Lecture 2: Volcanic hazards 2

Question 1

Divergent extensional zones

Answer 1

neighbouring tectonic plates- moving apart- rifting-new lithosphere is being generated - by upwelling magma

D zones are mostly submarine- MAR- some appear on land e.g. iceland

Question 2

Convergent compressional zones

Answer 2

ocean lithosphere- of one plate- subjects beneath another

sediments with - h20 and co2- dragged down with defending plates-impurities lower- melting temp of rock

magma forms and rises due to lower density

Question 3

Intraplate (Hotspot)

Answer 3

you know this

Question 4

magma consists of

Answer 4

liquid portion- aka melt

solid portion- made of minerals- crystallised directly from melt

solid rock- incorporated- into magma from along- the conduit or reservoir- aka xenoliths or inclusions

dissolved gasses- volatiles

Question 5

magma characteristics

Answer 5

learn from iPad

silica and gas content

Question 6

VEI

Answer 6

look at iPad

Question 7

Tephra

Answer 7

tephra- fragments of volcanic rock and lava- blasted into the air by explosions- or - carried upwards by hot gases in eruption collums or lava fountains

Question 8

tephra- ash plume

Answer 8

iceland- air plane damage- whinshelid damage- ash in engines- abrasion of fan blades- engine failure

Question 9

volcanic gases

Answer 9

contain c02, sulphur dioxide- affects humans and plants

lake nyoos cameroon- rapid co2 release- 1,700 fatalities

directly responsible for 3% of volcano related deaths 20th century

Question 10

lava flows

Answer 10

little threat

slow moving - 90% are basaltic

zaire- rapid downhill up to 60km/hr- small village- 70 deaths

Question 11

Pyroclastic flows

Answer 11

high density of hot gases ashes and cinders

dense cloud- moves away from vent- at high speed- travels across ground at 80km/hr

contains rock fragments- ash to boulders

temp- 200-700c

Question 12

more pyroclastic flows

Answer 12

most common direct cause of death in last 400yrs

death by- burial-burns-obliteration-trauma

Question 13

lahars

Answer 13

hyper concentrated mud flow- high density- up to 75% solid

very erosive- pick up material- downhill- occur after or during eruption

Question 14

secondary effects- tsunamis

Answer 14

santorini greece 1638 bc- destruction of minoan civilisation

Question 15

hawaii risks

Answer 15

very freq eruptions

more than 100 ppl killed- only 1 death 20th century - lava flows v destructive

Question 16

probalisitic forecasting

Answer 16

freq of occurrence x (1 divided by magnitude )