GLOFs and Glacio-Volcanism Revision

How have glacial lakes evolved?

The Little Ice Age established moraine complexes that enclose Himalayan glaciers in dams; land patterns also see down wasting occur and supraglacial debris thicken towards the snout to form and add to terminal moraines; behind these dams glacial lakes form fed by glacier melt and precipitation

What is the process chain that triggers GLOFs?

There is a cascading chain of processes leading to GLODs where rock or ice falls, extreme precipitation or upstream floods can generate waves and increase lake levels to overtop dams and begin erosion; the dam breach wider and depends quickly due to hydraulic forces leading to irreversible damage and rapid emptying of the lake

What are the three dam types and how do they differ in stability and drainage?

Bedrock-dammed, moraine-dammed and ice-dammed; bedrock are the most stable and fail via overtopping, moraine-dammed are more unstable and can fail through overtopping, direct failure and erosion; ice-dammed are the most unstable and water can escape through channels and the subglacial drainage system

What are the direct impacts of GLOFs, where is vulnerability highest to these impacts?

Primary impacts include loss of life and infrastructure due to very high discharge, they can cause valley erosion and channel modification with the most vulnerable areas in areas of scattered housing, reliance on agricultural land, river banks and hikers travelling along trails in flood plains; risks increase as populations and tourism pressures increase in highly exposed areas

How does individual perception influence GLOF hazards?

Perceptions can influence individual responses and actions; rapid onset hazards including flash flooding are ranked as higher risk that gradually compounding ones; those who are younger, rely on tourism for income or who have prior experience of a GLOF are also likely to perceive a higher risk

What are the indirect impacts of GLOFs?

Glacial ice can contain chemicals such as lead and pesticides or pathogens; therefore, flood water is likely to be contaminated and poses a risk to human health and agriculture when incorporated into drinking water and irrigation; there are also interactions with water supplies and hydropower plants

What are the climatic and glacial characteristics of the Sagarmatha National Park?

It is situated in NE Nepal in the Asian monsoon zone and the majority of glaciers are debris covered which complicates exchanges between the ice and the atmosphere

How have glaciers changed since the 1960s?

Glaciers have been retreating since the 1960s leading to the formation and expansion of new glacial lakes since the 1990s to create new hotspots for GLOFs

How should cryospheric risks such as GLOFs be managed?

They should be considered in a holistic manner to inform hazard donation maps and management plans involving sustainable partnerships with scientists, policymakers and local communities

What is glacio-volcanism?

Volcanic eruptions beneath continental ice sheets or within glacierised basins

How are risks from glacio-volcanism formed?

They can be isolated volcanic or cryospheric hazards, as well as those formed from glacio-volcanic interactions

What is the main driver of the ice-volcano interaction and how does this influence volcanic eruptions?

The interaction is fuelled by the presence of water supplied by glacier and snow melt during an eruption leading to more energetic explosions and larger volumes of fine ash produced

What are the terms for the interactions that lead to more energetic explosions?

Phreatomagmatic fragmentation and fuel-coolant interactions

Why and how has interest in glacio-volcanism increased?

Since the massive tephra production of the 2010 Eyjafjallajokul research has expanded into glacio-volcanism seeing an increase in technology such as remote sensing allowing for improved monitoring of eruptions; the influence of climate change on glacier thinning and retreat now forms a new inquiry into the nature and associated risk of glacio-volcanism

How many people live within 30km of a glacierised volcano?

7 million

What are lava flows and what are their impacts?

Volcanic hazards that have the potential to melt snow and ice as ejected lava flows over the surface of glaciated volcanic basins; this has the potential to create huge volumes of meltwater and cause floods

Where and when were lava flows evidenced?

At the 2010 eruption of Eyjafjallajokul in Iceland much lava was produced and travelled beneath and within the glacier; this led to the enlargement of subglacial tunnels due to the heat and eventually roofs collapsed and channels were forced accommodating lava flows across the surface of the glacier

What are pyroclastic density currents and what are their impacts?

Gravity driven flows of tephra, rock fragments and high temperature fluidised gases travelling very fast in a disruptive manner driven by the explosive expansion of trapped steam and fuel-coolant interactions leading to rapid fragmentation of magma; this can also form meltwater for lahars and flooding

Where and when were pyroclastic density currents evidenced?

At the 1980 eruption of Mount St. Helens in Washington low density currents were formed on the day of the eruption

What area did the pyroclastic density flows of Mount St Helens 1980 cover, and where was this concentrated?

15.5 km², mostly North of the volcano

What are jokulhlaups and what are their impacts?

The rapid and sudden drainage of lakes or bursts of meltwater driven by geothermal heating that can cause extensive flooding and transport sediments over long distances; these can be caused by lava flows, PDCs or long term release of volcanic heat into snow or ice filled craters

What are lahars and what are their impacts?

Water flows rich with volcanic debris formed as flood water mixes with volcanic debris and entrains surface deposits to have devastating impacts on local populations and infrastructures especially in remote areas

When and where were lahars evidenced?

1985 Nevado del Ruiz eruption in Colombia

What percentage of the ice cap of Nevado del Ruiz was melted by pyroclastic flows?

10%

What as the impact of two combined lahars on the east flank of the volcano?

The combination of two lahars led to the complete inundation of Armero at around 11pm killing most of the population in waves of the lahar

What as the impact of lahars on the west flank of the volcano?

Over 1000 people were killed in the town of Chinchina

Where else were the impacts of lahars evidenced and how did this occur?

Mount St Helens 1980 where lahars began within minutes of the eruption principally driven by the melting of debris laden ice and snow by hot tephra

Where were the most voluminous flows in this eruption located?

North Fork Toutle River

Why are ash clouds from glacio-volcanic eruptions important to study?

Glacio-volcanic eruptions tend to produce higher volumes of fine ash that is able to travel long distances within the atmosphere

Where was the most famous example of a glacio-volcanic ash cloud evidenced?

Eyjafjallajokul 2010 eruption

How much fine ash made up the ash cloud?

70 Teragrams

What percentage of the tephra fell in Iceland, where was the rest dispersed?

50%, the remainder was carried South East to Europe and the North Atlantic

Over what area was tephra detected in Europe and the North Atlantic?

7 million km²

What were the impacts of this ash cloud?

Global financial losses of $5 billion, closure of European and transatlantic air space and airpots, contaminated water sources, river blockages and tourists stranded in Iceland

What is the long term effect of ash clouds, what does this form?

The ejection of ash and aerosols into the atmosphere following a volcanic eruption lead to short term cooling due to the blocking of sunlight but this is offset by a long term warming as a result of GHG emissions contributing to positive feedback loops where glaciers continue to thin and eruption rates continue to increase due to differences in lithostatic pressure

How has monitoring of glacio-volcanism developed?

Global spatial databases attempt to identify where land ice and volcanoes co-exist to predict future hazard potential, behaviours and inform reduction and mitigation strategies

What has the application of risk based databases to Colombia showed?

There remains considerable hazard potential from volcanoes including Nevado del Tolima, Huila and Ruiz where large volumes of ice retain the conditions for an event comparable to the 1985 lahars

What has the application of risk based databases to Chilean and Argentinian Andes showed?

Global climate change is leading to a decline in glacier area and an associated increase in glacio-volcanism and lahars