AVALANCHES
Shear stress must exceed the sheer strength of a mass of snow which is located on a slope in order for an avalanche to occur. Sheer strength is associated with its density and temperature, but snow avalanches usually result from two very different types of snow pack failure:
Most avalanches start off with a gliding motion, then rapidly accelerate (particularly on steep slopes in excess of 30°). Three types of flow occur: powder, dry flow, wet flow.
Although they usually follow similar tracks, they are still extremely hazardous and kill approximately 200 people per year. Most of these deaths are in the Alps/Rockies.
MINI CASE STUDY EXAMPLE:
Italian avalanche – January 2017
But by Thursday afternoon authorities held out little hope of finding anyone left alive after an avalanche buried the four-storey building with its eight staff and 20 guests, including several children, inside.
They were reported to have assembled on the ground floor on Wednesday awaiting an evacuation after a series of earthquakes had rocked the area during the day, but it was delayed because of the bad weather. Then the avalanche hit.
Amid treacherous weather conditions, rescue workers and sniffer dogs continued their search on Thursday at the four-star Rigopiano hotel in the lower Gran Sasso mountain range of the central Abruzzo region.
Titti Postiglione, head of the department’s emergency office, said more avalanches were possible because the temperature was rising, while further quakes were also possible. “This is an enormously complex rescue operation,” she said.
LAHARS
Some of the most destructive volcanic hazard events are caused by lahars (also known as volcanic mudflows or debris flows). This relates to glaciated landscapes because sometimes the volcanic region is glaciated and consequently when the volcano erupts, the heat melts glacial ice and consequently a lahar is formed.
The problem with this is that, around the world, there are many locations where, despite several historic lahar events, population density has increased and consequently so has infrastructure. This means that there are more people at risk of death and injury.
MINI CASE STUDY EXAMPLE:
Mount Rainier – USA (Washington)
One of the greatest hazards from Mount Rainier is from lahars, also known as volcanic mudflows or debris flows. Areas inundated by past lahars are densely populated and contain important infrastructure such as highways, bridges, ports and pipelines.
Mount Rainier is particularly susceptible to lahars because ice, loose volcanic rock and surface water are abundant, and because some slopes have been weakened by hydrothermal alteration of rocks which now contain lots of water and slippery clay.
Lahars look and behave like flowing concrete and they destroy or bury most manmade structures. Past lahars at Mount Rainier have travelled 40-50 miles per hour and were as much as 150 metres deep. Summer and autumn are seasons when lahars are most common because glaciers produce large amount of meltwater and intense rains fall on land with very little snow cover.
GLACIAL OUTBURST FLOODS
Also known by the Icelandic term jökulhlaup. It is a powerful flood caused by the sudden release of a subglacial or ice moraine dammed lake. There is potential for an outburst flood whenever meltwater collects behind a moraine, but the sudden catastrophic release can occur because of several things:
· Overflow and melting of an ice dam (common now climates are warming)
· Breakdown of an ice dam because of tectonic activity
· Irreversible overtopping of a moraine dam by large tsunami-style waves triggered by an avalanche or landslide into the lake
· Failure of moraine dam by melting of ice within it
· Enlargement of pre-existing tunnels beneath the dam because of pressure
Glacial outburst floods are a huge threat because they can destroy property tens or even hundreds of km from their source, especially in areas where people have settled for many years e.g. Andes, European Alps & Himalayas.
MINI CASE STUDY EXAMPLE:
The case of Nepal
In its history, Nepal has experienced several glacial outburst floods originating from numerous glacial lakes (some of which have even come from outside its territory). They are widely feared due to their serious devastation, even though the area experiences regular earthquake tremors and wildfires.
Among the identified ‘critical’ lakes is the Tsho Rolpa Lake. It is the largest moraine-dammed lake in the Himalayas and is fed by the Tradkarding glacier. The glacier is retreating at a rate of over 20 metres and, in some years within the last decade, sometimes even 100 metres a year.
