Geography - COLD ENVIRONMENTS
How might how cold environments be managed in the future?
- Increased protection - there are growing demands for cold environments to be protected from development and human activity. E.g. in 2015, the president of the USA proposed extending the wilderness area of Alaska, which would prevent oil exploration in that area. - Decreased protection - as global population increases and reserves of oil and minerals in other areas are depleted, development of cold environments may become more of a priority than conservation. Areas that are currently protected (e.g. Antarctica) may be opened up for exploitation.
How do the conditions of the tundra make plant growth difficult?
- Low levels of insolation means that there's a short growing season (50-60 days). - Low precipitation levels - soil moisture is frozen for much of the year. - Soils are often waterlogged as thawed water is unable to penetrate to depth because of the permafrost and the fact that evaporation levels are low.
What is the vegetation of the tundra like?
- Low productivity - Very few plant species - low biological diversity - Absence of full grown trees - tundra = treeless plain in Sami. Are dwarf varieties - Most of the flowering plants are perennials. Have hardy seeds armoured by a thick seed case. - 5 types of plants, each occupying own specialised niche: lichens, mosses, grasses, cushion plants and low shrubs. Lichens are pioneer plants - they colonise bare areas. They have no roots and are able to absorb water and nutrients directly into their foliage. Together with mosses they initiate soil formation.
Name the main landforms formed in periglacial landscapes
- Patterned ground - Ice wedges - Pingos - Solifluction lobes - Teracettes - Thermokarst
Name the landforms that are mainly produced by glacial erosion
Corries Aretes Pyramidal peaks Roche mountonée Glacial troughs, including hanging valleys and truncated spurs
What is till?
Unsorted material (rocks, clay and sand) that has been deposited directly by the ice. Mainly transported as supra-glacial or en-glacial debris, and deposited when the ice melted. Individual stones tend to be angular to sub-angular, unlike river or beach material which is rounded and smooth. Reflects the character of the rocks over which the ice has passed.
What are the current, predicted and now occurring and predicted for the future impacts of climate change on cold environments?
Current: 1. SHRINKING GLACIERS - Globally 90% of glaciers are losing ice mass - Millions of people rely on glacial meltwater as their freshwater supply - Glaciers respond to local climate, so some glaciers in some regions do advance at certain times 2. PERMAFROST MELTING - e.g. in Alaska. - A 6º temp. increase in the Antarctic by 2100 would lead to a 30-85% loss of near-surface permafrost. This can cause buildings to collapse and ice roads (essential supply routes to remote settlements) to be used for less time before they begin to thaw each year. 3. CHANGING MIGRATION PATTERNS of some species - E.g. caribou, are changing due to changes in the seasons. - bird watchers in Britain are spotting changing patterns in the migration of certain bird species that over-winter there. Predicted and now occurring: 1. LOSS OF SEA ICE - a small area of the Arctic Ocean has ice cover all year. It is at its smallest in September. Studies have predicted it is shrinking, and with the use of remotely sensed images showed that 2012 was the smallest on record. - Arctic ice is also becoming thinner making it more vulnerable to enhanced rates of melting in the future. 2. ACCELERATED SEA LEVEL RISE - studies show sea level rise for most of the 20th Century was about 1.7 mm/year. - satellite monitoring then showed mean global sea levels rose by about 3mm/year between 1993 and 2009. - in 2013 the IPCC report said the current average rate is around 3.2mm/year. (thermal expansion and the addition of meltwater contributing to increase). Predicted for future: 1. FURTHER SEA LEVEL RISE - due to the shrinking of the Greenland ice sheet. The ice sheet is expected to almost completely melt by 2100, contributing to the projected sea level rise by 2100 of between 18 and 59 cm above 1990s levels. - this could flood low-lying coastal cold environments. 2. PF TO THAW TO INCREASING DEPTHS - a 6ºC temp. increase in the Arctic by 2100 would lead to a 30-85% loss of near-surface PF. - this could trigger a positive feedback (known as the permafrost carbon feedback), as methane (a greenhouse gas) that is trapped in the PF is released. More methane in the atmosphere will cause temperatures to rise, which will cause further melting of permafrost and the release of even more methane. 3. POSSIBLE GROWTH OF ANTARCTIC ICE SHEET - warmer temps. could increase the amount of precipitation (snowfall). - other theories suggest that the extent of the ice sheet may be increasing due to acceleration of glacial movement to the sea. 4. FURTHER TEMP. INCREASES - average global temps. could rise between 1.4-5.8ºC by 2100. - latitudes between 40ºN and 70ºN could rise between 5 and 8ºC by 2100, due to the loss of sea ice and snow cover reducing albedo rates. 5. INVADING SPECIES - increased issues of invasive species in warmer tundra environments - this could increase extinction rates of indigenous species that are outcompeted for resources - local populations' traditional way of life may be affected.
What are the processes of mass movement that occur in periglacial landscapes?
- Solifluction - occurs when summer temps. rise enough to melt huge amounts of water held as ice in the upper layers of the PF. Due to the impermeable layer of still frozen ground below, this water cannot drain away, and the little evaporation due to the cold temps. means that the surface layer becomes very wet. Excessive lubrication from this water reduces the friction between the soil particles. On slopes as gentle at 2º, this saturated layer becomes quite mobile and the soil begins to move downslope. The downslope movement of saturated soils can happen in many environments, but when related to the freezing and thawing of the active layer it is also referred to as gelifluction. - Congelifluction refers to any flows of earth within the still PF. - Frost creep - the gradual downslope movement of individual soil particles due to the alternating freeze-thaw cycles within the active layer. Water in soil expands when it freezes. This expansion causes soil particles to be forced upwards at right angles to the slope. When the ground thaws, the soil particles move vertically downwards - as a result they end up further down the slope. - Rock falls result from freeze-thaw action (frost shattering) and can involve the movement of large amounts of material. Scree slopes at the foot of slopes resulting from frost shattering are a common feature of periglacial landscapes. On relatively flat areas, extensive spreads of angular boulders are left, which are known as block field or Felsenmeer (sea of rocks).
