Volcanic case studies - LIC Nyiragongo, Congo Flashcards
Describe the spatial and temporal setting of the eruption?
17th January 2002, The Democratci Republic of the Congo. VEI 1
Why did the event occur?
The release of tension at a constructive plate boundary at the African Rift Valley system. 250m deep and 2km wide crater that often contains a lava lake on the flank. Due to basaltic lava; release of a lava lake there was rapid lava flow of over 40mph.
How did people perceive the eruption?
Responsible for 40% of all Africa’s eruptions and has erupted frequently however tend to be gentle and slow so that it is a low threat to people. Additionally very fertile soil means costs outweigh benefits. However this eruption was unexpected.
What were the impacts of the eruption?
Lava flows destroyed ⅓ of Goma, including water and power facilities and the medical centre.
147 killed most from inhaling poisonous gases, drinking contaminated water and collapsing buildings.
What were the responses to the eruption?
Red alert for Goma and the surrounding area
Local authorities struggled to respond due to low 2 days post eruption UN brought in Humanitarian emergency aid.
The UN set up camps to house displaced people and provide medical care - estimated cost of $15 million.
Give three things that affect the speed of lava flow.
Temperature (higher temperatures flow further)
Viscosity of the lava (lower silica content/low viscosity flow further)
Steepness of slope (steeper slopes flow further).
Outline why high gas content makes volcanic eruptions explosive.
Higher gas content: as magma emerges from the vent > depressurisation causes gas to quickly expand > explosive eruptions.
Outline why high silica content makes volcanic eruptions explosive
Higher silica content > higher viscosity: lava blocs vents > pressure builds up > suddenly released in an explosive eruption.
Give three methods of diverting lava flows?
Digging/using explosives to create earth trenches and use concrete: Mt Etna Sicily
Bombing lava tubes
Use of ice water/cooling lava: 1973 Heimaey Iceland
How might people adapt to the risk of volcanic eruptions?
Strengthen buildings to reduce the chance of collapse from ash on roofs
Capitalize on the opportunities of living near volcanoes e.g. farming fertile soils or working in the tourism industry.
Give three primary impacts of volcanic events
People are killed and buildings are destroyed by pyroclastic flows
Ash causes damage to agricultural land
Ash causes flights to be grounded
Give three secondary impacts of volcanic events
Acid rain acidifies aquatic ecosystems killing some plants/animals
Volcanic debris reflects sunlight resulting in crop destruction due to colder winters
Flash floods due to glacial melts
