Hazards: Volcanoes

Question 1

Where do volcanoes occur?

Answer 1

• on or near subduction zones (destructive)
• middle of plates - hotspots
• ocean ridges and rift valleys (constructive)

Question 2

How do volcanic hazards differ?

Answer 2

• the shape and structure of the volcano and the explosive threat they pose is the result of the type of magma that created them.
• the destructively of a volcano depends on the viscosity (funniness) of the magma
  —> low viscosity (runny magma) - shallow sided volcanos
  —> high viscosity (sticky, thick magma) - steep sided volcano

Question 3

What are the 3 things viscosity is affected by?

Answer 3

1. Temperature (runny magma will be hotter)
2. Silica content (the more silica there is, the thicker)
3. Gases (more explosive)

Question 4

What is basaltic lava?

Answer 4

Hot, low viscosity, non-violent eruptions, flat cones, lava spreads far from volcano, melting of oceanic crust and the mantle so occur at constructive margins and hotspots (island arcs).
—> e.g. Kilauea (Hawaii), Mauna Loa and Surtsey

Question 5

What are the 2 types of Basaltic lava?

Answer 5

Aā - forms as spikey lava
Pāhoehoe - soft, pillowy lava

Question 6

What is Andesitic lava?

Answer 6

High eruption plumes, intermediate lavas formed by rising basaltic magma mixing with continental crust before it reaches the surface resulting in violent eruption, this lava is largely formed at subduction zones.

Question 7

What is Rhyolitic lava?

Answer 7

Thick, viscous lava, secondary vent form, sudden and violent eruptions.
High silica content are formed from the melting of continental crust so form at destructive boundaries.
- e.g. Mount Fuji (Japan) and Mount Pelée (Caribbean)

Question 8

What are the 2 types of volcano?

Answer 8

• Shield or basic volcano (sloped) -e.g. Mauna Loa, Hawaii
• Composite (steep sided) -e.g. Mt St Helens

Question 9

How can the magnitude of volcanos be measured?

Answer 9

They can be measured using the Volcanic Explosivity Index (VEI)
- 0 (non-explosive) - 8 (very large).
- Logarithmic- each interval on scale represents a tenfold increase in the violence of the eruption:
1. Gentle
4. Cataclysmic
8. Mega-colossal (supervolcano)
—> multiple features considered when calculating VEI, e.g. how much tephra erupted and how high it ejected, how long it lasts, etc.

Question 10

What is the frequency of volcanos?

Answer 10

• varies per volcano.
• either active, dormant or extinct. ​estimated ​50-60 volcanoes erupt each month​, meaning eruptions are frequent (some volcanoes erupt constantly). Usually, a higher frequency eruption means effusive​ whereas low frequency means explosive.

Question 11

What is the regularity of volcanos?

Answer 11

Volcanic eruptions are regular in that the eruptions on ​each type of boundary are similar (e.g. eruptions on destructive boundaries will regularly be explosive)
- Sometimes eruptions may be irregular and not fit patterns.

Question 12

What is the predictability of volcanos?

Answer 12

Regularity of eruptions help estimate when eruptions take place (i.e. every 10 years). Seismic activity, gases releasing, elevation etc. all indicate imminent eruption, but no ​definite​ predictions to a volcanic eruption.

Question 13

What are lava flows? (Primary hazard)

Answer 13

A flow of molten rock or magma
- a lava flow may destroy farmland, buildings and lines of communication, but lives are rarely lost

Question 14

What is ash (tephra)? (Primary hazard)

Answer 14

Fine-grained ash with larger pyroclastics may be ejected into air during violent eruption
- weight of depositied ash can cause roofs of buildings to collapse
- suffocation of humans and animals
- can wipe out crops and block roads
- blocks solar radiation so cooler temps
- in last 15 years, about 80 commercial jets damaged flying through ash
—> e.g. Mount Marapi (Indonesia)

Question 15

What is pyroclastic flow/Nuée Ardente? (Primary hazard)

Answer 15

Most dangerous/devastating, a cloud of gas, ash and rocks, can reach temps of 800DC and capable of speeds in excess of 200km/hour
- broken rock with newly released gases sweep down volcano, obliterating everything in its path.
—> e.g. Mt St Helens (USA) in 1980, north face collapsed to unleash a blast -felled fully grown trees upto 25km away.
- if involves mainly gases, often in form of a fireball is a Nuee Ardente - this killed nearly 30,000 people when Mt Pelee erupted.