Cold environments are fragile because of the harsh climate:
- The short growing season (when there is enough light and warmth for plants to grow) means that plants don't have much time to recover if they're damaged. - Slow rate of plant growth means that repairing damage can take a long time. - Plants and animals are adapted to the cold conditions, so they find it hard to adapt if the environment changes. - Decay is slow so pollutants are broken down very slowly (and remain in the environment for a long time). e.g. some say it could take over 50 years for an area of tundra to return to its former state after interference.
What are the two main processes of glacial erosion?
1. Abrasion = scraping and scouring of material the glacier is carrying on the valley floor and sides. Coarser, harder material may leave scratches in rock known as striations. Finer debris smoothes and polishes rock surfaces. The debris involved in abrasion is worn down by this process into very fine material known as rock flour. This rock flour is taken away from the glacier by sub-glacial meltwater streams, turning them a milky colour. 2. Plucking = involves the glacier freezing onto and into rock outcrops. Plucking mainly occurs at the base of the glacier where pressure and friction often result in the melting of ice. There is a considerable amount of meltwater at the base of meltwater at the base of most glaciers, which is very close to freezing point, and often this will refreeze, attaching the glacier to the bedrock. As the ice moves forward it pulls the bedrock away, leaving a jagged landscape. Common in well-jointed rocks and those where the surface has been weakened by freeze-thaw action (frost shattering). Plucking leaves a very jagged landscape.
What are the 3 categories of PF?
1. Continuous PF - found in the coldest regions, reaching deep into surface layers. In the very coldest areas, there is hardly any melting of the uppermost layer. In Siberia today it is estimated that the PF can reach down over 1,500km. 2. Discontinuous PF - occurs in slightly warmer regions, where the ground is not frozen to such great depths. On average, the frozen layer will extend 20-30m below the ground surface, although it can reach 45m. The are also gaps in the PF under rivers, lakes and near the sea. 3. Sporadic PF - found where mean annual temps. are around or just below freezing point. In these places, PF occurs only in isolated spots where the local climate is cold enough to prevent complete thawing of the soil during the summer.
Name the four main types of cold environment
1. Glacial 2. Polar 3. Periglacial 4. Alpine
What are the types of glacial deposit?
1. Lodgement till - sub-glacial material that was deposited by the actively moving glacier. Typical feature formed in this manner = drumlin 2. Ablation till - produced at the snout where the ice melts. Terminal, push and recessional moraines are typical features produced from ablation till.
Describe the formation of glacial ice from snow
1. Low temps result in precipitation falling as snow 2. This snow has an open feathery structure so air is trapped between the flakes and the snow has a low density - density of snow is approx. 50-300 kg/m3 3. Over time more snow will fall so the underlying layers will be compressed and the air will be expelled 4. If these compressed layers of snow manage to survive one winter's freeze and one summer's melt they will start to form firn (or Neve). 5. Firn/neve has a density of approx. 500 kg/m3 so still contains some air passages. 6. During the summer months meltwater may move through these air passages 7. When winter and therefore low temperatures return, this meltwater will freeze and help to create a denser mass. 8. Frozen meltwater and further compaction by subsequent years of snowfall helps change the firn into solid (glacial) ice - this is a process known as diagenesis 9. Diagenesis usually takes at least 30 years but can take up to 1000 years in polar climates where there is an absence of meltwater. 10. Solid ice has a density of approx. 900 kg/m3 and has a blue appearance due to lack of air (white indicates presence of air). 11. Once solid ice is formed, it may flow downhill in the form of a valley glacier A glacier is a flowing stream of ice.
What are examples of these activities that are exploiting fragile cold environments?
1. Oil extraction - oil spills can occur during transport of oil from this area, e.g. in 1989 there was a huge oil spill off the coast of Alaska when the Exxon Valdez oil tanker crashed. Over 40 million litres of oil spilled into the ocean, and over 250 000 birds and fish were killed. - oil spills can occur if pipelines leak. Between 1977 and 1994, on average there were 40 spills a year from the Trans-Alaska pipeline which runs the length of Alaska. Some of these were caused by intentional attacks and forest fires. 2. Fishing - can disrupt food chains, e.g. large-scale krill fishing in the Southern Ocean is depleting food supplies for whales and penguins. - overfishing of a species can severely deplete its population, sometimes beyond recovery. Overfishing of the Patagonian Toothfish in the Antarctic is currently a concern. - bottom fishing catches fish by dragging nets along the sea-bed. This disrupts the ecosystem (by reducing light levels through increased turbidity) and catches other species as well as the target one. It's carried out in the Gulf of Alaska, the Greenland sea and the Barents Sea. 3. Tourism - large cruise ships increase pollution in the area (from the ships and the tourists). - tourists and tourism developments (e.g. roads, hotels) disrupt wildlife and habitats, leading to reduced biodiversity 4. Hydroelectric power - hydroelectric dams can block the normal migratory path of fish. This can prevent them reaching spawning grounds, and so cause the fish population to decrease. Fish can travel long distances to spawn, so this can affect fish populations over a large area. - hydroelectric dams also heat up the water, which can endanger fish that are adapted to colder temperatures. 5. Mining - mining can lead to ground and surface water contamination, either by chemicals used during mining or by releasing the materials being mined into the environment. E.g. a lead-zinc mine in Maarmorilik (Greenland) was closed in 1990 but levels of lead and zinc pollution are still high in nearby fjords. - mining produces both solid waste and wastewater that has to be disposed of. Some mines don't have the facilities required to deal with the quantities of waste produced, so the waste is released into the environment, polluting the local area. Any human development may require additional infrastructure to be built, e.g. support buildings and access roads. These can cause more damage to the environment, and improved access may open the area up to further development.
What are the various management strategies currently in place to protect cold environments?