The lake has grown six fold due to the melting glacier and this poses a high risk to people who live downstream as the amount of water released would be about 30 million cubic metres, affecting about 10,000 lives, thousands of livestock, agricultural land, bridges and other infrastructure. There is also a large HEP project located about 80km below the lake itself.
LEISURE AND TOURISM
Tourism in glaciated landscapes is often cited as an example of one of the biggest threats. Over the centuries, travel to glaciated landscapes has become romanticised and it now represents an expensive leisure activity suitable for all, with the only real barrier being cost. During the Victorian era, Arctic travel was only for the wealthy, whereas today, Antarctica represents the journey of a lifetime as it is often deemed as being the last remaining great wilderness (approx. 40,000 tourists per year now visit the Antarctic).
But why are people so ‘obsessed’ with glaciated landscapes? Well…
MINI CASE STUDY EXAMPLE:
Pressure on the Swiss Alps
Atop industry in the Alps, tourismis alsoa major driver of urbanisation. Large tourist resorts have an area consumption rate that is far greater than that of a non-tourist community. In addition, touristic areas also experience an increase in motor traffic. This is especially problematic for remote and sensitive Alpine regions which would otherwise be safe from urban sprawl.
Now, modern adventure sports (mountain-biking, canyoning, or paragliding) and some motor-based leisure activities areentering areas previously untouched by tourism. This iscausing major disturbances to wildlife in the Alps and poses very direct threats to biodiversity.
One of the most ecologically devastating forms of leisure activities in the Alps is winter ski tourism.There are currently about 300 ski areas throughout the Alps where 10,000 transport facilities serve more than 3,400 km² of ski areas. The construction of ski runs causes irreparable damage to the landscape. The increasing use of snow canons sets off additional problems by their use of water, energy, and chemical and biological additives.
URBANISATION
MINI CASE STUDY EXAMPLE COMBINED:
European Alps
The expansion of urbanised centres is threatening the very last natural relics in Alpine lowland areas. Many Alpine valleys have already lost most of their biodiversity value due to urban sprawl.
Humans first settled in elevated areas of the most accessible alpine valleys which offered the best conditions for housing and farming. These settlements eventually grew and slowly spread to the side valleys.Valleys of the easily reachable Rhone, Rhine, Inn, and Adige rivers have already lost most of their biodiversity value.
Natural habitats in the valley bottoms-riverbeds, floodplain forests, wetlands, alpine steppes - have been destroyed by expanding settlements. The transport infrastructure associated with this urban sprawl is a major barrier for many species in the Alps,preventing the establishment of ecological networks.
Now, the Alpshave reached anew level of urbanisation. The average living space occupied by a person has doubled since 1950. Even with minor population growth, there has been a sharp rise in the number of residential properties.
The continual expansion of cities, towns, villages, and hamletsarenow threateningeven the more remote areas.
While the majority of Alpine communities lie below 1000 m, some cities, mostly tourist centres, are situated at higher altitudes. Holiday homes are being built almost everywhere. Apartment complexes or residential tourist buildings are significantly contributing to the rising level of urbanisation.
AVALANCHES
Shear stress must exceed the sheer strength of a mass of snow which is located on a slope in order for an avalanche to occur. Sheer strength is associated with its density and temperature, but snow avalanches usually result from two very different types of snow pack failure:
Most avalanches start off with a gliding motion, then rapidly accelerate (particularly on steep slopes in excess of 30°). Three types of flow occur: powder, dry flow, wet flow.
Although they usually follow similar tracks, they are still extremely hazardous and kill approximately 200 people per year. Most of these deaths are in the Alps/Rockies.
MINI CASE STUDY EXAMPLE:
Italian avalanche – January 2017
But by Thursday afternoon authorities held out little hope of finding anyone left alive after an avalanche buried the four-storey building with its eight staff and 20 guests, including several children, inside.