Question 16

What are Lahars (mudflows)? (Secondary hazard)

Answer 16

A lahar is a thick, cement-like mudflow of volcanic ash and water (often melted snow/ice that once capped the volcano). Capable of flowing at speeds of 100km/hour and distances of 300km.
- commonly follow river valleys, burying houses and occupants, blocking roads and destroying bridges, also blanketing fertile floodplains with thick mud that hardens like concrete
—> e.g. Nevada del Ruiz killed 1000s of people in the town of Armero

Question 17

What is acid rain? (Secondary hazard)

Answer 17

gases such as sulphur dioxide are released, volcanic acids react with water vapour in atmosphere.
- can damage ecosystems and can also cause stone and metal to deteriorate, damaging buildings, bridges, etc.
—> e.g. Tongas Volcano eruption

Question 18

What is a jokulhlaups (glacial outburst floods)? (Secondary hazard)

Answer 18

When temps are high from magma (if volcano erupts beneath an ice cap), glaciers or ice sheets quickly melt and large amount fo water is discharged.

Question 19

What is some of the equipment used to help countries with volcanoes?

Answer 19

• seismograph/seismometers - measures seismic activity —> micro earthquakes indicate magma fracturing and cracking the overlying rocks
• tiltometers and laser-based electronic distance measurements - measures ground deformation —> bulging of the ground is magma rising, both slope angles and the increasing distance between set points can be measured very accurately
• magnetometer - measures upward movement of iron-rich magma —> changing magnetism within the volcano is a common indication of rising magma
• sampling gas and lava emission (e.g. Mount Etna - sulphur dioxide)
• hydrology - ground water level and chemical composition
• seismicity - using shock waves produced from magma rising to predict time of eruption (e.g. Popocatepetl, Mexico 2000, where 30,000 residents were evacuated 48 hours prior) - yet unlikely for all volcanos
• remote sensing and GPS

Question 20

What are the primary environmental impacts of a volcanic hazard?

Answer 20

• ecosystems damaged through various volcanic hazards
• wildlife killed

Question 21

What are the primary economic impacts of volcano hazards?

Answer 21

• businesses and industries destroyed or disrupted

Question 22

What are the primary social impacts of volcanos?

Answer 22

• people killed
• homes destroyed from lave/pyroclastic flows

Question 23

what are the primary political impacts of volcanos?

Answer 23

• gov buildings and other important areas destroyed or disrupted

Question 24

What are the secondary environmental impacts of volcanos?

Answer 24

• water acidified by acid rain
• volcanic gases contribute to greenhouse gas effect (global warming)

Question 25

What are some secondary economic impacts of volcanos?

Answer 25

• jobs lost
• profit from tourism industry (eruptions can attract tourism)

Question 26

What are the secondary social impacts of volcanos?

Answer 26

• fires can start which puts lives at risk
• mudflows or floods
• trauma
• homelessness

Question 27

What are the secondary political impacts of volcanos?

Answer 27

• conflicts concerning gov response, food shortages, insurance, etc.

Question 28

How can volcanos be prevented?

Answer 28

• its not possible to prevent a volcano from erupting
  —> however it is possible to prevent hazards posing a risk to people, e.g. by preventing land around a volcano from being developed

Question 29

How can you prepare from a volcano?

Answer 29

preparedness is about what happens before an eruption to minimise risk or vulnerability
- monitoring systems to predict when it may occur, so warning can be given
- education on volcanos in the area, so people know what to do if there is a volcanic eruption
- evacuation procedures planned
- training response teams
—> e.g. alert levels in the UAS and New Zealand, hazard mapping in the Cascade Range, USA

Question 30

How can a volcano be mitigated?