1. Protected areas - some countries have protected their cold environments by passing laws to prevent activities within them, e.g. some areas of Alaska are designated wilderness areas, where development is forbidden and access is limited. 2. International treaties - some cold environments are internationally important, and there are global management strategies to protect them in the form of treaties signed by countries around the world. E.g. the Antarctic Treaty - 1959 Now has 53 signatories. It states that Antarctica must only be used for peaceful purposes, including science. International cooperation between scientists is promoted. Military and nuclear activity is banned. 3. Monitoring and regulation - exploitation (e.g. the number of visitors) can be monitored to assess its impacts. Activities can be strictly managed, e.g. visitors to Antarctica have to clean and disinfect footwear when they land to prevent the introduction of non-native species. 4. Fishing quotas - in some areas the number of fish caught is limited, e.g. in the Barents Sea.
Glacial deposition landforms What are moraines, what are the features of moraine and how are they formed?
= Lines or a series of mounds of material, mainly running across glacial valleys. TERMINAL MORAINE The main type of moraine is terminal or end moraine - this is found at the point where the snout of the glacier has reached its furthest extent 'downstream'. Features: - Elongated at right angles to the direction of ice advance - Often steep-sided, particularly the side that the ice contacted - Can reach up to 50-60m high - Often crescent shaped, moulded to the form of the snout - Formed from unsorted ablation material (till). Formation: formed when ice melts during a period of snout standstill, when it has reached its furthest point down the valley and the material being carried is deposited. This is why they contain a range of unsorted material, from clay to boulders. RECESSIONAL MORAINE As glacier retreats it is possible for a series of moraines to be formed along the length of the valley, marking points where the retreat paused for some time. PUSH MORAINE If climate could for some time leading to glacial advance, a previously deposited moraine may be shunted forward up into a mound (push moraine). Recognised by the orientation of individual pieces of rock, which may have been pushed upward from their previous horizontal position. LATERAL MORAINE Deposited at the sides of the glacier MEDIAL MORAINE Deposited in the centre of the valley where two glaciers converge (the 2 lateral moraines joined together).
Explain what a corrie is, how it is formed. Give an example
= an armchair-shaped rock hollow with a steep back wall, and an over deepened basin with a rock lip. They often contain a small lake (tarn). Usually found on the north side of a mountain in the NH, where lower levels of insolation allow the increased accumulation of snow. 1. Nivation acts upon a shallow, pre-glacial hollow and enlarges it into an embryo corrie. This can be a slow process across several glacial periods within an ice age. 2. As the hollow grows the snow becomes deeper and is increasingly compressed to form firn and then ice. 3. Frost shattering takes place due to temperature variations. This creates loose material which falls onto the glacier. 4. The glacier reaches critical depth, so starts to move down slope. It pulls away from the back wall, taking material with it (plucking). This makes the back wall steeper. 5. As the glacier moves away from the back wall, a Bergschrund crevasse is created. Material from the valley side will use this to fall beneath the glacier, and this material is then used for abrasion. 6. Beneath the glacier there are various processes taking place, including nivation, abrasion and rotational flow. The result of these processes is the initial hollow becoming deeper and wider - this is helped by meltwater created by pressure melting. 7. As the hollow becomes deeper, the thinner ice at its edge does not produce the same amount of downcutting and a rock lip develops on the edge of the hollow. This rock lip can increase in height by the deposition of moraines formed when the glacier's snout was last in that position. 8. In a post-glacial landscape the corrie becomes a tarn with a steep back wall and a rock lip, creating a basin. EXAMPLE = Red Tarn in Lake District - depth = 25m, back wall rising 300m.
What is a pyramidal peak, how is it formed and what is an example?
A pointed mountain peak with at least 3 sides. If more than two corries develop on a mountain, the remaining central mass will survive as a pyramidal peak (their back walls). Has a very sharp appearance due to frost shattering. E.g. the Matterhorn in the Alps bordering Switzerland and Italy.
What is nivation?
A series of processes that operate underneath patches of snow in hollows, particularly on north- and east-facing slopes (in the NH). Most common in periglacial areas where temperatures fluctuate above and below freezing. Freeze-thaw action together with chemical weathering processes, operating under the snow, causes the underlying rock to disintegrate. As some of the snow melts in the spring, the weathered particles are 'flushed-out' of the hollow and moved downslope by the meltwater and solifluction. The accumulation of more debris by repeated debris by repeated seasons of freezing and thawing, and the accumulation of more snow leads to the formation of nivation hollows leads to the formation of nivation hollows which, when enlarged, can be the beginnings of a corrie.
Describe alpine environments - location - climate - soil - vegetation
Cold areas of land at an altitude above the treeline (the limit of an area where trees can grow - above this it's too cold). The Himalayas, the Rockies, the Andes. May include areas of glacial conditions at higher altitudes and periglacial conditions at lower altitudes. Older mountain ranges have lower relief and features of their well-developed glaciated landscapes have often been softened and smoothed by subsequent weathering and erosion. Climate - winters are cold (often below -10ºC) but summers can be mild (sometimes above 20ºC at lower latitudes). Temperatures decrease as altitude increases. Snowfall can be high. Soil - when ice melts in summer, soil is exposed in some areas. Higher up, land is permanently covered in snow and ice but lower down periglacial soils are present. Vegetation - the seasonally exposed soil means that plants can grow, e.g. grasses and alpine flowers.
What are the factors that cause the climates of the polar and tundra environments?
