Threats Facing Glaciated Landscapes (Edexcel A Level Geography)

Threat of Natural Hazards

• Active and relict glacial landscapes are inherently dangerous: 

  • Avalanches

  • Rock falls

  • Debris slides

  • Flooding

• Increased populations, developments, and tourism put people at risk within these areas

Avalanches

• Avalanches are rapid movements of snow down a slope, and are common in mountainous areas

• Avalanches occur when shear stress exceeds the shear strength of a mass of snow on a slope, which is linked to the snow's density and temperature

• Two types of pack snow failure:

  • Loose snow - small amounts of snow move and roll down the slope

  • Slab avalanches - large 'slabs' of snow break away from underlying snow

    • This type of avalanche is the most dangerous 

    • A large, fully-developed avalanche can weigh up to a million tonnes

    • Created when higher temperatures are followed by a freeze, creating an 'ice crust' on the surface, which is unstable

• Avalanches start with a glide and then accelerate to speeds of 320km per hour (200m per hour), picking up even more snow as it rushes downhill

• Occur most frequently on slopes over 22°

• Also, occur on north-facing slopes where the lack of snow limits snow stability (doesn’t have time to bind with partial melting)

• Three types of avalanches are: 
  

  • New snow can fall off older snow (dry avalanche)

  • Or partially melted snow moves (wet avalanche)

  • Mostly from slab avalanches (powder avalanches)

    • A powder cloud forms with a large quantity of snow being suspended in the air

    • These are the most dangerous of avalanches 

• All avalanches are a significant hazard and kill approximately 200 people a year

Lahars

• A lahar is a large mud and debris flow as a result of volcanic activity

  • Nevado del Ruiz, Colombia is known locally as the ‘sleeping lion’ and has not erupted for nearly 150 years

  • In the early hours of November 13th, 1985 it erupted

  • A combination of seismic activity, glacial instability, and extreme temperatures all combined to form one of the deadliest mudflows in history

  • Occurred during the night when most of the 27000 residents of Armero in Tolima were asleep

  • Armero was virtually destroyed by the 3-8m of mud and rubble that swept onto it and killed an estimated 23,000 people

Glacial outburst floods (GOFs)

• Powerful floods caused by the sudden release of meltwater from a subglacial or ice moraine-dammed lake

• Can be trigged in six ways:

  • Overflow and melting of the ice dam

  • Breakdown of ice dam due to tectonic activity

  • Increased rise in water levels

  • Mass movement creating an overtopping of the moraine dam through displacement

  • Catastrophic failure of moraine dam by slow ice melt within the moraine

  • Increased water pressure enlarging pre-existing tunnels beneath the ice dam

• GOFs can be seasonal and dams can reform each year

• These outbursts are sudden and pose a threat to property and people around the world

• Meltwater can travel hundreds of kilometres from its sources and areas such as the Alps, Iceland, the Andes, and the Himalayas have a long history of GOFs

• Periglacial areas are also seeing increased ground subsidence due to ice melt and flooding, risking new areas to sudden flooding

Threat of Human Activity

• Glaciated landscapes face varying degrees of threat from human activities:

  • Urbanisation

  • Reservoir construction

  • Leisure and tourism

Urbanisation

• Vary from isolated farms to nucleated towns depending on the location

• Relict glaciated areas are traditionally agricultural with intermittent market towns

• The impact varies on accessibility, but with the growth of tourism and the general population, many of these areas have seen a rise in development, pollution, and damage/loss of flora and fauna habitats

• Infrastructure developments can damage permafrost and increase rates of melting through the release of greenhouse gases into the atmosphere

• The exploitation of resources and discovery of new areas have increased risks of pollution by toxic waste from the mining of gold, copper, or uranium 

• Oil and gas spills into the polar waters have damaged the fragile balance of oceanic ecosystems which cascades onto land-based ecosystems

Reservoir construction

• The construction of reservoirs in valleys is leading to landscape and hydrological changes

• Upland glacial landscapes provide natural features for HEP and reservoir building 

• Power from HEPs provides power to urban areas

• Reservoirs regulate water supplies

• However, they also dramatically alter the landscape and impact a river's regime

  • The River Ganges rises in the Himalayas and discharges in Bangladesh

  • The glacial waters provide for many people, animals, and plants along its course

  • With the increased planned and constructed HEPs along its course, the impact is far-reaching with decreased water supplies and sediment supplies to areas downstream that rely on the river for their existence

Tourism

• Places such as Antarctica have seen an increase in the number of tourists

• Approximately 100,000 tourists visit Antarctica each year, and large cruise ships increase pollution in the area - both from the ship and the tourists themselves 

• Seeds from non-native species, caught on tourist clothing, are being seen growing in the ice-free coastal areas, threatening the continent's biodiversity

• Adventure tourism to extreme cold environments is a growth industry for countries and local communities

• Developments such as roads and hotels, disrupt wildlife and damage habitats and migratory patterns, leading to reduced biodiversity

• In the European Alps, social mobility and wealth have increased the rate of deforestation for ski resorts and supporting infrastructure, leading to habitat loss and fragmentation

• Tourism increases demand for energy and water resources

• In Zemett, Switzerland, snow cannons add artificial snow to the slopes, but they are energy-intensive and add chemical and biological additives to the soil in the process

• Relict glaciated landscapes are also under threat from tourism

  • Trekking causes damage to fragile mountain ecosystems

  • Plant communities, such as tundra flower meadows, need just 25 people a week and damage begins

Degradation of Landscape by Human Activity

• Human activity can degrade the landscape and fragile ecology of glaciated landscapes through:

  • Soil erosion

  • Trampling

  • Landslides

  • Deforestation

Cold environments are fragile

• Natural development and processes within cold environments occur slowly 

• They are long-term carbon and methane stores with a high albedo of up to 90% reflection of insolation

• Any changes quickly cascade, and once damaged, it takes a long time for the ecosystem to recover, if at all

• Adaptations of flora and fauna occurred over a long period of time, in order to survive their harsh surroundings 

• Plants and animals have to cope with a lack of daylight, climatic variations, and a very short growing season

• Specialism, limited species numbers, sensitivity to changes, and slow development make this environment very fragile

Impacts

• Ecosystems are resilient, however, they all have a threshold of tolerance and once crossed, can tip the ecosystem into a spiral of decline

• Certain human activities have a bigger impact than others

• Mountain biking or horse trekking are more damaging than walking

• Deforestation and poor upland farming lead to soil erosion and landslides 

  • Soil erosion is a major issue in the Andes, through over-cultivation and overgrazing on the slopes, in the need to provide subsistence for its growing populations

• Exposed soils allow for weeds, resistant to erosion, to take over

• Leisure activities damage ecosystems through trampling and compaction

  • Small leaves and delicate stems are damaged

  • This reduces photosynthesis, growth, and biomass

  • This provides less water and nutrients to the ecosystem

  • Continued trampling compacts the soil leading to poor soil condition, bare soil, and greater erosion

  • People will avoid rutted and exposed soil but fail to realise that walking on other areas leads to further damage