Summary
Summary detailed notes for OCR advanced information 'Hazards'
- Module
- Hazardous earth
- Institution
- OCR
is a complete document for all information needed case studies are Montserrat, Iceland, Haiti and Japan
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Hazardous Earth2.a.
- explosive eruptions: convergent plate boundaries, rhyolite and andesite lava, acidic and high
viscosity lava which is at a lower temperature, violent bursting eruption, it can eject
gas,dust,ash,lava,bombs and tephra, eruptions do not occur regularly, the volcanoes are often steep
sided, stratovolcanoes or caldera volcanoes
- effusive eruptions: divergent plate boundaries, basaltic lava, low silica and low viscosity lava which
is at a higher temperature at the point if eruption, eruption is flowing with limited explosive force, it
ejects gas and lava, eruptions are frequent and can last months, occur from gently sloping shield
volcanoes
- hot spots: fixed area of intense volcanic activity where magma reaches the surface, as the tectonic
plate moves over the hot spot islands form, for example the Hawaiian chain of islands, the east
African rift valley is 4000km long and contains several active volcanoes over the past 30 million years
the crust has been uplifted and stretched which causes tension in the rocks and causes rifting with
magma forcing its way up to the surface to create volcanoes e.g. Kilimanjaro
- super volcanoes: a volcano that erupts more than 1000km^3 of material in one eruption e.g.
Yellowstone and has a VEI of 8
- shield and fissure volcanoes: typically found at constructive plate margins and are made of basaltic
lava
- dome, strato, compositive and caldera volcanoes: typically found at destructive plate margins and
are made of andesitic lava
- VEI: a logarithmic scale which goes up to 8
2.b.
- lava flows= impact depends on type of lava, basaltic lava can flow long distances which increases
impacts, acidic lava is thick and everything in the path of the lava will be either burned, bulldozed, or
buried
- pyroclastic flows= combination of very hot gases and rock fragments travelling at high speed, they
are highly destructive, and inhalation causes almost instant death
- tephra= material ejected from the volcano into the air, ranges in size from fine ash to large volcanic
bombs, potentially very hazardous, eruption columns can carry material into the stratosphere
- toxic gases= volcanoes emit a wide range of toxic gases including Co,CO2 and SO2 which can be
deadly to human populations
- lahars: mud flow with consistency of wet concrete
- floods: volcanic eruption beneath an ice field or glacier causes rapid melting
- tsunami: eruption of some island volcanoes can causes massive displacement of ocean water and
tsunami waves can form
Most volcanic hazards are short term, large quantities of ash can lead to long term climate change
, 3.b.
- ground shaking and ground displacement: vertical and horizontal movement of the ground, the
severity of ground shaking depends on magnitude, geology and distance from epicentre, locations
that are close to the epicentre of a high magnitude quake where the surface layers are relatively
unconsolidated and have a high-water content will have extreme ground shaking, the displacement
of the surface can also disrupt natural drainage
- liquefaction: when an earthquake strikes an area where surface materials consist of fine grained
sands and landfill with a high water content the vibrations can cause the material to behave like
liquids
- landslides and avalanches: ground shaking and liquefaction an cause slope failure which leads to
landslides, they can make access for aid difficult and can block rivers which can cause floods
- tsunamis: underwater earthquakes can cause a vertical rise in the seabed which displaces water
above and causes tsunami waves, underwater landslides caused by earthquakes also displace water
and create tsunami waves, tsunamis lead to flooding
4.a.
Iceland:
-Eyjafjallajökull erupted in April 2010, it’s on a hot spot and a divergent plate boundary (mid-Atlantic
ridge), eruption had a VEI of 2
-People choose to live there because: fertile land for agriculture, the land is flat for building,
opportunities for geo-thermal energy, opportunities for hydro energy, beautiful views, tourism
-social impacts: rural people ‘downwind’ had to wear masks and goggles to protect themselves from
the ash, 500 cattle farmers and families had to be evacuated, roads were closed, ash contaminated
the local water supply, global news reported the eruption which showed the beauty of the Icelandic
landscape which then increased tourism in the following years, ‘Inspired by Iceland’ was launched in
2011
-political impacts: CAA were criticised by airlines for closing airspace too hastily and for too long,
after this engineers and volcanologists have investigated how planes can be adapted to fly through
ash, ‘future volc’ set up with Europe and Iceland which established a monitoring system
-economic impacts: airlines lost a combined £130 million/day in revenues, tourist businesses lost
between £5 million and £6 million/day, Eurostar saw an increase in passengers by nearly 1/3
(positive), Nissan had to halt production of one of their models for a day because they couldn’t get
the parts, Kenyan horticultural industry lost an average $3million/day, some 3,000 tonnes of fresh
flowers which were intended for the UK market were left to rot because air space was closed
-environmental impacts: ash deposited into the North Atlantic ocean triggered a phytoplankton
bloom, grounding of flights reduced emissions (2.8 million tonnes of carbon were not emitted),
major glacial outburst flood (jokulhlaups) caused 700 people to be evacuated, livestock grazing is
difficult in Iceland and due to the eruption animals had to be moved inside
Montserrat:
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