AHCKLOC - a hippopotamus can kick lots of conkers Altitude - height above sea/ground level. Temperature decreases by 1ºC for every 100m in altitude. Alpine environments near the equator must have a high altitude to ensure they have the low temperatures to sustain that environment. High albedo - rays are reflected off the snow because it is white, meaning that they are not absorbed by the ground and so they do not heat up the ground. This reduces the amount of heat that can contribute to the warming of the atmosphere. Cold air - this means that no evaporation can take place and so air doesn't hold as much moisture - little precipitation can fall. Katabatic winds - cold air flows downwards and it picks up speed whilst doing this as there it nothing stopping it (little vegetation). It flows along the valley floor. This increases the wind chill, which decreases temperatures. Low levels of insolation - the angle that the sun's rays hit these areas means that they cover a very large area. As a result, the suns energy is spread over a wide area and isn't as intense. In addition, the longer passage through the atmosphere allows for increased absorption, scattering and reflection of radiation. Less insolation therefore reaches the surface. Ocean currents - Antarctica is cold because the ocean currents circulate from the east to the west. This water is very cold because it is a long way away from the equator. It acts as a barrier from the warmer water near the equator. Ocean currents surrounding the Arctic run from north to south. The northwards current (the Gulf Stream) carries warm water from the equator to the Arctic, and the southwards current carries cold water from the Arctic back to the equator - this heats the Arctic up slightly. Continentality - cold environments that are close to the coastline are slightly warmer than ones in the middle of a continent - coastal areas gain heat energy from the sea.
How can glaciers be classified? What are the different types?
According to the temperature of their base. Warm-based glaciers (temperate) Found in milder areas, e.g. western coastal mountain ranges of N America. Tend to be smaller valley glaciers, typically ranging from hundreds of m's to a few km's in width, and hundreds of m's to tens of km's in length. Found in places with high winter snowfall rates and temperatures in spring and summer high enough to create rapid summer melt rates. Meltwater moves down through glacier and acts as lubricant, allowing the glacier to be far more mobile than cold glaciers. This faster rate of movement means that warm-based glaciers are more likely to erode, transport and deposit material. At the surface of the glacier there is a thin layer ( a few m's) of snow and fern subject to seasonal temp fluctuations, meaning that it melts at around 0ºC in the summer melting. This surface layer insulates the layers of ice beneath it. With increasing depth in a glacier the ice is under increasing pressure from the surrounding ice, which has the effect of lowering the melting point of the ice - this is known as pressure melting point. All ice in a temperate glacier is at or near the melting point because of the warmer atmospheric temps, the weight of the ice above and as temperate glaciers may be relatively thin, a greater proportion of the ice is influenced by geothermal heat at the bed. Main way they move = basal sliding Cold-based glaciers (polar) Generally found in places with low precipitation rates, even arid conditions, so receive little snowfall each year and accumulation rates are low. There is little or no melting of ice and so the ice can be very old, with the ice at the base of some Arctic and Antarctic ice sheets dating back around 100,000 years BP. All ice, except most upper surface layers that can be exposed to summer atmospheric temperatures of above 0ºC, is below the melting point. There is little meltwater associated with these glaciers as atmospheric and sub-glacial (geothermal) heat sources are not great enough to reach melting point. Other than limited melting of the surface in summer, the majority of ice loss is due to sublimation and the calving of icebergs/blocks. Movement in cold-based glaciers is much slower than in temperate glaciers as they are often frozen to their beds, thus most movement is due to internal flow. Much less erosion, transportation and deposition takes place.
What are glacial troughs, how are they formed, what are their main features and associated landforms?
Also called U-shaped valleys. Steep-sided valleys with flat bottoms. Formed by the erosion of a V-shaped river valley by a glacier. As the glacier erodes this valley it makes it deeper and wider. The action of glacial ice combined with huge amounts of meltwater and sub-glacial debris has a far greater erosive power than the pre-glacial river in the occupied valley. Main features: - Generally straight with wide base and steep sides - U-shape - Stepped, long profile with alternating steps and rock basins - Some glacial valleys end abruptly at their heads in a steep wall, known as a trough end, above which lie a number of corries. - Rock basins filled with ribbon lakes, e.g. Wast water in the Lake District. - Over-deepening below the present sea level. This leads to the formation of fjords when sea levels rose after the ice ages and submerged the lower parts of glacial valleys Associated landforms: - Hanging valleys on the side of the main valley - formed by tributary glaciers. They erode the valley floor much less deeply because are smaller than main glaciers (they contain much less ice). When these tributary glaciers melt, they are left at a much higher level than the glacial trough formed by the main glacier. E.g. the valley of Church Beck which flows down into Coniston Water in the Lake District Waterfalls fall from the hanging valleys into the main glacial trough. - Truncated spurs - formed when ridges of land (spurs) stick out into main valley and are chopped off (truncated) as the main valley glacier moves past. - Roche mountonée - small mounds of resistant rock on the valley floor. The upstream (stoss) side is smooth because it was smoothed by abrasion as the glacier moved over it. This abrasion also creates striations on the surface of the rock. The downstream (lee) side is steep and jagged where the glacier has plucked at it. They are relatively small features (up to a few tens of m's long and less than 5m high) (diagram on next page). After ice retreat, many glacial troughs were filled with shallow lakes which were later infilled. Post-glacial frost shattering modifies sides, developing scree which alters the original U-shape.
What is an arête, how it is formed and what is an example?
An arête is a narrow, steep-sided ridge. It is formed when two corries lie back to back or alongside each other. If enlarged over may glaciations, this steep-sided ridge is formed between the two hollows. E.g. Striding Edge above Red Tarn in the Lake District.
What are ice wedges?
Another feature that creates a type of patterned ground. Relatively narrow cracks or fissures in the upper layers of the ground filled with ice (sometimes extending below the level of permafrost). Due to the presence of air bubbles in the ice, the wedge has a milky appearance. They begin as small cracks, less than 5cm across, but over hundreds of years they can reach over 10m wide and extend many m's into the ground. Result from ground contraction due to extreme cold, generally in areas of continuous PF. During the winter the freezing of the soil in the active layer causes the soil to contract. In the following summer, the initial small crack is filled with meltwater (called an ice vein when it freezes). This process happens repeatedly through the cycle of winter and summer widening and deepening the crack to eventually form the ice wedge. The way the ground contracts creates a pattern of cracks on the surface, which when viewed from above, have a similar shape to stone polygons. These are therefore known as ice-wedge polygons. They are generally larger than stone polygons (15-30m in diameter) but can reach 100m across. These are also generally only found on flat or very gently sloping surfaces. If the climate warms enough for all the ice to melt it may be replaced by fined grained sediment that infills the void forming an ice-wedge cast.
