Introduction | Mass Movements | Rockfall and Avalanches | Ice and snow avalanches | Landslide and debris flow | Case Study
What are glacial hazards?
Generally, there are two types of hazards found in glacial environments that can impact humans. First, we have direct hazards such as avalanches and rockfalls. Second, we have indirect hazards for instance glacier lake outburst floods (GLOFs) and water resource issues 1 (Figure 1).
Who is affected by glacial hazards?
Glacier recession in high mountains and polar environments can lead to destabilisation, leading to a number of glacial hazards such as glacier collapse, rock and ice avalanche, glacier lake outburst floods (GLOFS) and debris flows.
Some of these hazards can have impacts on people over a short time scale (minutes–days), e.g. ice/snow avalanches and glacial floods. Others can have an impact over much longer time scales (months–years–decades), e.g. water resource problems 1.
Why should we care?
As the climate warms and glacial environments change, hazards are becoming more frequent, thus impacting people more often. Given that, it is important we understand hazards in order to prepare for and mitigate against their impacts 2,3.
Mass movements as glacial hazards
The term ‘mass movement’ covers various geomorphological processes, but generally refers to the downslope movement of snow, ice, rock, and debris, often in combination 2.
Mass movement events are particularly common in mountainous regions due to the steep topography, unstable slopes, and an abundance of materials 5.
Generally, the most frequently observed mass movement events in glaciated regions are:
- Rock falls and avalanches
- Snow and ice avalanches
- Landslides and debris flows
Rockfalls and avalanches
Generally, rock avalanches are the result of bedrock slope failures. Here, large amounts of material break off intact rock and travel at high speeds downslope, breaking apart even further as they travel 6. As a result, huge deposits of material on the glacier surface (as can be seen in Figure 2).
Rock avalanches are not to be confused with rockfalls. A rockfall is simple the movement of already loose material thus are generally much smaller than rock avalanches 2.
Snow and ice avalanches
Generally avalanching is the most widely studied mass movement event 1 and has huge impacts in populated valleys across Scandinavia and Central Europe.
Snow and ice avalanches can begin in three ways (Figure 3), causing large volumes of material to be released downslope.
Not only can avalanches have direct impacts in the valleys below, they can also lead to secondary impacts if avalanches dam rivers or enter glacial lakes causing outburst 1.
FUN FACT: Mass movement events are the primary trigger for GLOFs worldwide.
Landslides and debris flows
Landslides and debris flows (made up of a water-debris mix, usually 50-70% sediment) generally originate from steep slopes, talus slopes, and fluvioglacial deposits 5.
As a result, they are most common in periglacial and paraglacial environments due to the abundance of loose materials 9,10.
Often triggered by precipitation 11 these types of mass movement can significantly transform the landscape, altering channel morphology, rerouting rivers, and forming lakes 3.
Case study: 2013 Garhwal Himalaya tragedy
In June 2013 in the Indian Himalaya two large debris flows travelled along the Mandakini River and its tributaries, resulting in widespread devastation reaching as far as 200km downstream (as can be seen in figure 4). Consequently, in the village of Kedarnath, more than 6000 people were killed, countless roads and bridges damaged or destroyed, 30 hydropower plants impacted, and more than 100,000 pilgrims and tourists were left stranded (Figure 4) 9. Half of a major pedestrian route up to Kedarnath was destroyed, which undoubtedly hindered the rescue of pilgrims and evacuation of local people.