They were reported to have assembled on the ground floor on Wednesday awaiting an evacuation after a series of earthquakes had rocked the area during the day, but it was delayed because of the bad weather. Then the avalanche hit.
Amid treacherous weather conditions, rescue workers and sniffer dogs continued their search on Thursday at the four-star Rigopiano hotel in the lower Gran Sasso mountain range of the central Abruzzo region.
Titti Postiglione, head of the department’s emergency office, said more avalanches were possible because the temperature was rising, while further quakes were also possible. “This is an enormously complex rescue operation,” she said.
LAHARS
Some of the most destructive volcanic hazard events are caused by lahars (also known as volcanic mudflows or debris flows). This relates to glaciated landscapes because sometimes the volcanic region is glaciated and consequently when the volcano erupts, the heat melts glacial ice and consequently a lahar is formed.
The problem with this is that, around the world, there are many locations where, despite several historic lahar events, population density has increased and consequently so has infrastructure. This means that there are more people at risk of death and injury.
MINI CASE STUDY EXAMPLE:
Mount Rainier – USA (Washington)
One of the greatest hazards from Mount Rainier is from lahars, also known as volcanic mudflows or debris flows. Areas inundated by past lahars are densely populated and contain important infrastructure such as highways, bridges, ports and pipelines.
Mount Rainier is particularly susceptible to lahars because ice, loose volcanic rock and surface water are abundant, and because some slopes have been weakened by hydrothermal alteration of rocks which now contain lots of water and slippery clay.
Lahars look and behave like flowing concrete and they destroy or bury most manmade structures. Past lahars at Mount Rainier have travelled 40-50 miles per hour and were as much as 150 metres deep. Summer and autumn are seasons when lahars are most common because glaciers produce large amount of meltwater and intense rains fall on land with very little snow cover.
GLACIAL OUTBURST FLOODS
Also known by the Icelandic term jökulhlaup. It is a powerful flood caused by the sudden release of a subglacial or ice moraine dammed lake. There is potential for an outburst flood whenever meltwater collects behind a moraine, but the sudden catastrophic release can occur because of several things:
· Overflow and melting of an ice dam (common now climates are warming)
· Breakdown of an ice dam because of tectonic activity
· Irreversible overtopping of a moraine dam by large tsunami-style waves triggered by an avalanche or landslide into the lake
· Failure of moraine dam by melting of ice within it
· Enlargement of pre-existing tunnels beneath the dam because of pressure
Glacial outburst floods are a huge threat because they can destroy property tens or even hundreds of km from their source, especially in areas where people have settled for many years e.g. Andes, European Alps & Himalayas.
MINI CASE STUDY EXAMPLE:
The case of Nepal
In its history, Nepal has experienced several glacial outburst floods originating from numerous glacial lakes (some of which have even come from outside its territory). They are widely feared due to their serious devastation, even though the area experiences regular earthquake tremors and wildfires.
Among the identified ‘critical’ lakes is the Tsho Rolpa Lake. It is the largest moraine-dammed lake in the Himalayas and is fed by the Tradkarding glacier. The glacier is retreating at a rate of over 20 metres and, in some years within the last decade, sometimes even 100 metres a year.
The lake has grown six fold due to the melting glacier and this poses a high risk to people who live downstream as the amount of water released would be about 30 million cubic metres, affecting about 10,000 lives, thousands of livestock, agricultural land, bridges and other infrastructure. There is also a large HEP project located about 80km below the lake itself.
LEISURE AND TOURISM
Tourism in glaciated landscapes is often cited as an example of one of the biggest threats. Over the centuries, travel to glaciated landscapes has become romanticised and it now represents an expensive leisure activity suitable for all, with the only real barrier being cost. During the Victorian era, Arctic travel was only for the wealthy, whereas today, Antarctica represents the journey of a lifetime as it is often deemed as being the last remaining great wilderness (approx. 40,000 tourists per year now visit the Antarctic).
But why are people so ‘obsessed’ with glaciated landscapes? Well…