Discuss polar environments: - location - differences between polar Arctic region and southern polar region - climate - soil - vegetation
Approx. 66º N and S of the equator Much of Arctic polar environment made up of the northern land areas of Asia, N America and Europe. The land-based polar environments can include glacial environments, e.g. the Greenland ice sheet and periglacial environments, e.g. northern Russia. In Arctic polar, the sea ice averages 3m in thickness and doubles in extent in Winter. Southern polar region - the ice sheet and surrounding ice shelves of Antarctica which cover 13 million km2, and the periodically frozen expanse of the Southern Ocean. Strong westerly winds, coldness of the ocean and the large landmass give Antarctic a colder climate than Arctic. The cold waters of S Ocean mean sea ice develops rapidly in winter from 2 million km2 in Feb to around 16 million km2 in September. The fluctuations in sea ice are much less in the Arctic due to the influence of surrounding continents. A difference between poles is that in winter sea ice around the Arctic is increasing while that of the north is shrinking. climate - very cold - mean monthly temps below freezing all year, winters normally below -40ºC and can reach -90ºC. Precipitation is low (no more than 150 mm/year), with all of it falling as snow (at the S Pole, precipitation is around 50 mm/year). Clearly defined seasons - cold summers and even colder winters. Strong winds blowing outwards from the centre of the continent. Winds over 200 km/hr recorded - substantial wind-chill factor. Winds also whip up the powdery snow to create frequent blizzards and white-outs. Soil - much of ground covered in ice. When soil exposed it is thin and nutrient poor and normally layer of permafrost (permanently frozen ground) beneath the soil. Vegetation - very few plants - some lichens and mosses on rocks and a few grasses in warmer areas, e.g. on the coast of Antarctica and in some parts of the Arctic.
What are the features of tundra soils?
Developed under tundra areas: - a lack of clearly defined soil horizons (layers) - a thin surface organic layer which is often very acidic - a uniform blue grey colour - waterlogged in summer - gleyed - because of the waterlogging, iron compounds are reduced to their ferrous form which is grey - as opposed to ferric compounds which are red-brown Surface litter is restricted by the limited tundra vegetation. The slow rate of decay of the vegetation due to the climate and the presence of only a few soil organisms means there are limited amounts of organic matter in the soil. Soil organisms normally act as mixing agents and as there are few available to carry out this work, the soils horizons are poorly differentiated. The freezing of the soil in autumn leads to it being churned and the horizons become further distorted. Where the soil overlies bedrock, frost-heave raises fragments to the surface giving rise to typical periglacial features.
Name the glacial depositional landforms
Drumlins Erratics Moraines Till plains
Fluvioglacial landforms Erosion Pro-glacial lakes and overflow channels - what are they and what are examples?
During deglaciation, lakes develop on the edges of ice, some occupying large areas. Overflows from these lakes which cross the lowest points of watersheds will create new valleys. When the ice damming these meltwater lakes totally melts, many of the new valleys are left dry, as drainage patterns revert to the pre-glacial stage. In certain cases, the postglacial drainage adopts them, giving rise to new drainage patterns. The River Thames was thought to have followed a much more northerly course before the Quaternary glaciation - its modern course was formed when ice filled the northern part of its basin and forced it to erode a different route. The River Severn believed to have been diverted during the last glaciation: Stage 1 (pre-glacial) - the RS flowed northwards to enter the Irish Sea in what is now the estuary of the River Dee. The present Lower Severn was a shorter river flowing from the Welsh borderlands to the Bristol Channel. Stage 2 (the last Ice Age) - ice coming down from the north blocked the River Severn valley to the north. The water from the blocked river formed a huge pro-glacial lake known as Lake Lapworth. The lake eventually overflowed the watershed to the south to join the original Lower Severn. In the process it cut through a solid rock area, creating the gorge at Ironbridge. Stage 3 (deglaciation and the post-glacial period) - as the ice retreated to the north the way should have been left open for the two rivers to return to the pre-glacial situation. However, the route north was blocked with glacial deposits, and as the Ironbridge Gorge has been cut very deep, the new drainage adopted this rather than its former route. The River Severn now flows from central Wales to the Bristol Channel.
What is a fragile environment?
Environments that are easy to damage and which take a long time to recover from damage.
Fluvioglacial landforms Deposition What features are formed by fluvioglacial deposition?
Eskers, kames, outwash plains and varves. Material transported by traction, saltation, solution and suspension.
Fluvioglacial landforms Deposition Eskers - what are their main features and how are they formed?
Features: - long ridges of material running in the direction of ice advance - have a sinuous (winding) form, 5-20m high - consist of sorted coarse material, usually coarse sands and gravel. - often stratified (layered) Formation: Eskers are believed to be deposits made by sub-glacial streams. The channel of the stream will be restricted by ice walls, so there is considerable hydrostatic pressure which enables a large load to be carried and also allows the stream to flow uphill for short distances - this accounts for the fact that some eskers run up gentle gradients. The load builds up the bed of the channel above the surrounding land, or close to the snout of the glacier the hydrostatic pressure may drop leading to an overburdening of the channel and deposition. Beaded esker - when the ridge of an esker is combined with mounds of material, possibly kames. Esker's are common in formerly glaciated areas of Europe and North America.
Fluvioglacial landforms Deposition Outwash plains (sandurs)
Found in front of a glacier's snout and are deposited by the meltwater streams that emerge from the snout of the ice. They consist of material that was brought down by the glacier and then picked up, sorted and dropped by running water beyond the position of the ice front. The coarser material travels the shortest distance and is therefore found near the glacier. The fine material, such as clay, is carried some distance across the plain before being deposited. Deposits are also layered vertically, which reflects the seasonal flow of meltwater streams. Meltwater streams that cross the outwash plain are braided - this happens as the channels become choked with coarse material because of the marked seasonal variations in discharge.
