Volcanoes - physical

Question 1

where do volcanoes occur?

Answer 1

destructive plate boundaries (80%)
constructive plate boundaries (15%)
intraplate activity (5%)

Question 2

what is intraplate volcanic activity?

Answer 2

some active volcanoes exist in locations far away from plate boundaries
they are on top of volcanic hotspots
eg - hawaiian islands

Question 3

what are hotspots?

Answer 3

a plume of magma that breaks out of the mantle and to the surface
the magma plume & the point where the hot material breaks out of the crust are stationary
where it reaches the surface changes with time as plates move constantly
above the hotspot, a volcano forms and grows until the plate moves away
once it has moved, the volcano loses its source of magma & a new volcano forms over the hotspot
as volcanoes get older, they can be eroded down into seamounts

Question 4

what are the types of eruption created by a volcano?

Answer 4

effusive - basaltic magma - mid ocean ridges (hotspots)
low viscosity, travels long distance, cools slowly, frequent & gentle eruptions, lava & steam created
explosive - rhyolitic magma - subduction zones (destructive boundaries)
viscous, travels short distance, cools quickly, less frequent & violent eruptions, creates ash, rock, gas, steam & lava

Question 5

what is the VEI scale?

Answer 5

logarithmic scale - every step up on the scale represents 10x more ejected volume of material doesn’t take into account gas emissions or impacts on global climate / atmospheric conditions frequency of eruption can be determined by historical activity using volcanic deposits in the area

Question 6

what is a primary hazard of a volcano?

Answer 6

brought about by the material ejected from the volcano

Question 7

what are examples of primary hazards of volcanoes?

Answer 7

tephra - solid material ejected into the atmosphere (ash / volcanic bomb)
pyroclastic flows - very hot, high velocity gas, ash & tephra that travels very fast
lava flows - molten rock, moves very slowly but destroys everything in its path
volcanic gases - includes CO2 & CO, suffocates people

Question 8

what is a secondary hazard of a volcano?

Answer 8

occur as a result of the primary hazards

Question 9

what are examples of secondary hazards of volcanoes?

Answer 9

lahars (volcanic mudflows) - melted snow & ice mix with volcanic ash to create huge mud flows that move rapidly down river valleys
volcanic landslides - huge areas of volcanoes become loose due to volcanic activity
tsunamis - huge sea waves created by the eruptions or landslides
climate change - huge amounts of volcanic debris can impact global temperatures 
floods - melted snow & ice

Question 10

what can impacts of volcanoes be categorised into?

Answer 10

social
political - effects on the running of the area
environmental
economic

Question 11

what are short-term responses?

Answer 11

responses that are introduced immediately after the hazard to provide relief to affected people

Question 12

what do responses to hazards depend on?

Answer 12

the magnitude of the eruption
the vulnerability of the population affected

Question 13

what are long-term responses?

Answer 13

ones that attempt to reduce impacts through:
preparedness - the state of readiness for a hazard
mitigation - the action of reducing the severity / seriousness of a hazard
prevention
adaptation - the action of changing or adapting behaviour in order to reduce the severity of a hazard

Question 14

how do you manage volcanic hazards?

Answer 14

prediction
protection (preparation and planning)

Question 15

how can you predict volcanic eruptions?

Answer 15

study of past eruptions through volcanic deposits
monitoring of land swelling
changes in groundwater levels & it’s chemical composition
gas emissions
monitor seismic activity (harmonic tremors)

Question 16

what are harmonic tremors?

Answer 16

magma moves up mountain
expands cracks and breaks rock
creating small and frequent earthquakes

Question 17

how can you protect against a volcanic eruption?

Answer 17

prep and plan
risk assessments and threat levels - identify areas at highest risk of hazard
land-use planning to avoid building in high-risk areas
lava diversions (trenches, explosives, blocks & barriers) to prevent it from going into populated areas

Question 18

what is our volcanic case study? 

Answer 18

mount nyiragongo, 17th January 2002

Question 19

where is nyiragongo?

Answer 19

found in the virunga mountains in the Democratic Republic of Congo in central Africa
part of a chain of volcanoes on the southern end of a continental constructive plate margin
(African rift Valley)

Question 20

what were the effects of the eruption of nyiragongo?

Answer 20

lava covered the runway in Goma and ash made it impossible for planes to fly
a third of the city was destroyed by lava flows & 120,000 people left homeless
water pipes destroyed and drinking water polluted
1000s of people needed medical attention due to smoke inhalation and contaminated water
refugee centres were overcrowded, little food and water meant crime became a problem
destroyed power plants and fuel stores which hindered recovery massively

Question 21

what were the responses after the nyiragongo eruption?

Answer 21

food aid was flown in and given out
refugee camps were set up in Rwanda to temporarily shelter people
vaccinations given to children to avoid disease in refugee camps
red alert issued which allowed a full evacuation of Goma, so death rate was kept relatively low