4. Primary and secondary volcanic hazards

Describe tephra as a primary hazard giving reference to a case study and further impacts?

• Solid material of varying sizes that is ejected by a volcano – ranges from ash (less than 2 mm in diameter) to volcanic bombs (more than 64mm).

• Lapilli sized material (6-64mm) can be carried upward within a volcanic plume and downwind within a volcanic cloud but is dropped to the ground when the eruption cloud cools. Volcanic ash (ash fallout) (<2mm) can be carried within the plume for long distances

• Eg: Eyjafjallajokull 2010: airspace closed for a week, 10 million people left stranded, Kenyan farm workers laid off because fresh flowers and veg for European markets couldn’t be transported (disruption to trade blocs). Locally, it contaminated water sources, and thick deposits of ash made farming hard

Describe volcanic gas as a primary hazard giving reference to a case study and further impacts?

• Eruptions releasing large quantities of gases such as sulphur dioxide and carbon dioxide → respiratory issues

• Eg: Nyiragongo 2002 - released CO2 and sulfur dioxide → respiratory issues. Longer term risk in low-lying areas where gas can accumulate called “mazuku” → 10–30 people die each year

Describe pyroclastic flows/nuees ardentes as a primary hazard giving reference to a case study and further impacts?

• Very hot (800 degrees C), high velocity (80km per hr) made up of gas and tephra. They form when the eruption column collapses and the gas and tephra rush down the sides of the volcano

• Eg: Chances Peak, Montserrat 1995: Been dormant for over 300 years, flows covered the surrounding area and capital (Plymouth) causing many homes, hospitals etc to be destroyed. However, evacuation was successful and only 19 died.

• LIC - helped by international aid: British government provided a £41 million aid package, and British Navy evacuated 7,000 residents

Describe lava flows as a primary hazard giving reference to a case study and further impacts?

• Lava flows travel at different speeds depending on slope, temperature and viscosity

• Most move slowly so don’t kill people but can cause significant damage to property and infrastructure, can melt snow and ice causing flooding

• The fastest flows can reach speeds of up to 60 mph

• Eg: Mount Nyiragongo, Democratic Republic of Congo 2021 - lava flows travelled almost 10 km, destroying properties and killing over 30 people

Describe nuées ardentes as a primary hazard giving reference to a case study and further impacts?

• A more dense, red glowing type of pyroclastic flow only flowing 50km from the source

• Eg: Mount Pelée - worst volcanic disaster of the 20th century, 30,000 killed, Saint Pierre city destroyed within minutes, only 2 survivors

Describe mudflows/lahars as a secondary hazard giving reference to a case study and further impacts?

• Associated with the rapid melting of snow and ice which is found at high altitudes (gravity may affect speed).

• Fast-moving mixtures of water, volcanic ash, rock fragments, and debris flowing down the sides of a volcano and fill river valleys.

• Travel tens to hundreds of kilometers from the volcano and can be triggered way after the eruption if there is still ash and more water

• Eg: Mount Pinatubo, Philippines 1991 - Huge amounts of ash were deposited during the eruption → Seasonal monsoon rains repeatedly mixed with the ash. Lahars continued for years after the eruption, burying villages and farmland.

Describe tsunamis as a secondary hazard giving reference to a case study and further impacts?

• Eg: Krakatoa 1883 - the volcano was magnitude 6 and destroyed itself collapsing into the ocean generating a 120 feet tall tsunami (sea wave). Carried a steamship 1 mile inland, wiped out 165 villages in Java and Sumatra. 90% of people who died, died from the tsunami

Describe acid rain as a secondary hazard giving reference to a case study and further impacts?

• Forms when sulphur dioxide emitted during the eruption reacts with water vapour in the atmosphere to form sulphuric acid → acid rain

• Eg: Katmai, Alaska 1912 - harmed many ecosystems killing vegetation and animals, however, it is a rural, remote area so not many people were effected just small villages

Describe landslides as a secondary hazard giving reference to a case study and further impacts?

• Mount St Helens 1980, USA - volcano was bulging due to a blocked vent and upwelling magma so when a 5.1 magnitude earthquake struck that part of the volcano collapsed → largest landslide in history up to 249km/hr → filled Toutle River valley up to 180m deep with avalanche debris

Describe flooding as a secondary hazard giving reference to a case study and further impacts?

• caused by a sudden release of water and rocks when glacial ice is melted by the eruption

• Eyjafjallajokull was dormant for nearly 200 years but in 2010 when it exploded it melted parts of the volcano’s icecap → >140 floods → 800 people were evacuated so there were no deaths

Describe climatic change as a secondary hazard giving reference to a case study and further impacts?

• Ejection of huge amounts of volcanic ash into the atmosphere can block the sun reducing global temperatures and slowing down climate change

• Eg: 1815 eruption of Mount Tambora, Indonesia. The most powerful eruption in recorded history and directly caused the "Year Without a Summer" in 1816.

• Eg: Pinatubo 1991 - global dip in temperatures for 2 years

Describe the spatial and temporal setting at Mount Nyiragongo including plate tectonics?