What are the locations of the different types of cold environment?
Glacial - can be found in polar and alpine settings Polar - 66º N + S of equator. Arctic - 10º C July isotherm (areas above this line have an average temp below 10º in July - the hottest month). South Pole - 10º C January isotherm (hottest month in S hemisphere). Periglacial - found at high latitudes, e.g. northern parts of N. America, Asia and Europe. Also at high altitudes, e.g. conditions exist around ice masses in mountain ranges. Alpine - found at high altitudes at any latitude.
Discuss the features of glacial environments - what they are - what's found there with examples - climate - soil and vegetation
Glaciers exist on every continent except Australia. = areas of land that are PERMANENTLY covered in ice. At present, 10% of land on Earth is permanently covered by ice. Land can be covered by glaciers or ice sheets: - Glaciers = masses of ice that flow downhill. Two types: 1. valley glaciers - fill valleys and can be several km long, e.g. Franz Josef glacier in New Zealand. 2. Corrie glaciers - small glaciers found in bowl-shaped hollows high up in mountains, e.g. Red Tarn in the Lake District - depth = 25m, back wall rising 300m. - Ice sheets = domes of ice covering huge areas of land, e.g. Antarctic ice sheet - covers about 98% of the Antarctic continent. Climate - temperatures permanently cold enough for ice to be present all year round. May be warm enough in summer for meltwater to affect glaciers. Most have high snowfall - in extremely cold areas, e.g. parts of Antarctica, ice sheets and glaciers persist even if snowfall is low. Soil and vegetation - because they're covered in ice permanently there is no exposed soil. As a result, very few plants are found here, although algae and moss may grow on the glacier surface during summer.
What is the glacial system (inputs, stores, flows and outputs)?
Inputs: - Snow (from precipitation or avalanches) - Condensation of water vapour from the air which then freezes - Bits of rock collected when the glacier carves away at the landscape, and rocks that have fallen onto the glacier from above, e.g. by freeze-thaw weathering Stores: - Main store = ice - Meltwater stored on and within glacier, e.g. supraglacial lakes on top of glacier. - Rocks stored on or in glacier Flows: - Meltwater flows through glaciers, e.g. from stores in supraglacial lakes to channel storage at base of glacier - Debris flows through glaciers, e.g. from surface storage to landforms Outputs: - Meltwater - Surface snow melting and evaporating - Sublimation - ice turning straight into gas without going through liquid stage - Snow can be blown away by strong winds - In glaciers that end at sea or lake, blocks of ice fall from snout of glacier into water, creating icebergs (the calving of ice blocks or icebergs). When inputs = outputs, the system is said to be in a state of dynamic equilibrium.
Fluvioglacial landforms Deposition Varves
Lakes on the fringe of the ice are filled with deposits that show distinct layering. A layer of silt on top of a layer of sand represents one year's deposition in the lake and is known as a varve. The coarser, lighter coloured layer represents spring and summer deposition where meltwater is at its peak and the meltwater streams are carrying their maximum load. The thinner, darker coloured layer is made up of silt that settles during autumn and through the winter as the meltwater stream discharge decreases and the very fine sediment in lakes settles to the bottom. Varves are good indicators of the age of lake sediments and of past climates as the thickness of each varve indicates warmer and colder periods. Also, any organic material caught in them can be used for paleoclimatic research.
What happened during the Pleistocene?
Lasted from 2.5 million years ago to 11,700 years ago. During this time there were fluctuations in global temperature which led to colder glacials (when glaciers advanced and sea levels fell) and warmer interglacials (when glaciers retreated and sea levels rose). The last glacial maximum (ice sheets at their largest size) was 21,000 years ago. Polar ice sheets covered much of the UK, and most of S Europe was periglacial. CURRENTLY, we are in an interglacial - glaciers are retreating.
Discuss periglacial environments - location - climate - soil - vegetation
Located on the margins of glacial and polar environments ('peri' for periphery). Generally found in dry high-latitude areas that are not permanently covered by ice, but are cold enough for periglacial processes to occur (temp. frequently or constantly below freezing). Northern Alaska, N Scandinavia, Siberia. Climate: - cold and precipitation is fairly low - 380 mm or less (mainly in the summer). - clearly defined seasons - brief, mild summers and long, cold winters. Soil: - thin, acidic and not very fertile. Normally a permafrost layer topped with a layer of soil that melts in the summer (active layer). Vegetation: - due to low precipitation, cold temps and often think poor soils, vegetation is sparse. - plants grow slowly and don't grow very tall. - Grasses are the most common plants. Some small, short trees grow in warmer, sheltered areas. - Nearer the poles only mosses and lichens can survive. Some areas in lower latitudes but higher altitudes do experience periglacial conditions.
What are the different ways ice can move?
More melting around bits of rock protruding from the valley floor due to more pressure on the ice. Meltwater can refreeze downstream of the obstruction where there's less pressure, so the flow tends to be faster around obstruction and slower downstream. Basal sliding - occurs because as glacier moves over bedrock there is friction. Lower levels also under a great deal of pressure and this combined with friction results in some melting. Meltwater acts as lubricant, enabling ice to flow more rapidly - main way warm-based glaciers move. Rotational flow - occurs within corries. Ice moving downhill can pivot about a point, producing a rotational movement. This, combined with increased pressure within the rock hollow, leads to greater erosion and an over-deepening of the corrie floor. Internal deformation (including creep) - occurs where stress builds up within a glacier, allowing ice to behave with plasticity and flow. Common when obstacles are met. Involves the ice crystals orientating themselves in the direction of the glacier's movement and sliding past each other. This is the main flow of cold-based glaciers (polar) due to the lack of meltwater meaning that they tend to be frozen to their beds. Extensional flow = occurs when valley gradient becomes steeper - gravitational force pulls ice downwards. The ice accelerates and becomes thinner, leading to reduced erosion. Crevasses may be created on ice surface. Compressional flow - occurs where there is a reduction in the gradient of the valley floor, leading to deceleration and a thickening of the ice mass. At such points, ice erosion is at maximum.
