glaciers in the world, over the past 25 years it is estimated that it has receded by 15km. The video linked above is very good for illustrating the extent of how much the glacier has receded over this time period – very beneficial for putting the facts into a more comprehensible visual aid.

Chacaltaya Glacier 

Located in Bolivia, the Chacaltaya glacier was hugely relied upon by people living near the glacier in two main cities; both for water and for tourism. This glacier was once the world’s highest ski run and people from around the world would visit the glacier every year. However, in 2009 the glacier disappeared completely bringing economic fears and those of water issues. Nearly 80 million people rely on Andean glaciers as a source of water and electricity (Hydro-electric Power) and with temperatures rising as they currently are, there are many people at risk.

The image shows how far the glacier had receded from 1940 to 2007. However, in 2009 the glacier had completely disappeared.

Karakoram Glaciers

Glaciers located in the Himalaya Mountains; in particular those flowing in the Karakoram mountain range on the border of China and Pakistan, have actually been growing over the past decade, despite the global pattern of glaciers receding and is due to an increase in snowfall to the region.

Looking at a range of different websites and text books, it is clear that the global general pattern of movement is that of glaciers receding. Although there are some exceptions (mainly those in the Karakoram region) the increasing average temperature of the Earth is resulting in the melting of glacial ice which is contributing to a rise in sea levels. This section could be taught as a round up of the glacier topic with students using the knowledge that they have gained from learning about glaciers and putting it all together to look at the effect of climate change on them (for example, using key words such as calving and ablation) as well as using their locational knowledge to find the glaciers that are receding and those that are growing.

Links used:

http://www.bbc.co.uk/science/earth/water_and_ice/glacier#p00gbg92 – Glacier video

http://nsidc.org/cryosphere/glaciers/questions/climate.html - National Snow and Ice Data Centre

http://www.extremeicesurvey.org/index.php/education_toc/glaciers_and_global_warming - Extreme Ice Survey

http://education.nationalgeographic.com/education/encyclopedia/glacier/?ar_a=1#page=3 – National Geographic

http://www.bbc.co.uk/climate/impact/glaciers.shtml - BBC

http://www.guardian.co.uk/environment/2010/dec/21/what-is-climate-change The Guardian

http://news.bbc.co.uk/1/hi/8046540.stm#image – BBC, Bolivian glacier

http://www.guardian.co.uk/environment/2012/apr/15/karakoram-glaciers-grown-research - The Guardian, Karakoram glaciers