• Mount Nyiragongo is in the Virunga Mountains in the Democratic Republic of Congo found along the African Rift Valley

• It is responsible for 40% of Africa’s volcanic eruptions

• Composite volcano with basaltic (fluid) lava at a constructive plate boundary - 90km/hr

• City of Goma is 20km away from Nyiragongo with 2 million people (urban population growth) + influx of refugees from Rwandan genocide

Describe and assess the risk and vulnerability of the people at Mount Nyiragongo and how that affects perception?

• Fertile volcanic soils and extended growing season - large numbers of people settled there despite the volcano. 75% of people are farmers so carry a fatalistic attitude not wanting to leave their livelihood and seeing it as

• LIC - lack of monitoring equipment and issues with looting of scientific equipment by M23 rebel group → vulnerability to CO2 seeping from the ground and inability to predict

• Political instability and violence - limited monitoring and aid from foreign governments, scientists and evacuation plans. Conflicts caused inequality where refugees lived in shanty towns on the edge of Goma vulnerable to seismic hazards

• 34 eruptions since 1882 - normalisation of risk, increased resilience of the people and learning to adapt.

Describe the preparedness and immediate response in relation to the 2002 Nyiragongo eruption?

• Unexpected - tremors were felt but largely ignored + no monitoring equipment due to political instability

• Authorities issued “Red Alert” for Goma and surrounding areas → full evacuation

• However, people complained of different messages → chaos

Describe the social and environmental effects of the 2002 eruption?

Social

• 1/3 of Goma destroyed impacting 200,000 inhabitants

• Water, power, hospital, 3 health centres destroyed

• 147 died largely due to inhaling poisonous gases/contaminated water by sulphurous lava/collapsing buildings (unlikely in HIC to die from that)

• Respiratory issues and eye irritation

• Looting from abandoned homes and properties - may cause people to not leave their homes in a future eruption

Environmental

• 5000km² of Virunga National Park destroyed - home to endangered mountain gorilla → loss of biodiversity

Describe the economic and political effects of the 2002 eruption?

Economic

• Acid rain reduced agricultural production by 60% (main source of GDP)

• Destruction of tourist economy near Lake Kivu - NGO’s estimate unemployment rose from 80% to 95%

Political

• 350,000 people fled to Rwanda (LIC) → issues with providing food and shelter → refugee crisis where people were threatened → returned home

• 1/3 of runway at Goma airport covered in lava

Assess the short and long term response to the 2002 Nyiragongo eruption?

Short term

• 2 days after eruption - UN humanitarian aid - late due to lava on airport runways - 15 million spent on providing food, blankets, shelter, water and healthcare

• Little international aid to due political instability - low GDP, slow economic growth → little investment → people having no insurance so having to rebuild on top of lava flows

Long term

• Education programme about the volcano put in place in schools

• Environmental Risk Management Unit + Goma Volcano Observatory → creation of Goma Hazards and Risks Maps

• DRC and UN made 14 evacuation camps in DRC and Rwanda and a civil defence department to stop future confusion

Evaluate the response to the 2002 eruption?

• Aid for Goma Volcano Observatory from the European Union dried up in 2014, M23 rebel group looted equipment and government doesn’t have funds

• 14 evacuation camps lacked water and medicine

Describe what happened with the 2021 eruption of Nyiragongo?

• 2021 a major vent erupted causing effusive lava to flow at 1km/hr towards Goma

• Lava flow stopped outside of Goma but cut off a major road connecting Goma and Beni

• 3 days later there were 5.3 Moment Magnitude earthquakes

• Lava detected beneath city → fears of limnic reaction - release of dissolved gases like methane

What were the social and environmental impacts of the 2021 Nyiragongo eruption?

Social Impacts

• 32 people died - toxic gases, and traffic accidents during evacuation.

• 288,000 people affected - Children missing and separated from families

• Homes + facilities destroyed → Large humanitarian crisis → aid

• COVID19, Ebola, cholera outbreaks

Environmental Impacts

• Lava flows + earthquakes destroyed villages and landscapes around the volcano

What were the political and economic impacts of the 2021 Nyiragongo eruption?

Economic Impacts

• Roads such as the N2 highway were cut off, disrupting trade and transport.

• Businesses and local livelihoods destroyed → affecting informal sector and poorest people

• City had largely recovered and grown to 4 times its size in 2002 - had largely recovered however lava flows destroyed the new houses

Political Impacts

• Thousands fled across the border into Rwanda, creating cross-border pressure.

• Concerns were raised about poor monitoring and funding issues at the volcano observatory → funding stopped by UN due to allegations of corruption

Describe the short and long term response to the 2021 Nyiragongo eruption?

Short term

• VEP city evacuation plan activated quickly

• 400,000 people (1/3 of Goma’s population) evacuated → shelters, host families + Rwanda

• 1 warning issued 14 days before the eruption → allegations of corruption and criticism → UN stopping funding

Long term

• Red Cross sent humanitarian aid and pledged to work there for a year suggesting people relocated to Sake, however this was unpopular

Compare the 2002 and 2021 eruptions?

2021 eruption was well managed - less people died and evacuation protocols were understood and implemented. However, the poorest and most vulnerable had the worst impacts as they lived at the bottom of the mountain and were most affected by the collapse of the informal sector

Even if Nyiragongo doesn’t erupt how else is the volcano a hazard?

Poisonous CO2 gases seep through the ground in large amounts killing people. The locals call this “Mazuku” and it is not uncommon