Fluvioglacial landforms Deposition Kames
Mounds of fluvial-glacial material (sorted and often stratified coarse sands and gravel). Deposits left when meltwater flows into a lake dammed up in front of the glacial snout by recessional moraine deposits. When the ice retreats further, the kame often collapses. There is the suggestion that hollows on the surface of a melting glacier would fill up with sediment and then gradually go down to lower levels as the ice melted - ultimately forming a mound on the ground surface. Kame terraces are frequently found along the side of a glacial valley and are the deposits of meltwater streams flowing between the ice and the valley side. Meltwater streams deposit heaviest load first so kame terraces have gravel at bottom and finer material at top.
Describe 2 examples of the feedbacks that occur in the glacial system
Negative feedback - e.g. if size of input increases, glacier can speed up so more water and ice are output and the mass of the glacier remains the same. Positive feedback - e.g. ice has high albedo. If glaciers retreat, there is less ice and so less of the sun's energy is reflected and more is absorbed, so temperature of ice increases and glaciers retreat further.
Frost action/freeze-thaw cycles lead to frost shattering. What does this entail?
Occurs in areas where there's moisture and temperatures that fluctuate above and below freezing. Water from rainfall or melting enters the joints and crevasses in rocks + cliff faces. When temps drop below 0ºC, the water in cracks freezes and expands (by just under 10%), exerting pressure on the surrounding rock. Over time, repeated freeze-thaw action weakens the rocks and causes pieces to fall off. On steep slopes this leads to a collection of material at the base known as scree. In a glacial valley much of this material falls from the valley side onto the edges of the glacier (an input) and some finds its way to the base of the ice via numerous crevasses and moulins on the glacier's surface.
Periglacial landforms Thermokarst
Occurs when ice in the ground (e.g. pingos) melts, causing the ground to collapse and holes to form. The holes become filled with water, creating an uneven, marshy landscape. Only results from temperature changes (not erosion and weathering), meaning that features occur where human activity inadvertently warms the surface layers of PF.
Glacial deposition landforms What are till plains and how are they formed?
Often found behind a terminal moraine or towards the margins of former ice sheets in low-lying areas. They are wide areas of generally flat relief created by a till sheet. The underlying bedrock may be uneven but is hidden by a thick covering of glacial till, sand and gravel. The thickness varies - it is thicker where depressions exist in the underlying surface. The material tends to be quite compacted giving a poorly drained surface with bogs, lakes and slow-moving meandering streams. E.g. large till plains south of the Great Lakes in N America, marking the margins of earlier Laurentide ice sheets.
Fluvioglacial landforms Deposition Kettles
On the outwash plain there is often a series of small depressions filled with lakes or marshes, known as kettle holes. It is believed that they are formed when blocks of ice, washed onto the plain, melt and leave a gap in the sediments. The holes fill with water to form small lakes. Aquatic plants become established in the lakes + this leads over time to the development of a marshy area and then peat.
What is the tundra?
One of the most northerly ecosystems - 50º to 80ºN. Climate: - long and bitterly cold winters with temperatures averaging -20ºC. - brief, mild summers with temperatures rarely above 5ºC. - at least 8 months of the year when the temperature remains below 0ºC. - small amounts of precipitation, less than 300 mm/year, most of which falls as snow. - frequent strong winds which increases the wind chill.
Explain some of the problems and solutions facing plants in the tundra
P - limited moisture S - small waxy leaves - minimises transpiration P - low levels of insolation S - can photosynthesise at low temperatures, even under a thin covering of snow S - low albedo off plant surfaces - can absorb more radiation than surrounding surfaces P - strong winds S - ground hugging plants. Also lets them take advantage of warmth close to the ground P - lack of organic matter S - perennials, can store food from year to year P - frozen/waterlogged soil S - shallow roots - live off active layer
What is permafrost?
Permanently frozen ground. In areas where temps. below the ground surface remain below 0ºC continuously for more than two years, PF will occur. Currently it is estimated PF covers 20-25% of the Earth's land surface. If water is present in the soil a significant amount will freeze, cementing the mineral and organic particles together. The ground below this frozen layer that remains unfrozen is known as TALIK. When summer temps. rise above freezing, the surface layer thaws from the surface downwards to form an active layer - depth of this layer varies considerably and depends upon local conditions, but may extend up to 4m. As the ice in this layer melts, large volumes of water are released.
Periglacial landforms Pingos
Pingos are a conical hill with a core of ice. They can reach up to 70m high and 600m wide. They can survive for thousands of years. They grow only a few cm's per year. OPEN system Pingos Common in Greenland (Greenland type) Occur in areas of discontinuous permafrost where there are areas of permafrost (land frozen for at least 2 years) and talik. The active layer continually freezes and melts year on year above the permafrost and talik. Over winter, as the active layer freezes, water can become trapped between the descending freezing plane of the active layer and the permafrost that surrounds it. This promotes the growth of an ice lens which pushes the land up above it as it expands. Water underneath the permafrost can move through the talik between the permafrost areas because of capillary action and hydraulic pressure. This water migrates to the ice lens and freezes, swelling the ground above further. CLOSED system Pingos Found in areas of continuous PF where there is a lake at the surface. The lake insulates the ground so the area beneath remains unfrozen. When the lake dries up, the ground is no longer insulated and PF advances around the area of unfrozen land. This causes water to collect in the centre of the unfrozen ground. This water eventually freezes and creates a core of ice that pushes the ground above upwards. ------------------------------------------------ As the bingo grows, increasing cracks and instability of the steep sides may expose the ice inside. When the core has completely melted all that remains is a doughnut-shaped mound possibly containing a small lake in the centre. Some present-day temperate regions have fossil bingos evidencing their colder past climates.