Answer 30

• direct intervention to the volcano, e.g. concrete blocks to steer lava away from areas at risk
• strengthening buildings that are at risk of mudflow or ash pileup
• evacuation and exclusion zones
• mitigating effects on health by having emergency aid and rescue
  —> e.g. lava diversions for Mount Etna, Sicily and cooling down lava with water, Heimaey, Iceland

Question 31

How can people adapt from a volcano hazard?

Answer 31

• move away from areas at risk
• capitalise on opportunities, such as encouraging tourism, or farming (volcanic ash makes soil very fertile)
• change profession so it is less likely to be affected by volcanic hazards

Question 32

What was the nature of the volcanic hazard of Eyjafjauajökull (E15)?

Answer 32

• lava (fissure eruption)
• volcanic ash cloud
• flooding (jokulhlaup - glacial outburst flood) - E15 was under a glacier.
  —>the melted ice cooled the material ejected from the volcano to form a glassy ash with 58% silica (much higher than normal)
  —> very fine ash, so the % of ash being transmitted over a long distances was very high
  —>the magma melted overlying ice cap so water flowed into the crater, adding to its explosivity

Question 33

Where is E15 located?

Answer 33

Iceland - which sits on the Mid-Atlantic ridge and split in two - to its east, the Eurasian plate is moving Eastwards, whilst the west of Iceland is moving Westwards with the North American plate (so this volcano is on a constructive plate boundary)
Although iceland is also thought to be over a hotspot
— E15 is the south of Iceland and is 1660km high and 20km from its famous sister, Kalta

Question 34

What were some of the local impacts from E15?

Answer 34

• local pop was evacuated for safety and because of respiratory threats due to ash
• flooding of local roads and farmlands (jokulhlaup)
• fresh fish exports, a major local industry, were badly affected with the loss of income
• livestock taken inside to escape the ash (economy and businesses will be affected - at least short term)
• locals struggled to breathe normally, dust and ash everywhere
  —> locally it wasn’t a bad disaster, only short term problems. As a HIC, they had help and resources prepared to help

Question 35

What were the regional impacts of E15?

Answer 35

• all flights cancelled from certain airports or certain days
• ash got into jet engines (causing it to shut down). Airlines losing millions of pounds a day
• shares in airlines and travel business fell
• Europe lost €2.6 billion of GDP due to eruption. Also suffers an 11.7% drop in air passenger numbers
• occurred at the end of Easter break, so many people were stuck abroad (400,000 Britain’s stranded worldwide)
  + the channel tunnel and the cross channel ferries did a lot of extra business whilst ash was around

Question 36

What were some of the further afield impacts of E15?

Answer 36

• Barack Obama could not get to Poland for the state funeral of the Polish President
• the closure of Europe’s airport hubs paralysed global air travel
• the Prime Minister of Norway had to run his country from New York as there were no transatlantic flights to Northern Europe for several days - on his ipad
  + due to reduction of air traffic, 2.8 million tonnes less of CO2 was emitted during the period

Question 37

What were the wider impacts of E15?

Answer 37

• LICs affected - Kenya - 20% of their economy relies on perishable exports like green vegetables and cut flowers to Europe.

Question 38

How was E15 managed?

Answer 38

• expert monitoring
• collaboration between professional bodies and countries
• capacity to make predictions and contingency plans
• resilience (financial, transport links, food supply and agriculture, legal)
• insurance

Question 39

What were the short term responses and risk management in Montserrat (1995)?

Answer 39

• warning systems were set up to alert inhabitants - sirens, speaker systems and via the media
• Montserrat Volcano Observatory, set up in 1995, successfully predicted its eruption in June 1997
• £17 million in UK aid paid for temporary buildings and water purification systems

Question 40

What were the long term responses and risk management in Montserrat?

Answer 40

• a 3 year redevelopment programme for houses, schools, medical services, infrastructure and agriculture was funded by the UK
• by 2005, many people have moved back, but the south, including Plymouth remained in exclusion zone
• UK financial aid since 1995 has exceeded £420 million