Volcanic Activity

Question 1

Constructive margin
-cause-lava type-nature-form-

Answer 1

Cause: Decompression melting - partial melting of asthen resulting from fall in pressure as cc rises

Lava: Basaltic
Runny gases can easily escape

Nature: •Rarely explosive gases less likely to be trapped
•eruptions dominated by lava flows
• eruptions more frequent and continuous

Form: Shield (gently sloping)

Question 2

Destructive margin
-cause-lava type-nature-form-

Answer 2

Cause: Subduction Melting
Hydration Melting

Lava: Andesitic or Rhyolitic
Very viscous gases cannot escape easily

Nature:
•Explosive - trapped gas blows magma apart
•Some Lava, Explosive materials
•less frequent - vents blocked by viscous magma

Form: composite (steeper more localised)

Question 3

Hotspot Processes

Answer 3

Volcanic activity produced by mantle plume (conventional flow of heated rock in asthen)

Mantle plume rises magma is produced by partial melting of asthen resulting from fall in pressure

Magma less dense than asthen and hot enough to melt litho - rises to erupt at surface
further eruptions cause volcano rise above sea =volcanic island directly above hotspot

Question 4

Pattern of Hotspot islands

Answer 4

Mantle plume stays static

Pacific plate above it moving SE to NW - island gradually moves away from hot spot - volcano extinct

As part continues to move - new portion of lithosphere now over hotspot - same processes create another volcanic island

Process repeats forming linear pattern of island - only last volcanic island in pattern active

Question 5

Lava Flow Socioeconomic Hazard

Answer 5

Slow moving does not threaten human life

Destroys property and farmland - economic impacts

1973 Heimaey Iceland

Question 5

Pyroclastic flow Socioeconomic Hazards

Answer 5

Responsible for more deaths than any other

Pompeii 79 AD

Proceeded by airblast that can topple buildings
Heat can set fire to buildings
-economic effect

Question 6

Lava Flow Environmental Hazards

Answer 6

devestate natural environment
All veg covered completely - destroying it and habitats it provided

Question 7

Pyroclastic flow environmental hazards

Answer 7

Short term devastate natural environment
All veg covered completely destroying it and habitats

Mt St Helens 1980

Question 8

Lahars

Answer 8

Volcanic mudflows when volcanic material mixes with water
Up to 100km-1

When stopped - quickly set and solidify burying anything in path

Question 9

Lahars socioeconomic hazards

Answer 9

2nd biggest cause deaths
Nevado el Ruiz 1985

Damage and destroy buildings infra, crops and livestock

Question 10

Lahars environmental hazards

Answer 10

Bury land in deposits of mud metres in depth

Nevado El Ruiz 1985

Question 11

Tephra and Ash Clouds

Answer 11

Largest : Volcanic Bombs

Smallest : Volcanic Ash

Question 12

Tephra Ash Clouds socioeconomic hazards

Answer 12

Deaths from ash rare - local conditions can make it more hazardous - Mt Pinatubo

Ash cause buildings collapse - economic loss and death

Fine ash ground planes cause sig econ losses

Question 13

Tephra ash clouds environmental hazards

Answer 13

1991 Pinatubo so much ash into atmosphere that temp across world affected

Summer temperatures in Europe following year 2C lower than avg

Question 14

Poisonous Gas socioeconomic

Answer 14

CO2 escaped from Lake Nyos Cameroon 1986. Sank down slopes of volcano killing 1700 people and 8000 livestock

Question 15

Poisonous Gas environmental

Answer 15

Slow release CO2 and SO2 can destroy plants

Mammoth Mountain, USA

Question 16

Jökulhlaup

Answer 16

Flood caused by glacial melting associated with volcanic eruption

Question 17

Jökulhlaup socioeconomic

Answer 17

Waters cause sig damage infrastructure

Grimsvötn Iceland 1996 - close monitoring = people evacuated in time

Question 18

Jökulhlaup environmental

Answer 18

1996 Grimsvötn caused sig subsidence of the glacial lake

Question 19

SOCIOECONOMIC BENEFITS VOLCANIC ACTIVITY

Answer 19

•Fertile Soils Supporting Agri
•Mineral Creation and Extraction
•Tourism

Question 20

Fertile soils supporting agri

Answer 20

Longer term - ash and tephra improve soil fertility - incr agri productivity

Naples most fertile soils compared to rest of Italy due to Mt Vesuvius

Question 21

Mineral Creation and Extraction

Answer 21

Commercial purposes

Pumice - abrasive in soaps and household cleaners

Ash and Pumice - aggregate in making of cement

Valuable Metals- Gold Uranium
Precious Stones- Opals Onyx

Boost economy and provide employment for locals

Question 22

Tourism

Answer 22

Boost economy

Ruins if Pompeii 2 million annual visitors

Giants Causeway 60mil y/o 850,000 visitors 2015

Question 23

ENVIRONMENTAL BENEFITS

Answer 23

Land Creation
Geothermal Activity

Question 24

Land Creation

Answer 24

Volcanic eruptions create new land - Hawaii & Antilles archipelago in Caribbean Unique plants and animals adapted to living - increase global biodiversity

Question 25

Geothermal Energy

Answer 25

Heat rising in crust harnessed for power generation 51% energy needs in Kenya Release small fraction of CO2 released from conventional fossil furl plants **Reliable, Sustainable and Relatively Non Polluting**