Glacial deposition landforms What are erratics?
Rocks that have been picked up by a glacier or an ice sheet, carried along and dropped in an area of completely different geology. E.g. Norber erratics in the Yorkshire Dales.
Periglacial landforms Terracettes
Small periglacial features. Often referred to as 'sheep tracks' as they have the appearance of small narrow pathways running horizontally across the side of a slope. Form when vegetation interrupts soil moving down a slope due to frost creep or another mass movement process. This causes a flatter area to build up behind the obstruction, which leads to a series of step-like terraces. Some geographers believe they may have ben formed by the trampling of animals traversing steep slopes.
Fluvioglacial landforms Erosion Meltwater channels
Some of the main features of fluvioglacial erosion. Key features: - Supraglacial (top of glacier), marginal (sides of glacier), englacial (in middle of glacier), sub-marginal (bottom sides of glacier), subglacial (bottom of glacier). - Subglacial streams are able to flow uphill due to hydrostatic pressure - Only meltwater flowing in channels in contact with the bedrock floor leave any erosional trace in the post-glaciated landscape - It is believed that beneath glaciers 2 types of channels occur: 1. Nye channels - those cut downwards into bedrock by headward erosion 2. Röthlisberger channels - those that cut upwards into ice itself by meltwater. Only leave any postglacial trace if the channel becomes choked with sediment. - Believed that with high discharge and its turbulent flow, large meltwater channels can create sub-glacial valleys that are often deep and riddled with potholes.
What are the different types of debris?
Supra-glacial debris - material transported on surface of glacier En-glacial - material buried within the glacier Sub-glacial - material found at base - may include rock fragments that have fallen down crevasses as well as material eroded at base of glacier.
What is an example of an outwash plain and its associated features?
The Skeidarár Sandur in southern Iceland is a vast outwash plain from the Vatnajökull icecap. It covers 1,300 km2 and exhibits the classic features of fluvio-galcial landscapes, including: - deep accumulations of black gravel, sand and silt originating from the local volcanic rock - criss-crossed by constantly shifting braided streams - evidence of abandoned channels as the seasonally changing discharge levels affect rates of erosion and deposition. - very sparse vegetation and little evidence of human habitation. This results from the constant risk of floods or glacial bursts due to volcanic eruptions in this area. The last eruption under this glacier was in 1996. - close to the glacier snout are ridges or steps that may result from kames or kettle features.
Explain the glacial budget and how glacial and interglacial cycles affect it
The balance between accumulation (inputs) and ablation (outputs) over a year - it shows whether the mass of ice in a glacial system has increased or decreased. Sometimes called the "mass balance". The zone of accumulation = the upper part of the glacier where inputs > outputs and therefore, more mass is gained than is lost over a year. Zone of ablation = where outputs > inputs in the lower part of the glacier and mass is lost rather than gained. Boundary between zones = equilibrium line. If accumulation > ablation for over 1 year, glacier has a positive regime (positive mass balance) and grows + advances (glacial advance). If ablation > accumulation for 1 year, glacier has a negative regime (negative mass balance) and glacier shrinks + retreats (glacial retreat). If accumulation = ablation for 1 year, glacier stays same size and the position of the snout doesn't change - glacier is in dynamic equilibrium. Difference between acc and abl in one year is known as the net balance. During glacials, the climate begins to become colder and in winter more precipitation falls as snow. Summers begin to shorten, so there is less time for the snow to melt allowing it to remain year on year. Initially leads to permanent snow cover in upland areas (the lower edge of which is known as the snow line). As annual mean temperatures continue to drop, the snow line moves down the slope.
What is weathering?
The breakdown and/or decay of rock at or near the Earth's surface creating regolith that remains in situ until it is moved by later erosional processes. Can be mechanical, biological or chemical. The low temps in cold environments limit the impact of biological weathering, but mechanical and chemical weathering shape the environment and provide material for glacial erosion.
What is patterned ground?
The repeated cycles of freezing and thawing of the active layer can produce a range of landforms collectively referred to as patterned ground. Main process involved = frost heave Happens when water underneath stones freezes + expands, forcing stones upwards. Once they reach the surface, they roll down to the edge of the mounds tat have formed, so they form circles around them (polygons form when the mounds are close together). If the mounds are on a slope, the stones roll downhill and form lines. Also frost contraction causes the ground to crack into polygon shapes. The cracks get filled with stones, forming polygon patterns on the surface.
Glacial deposition landforms What are drumlins, what are their main features and how are they formed?
They are smooth, oval, half-egg shaped hills of till. Up to 1.5km in length and 50-60m in height. Upstream (stoss) side is steep and downstream (lee) side is gently sloping. Elongated in direction of ice advance. Often found in groups/swarms - given their shape often referred to as a 'basket of eggs topography', e.g. a well-known swarm at Hellifield in the Ribble Valley. Many are found in the LOWER end of glacial valleys. Formed from unsorted till, and most are believed to have little internal structure. Considerable debate about their formation. Theories include: 1. Ice moulds and shapes a pre-existing landscape of glacial drift (ground moraine) deposited in previous glacial advance. 2. The moving glacier deposits till around a nucleus formed by some unevenness in the floor, such as protruding rock or a mass of frozen till. This material is then moulded as ice continues to move over it. 3. (one of most widely held views) - drumlins result from ice being overloaded with debris. This reduces its capacity to carry material and deposition occurs at the base of the ice. This material is shaped by further glacial advance.
Periglacial landforms Solifluction lobes and sheets
When solifluction occurs on slopes of around 1-20º solifluction sheets are formed. These have a smooth surface and can extend over 100m across a slope. Where slopes have a steeper gradient of 10-20º then solifluction lobes will form. These have a tongue-like appearance that extends downslope and can be up to 50m wide and 5m high. Depending on the local subsurface conditions and slope processes solifluction terraces can also form.