70+ A* marked AQA Geography:
Hazards questions and model
answers
written by
mekkiexox
www.stuvia.com
Downloaded by: mekkiexox | Want to earn £756
Distribution of this document is illegal extra per year?
, Stuvia.co.uk - The Marketplace for Revision Notes & Study Guides
HAZARDS - much cheaper on
etsy. search 'mekkieprints'
Analyse the role of plate margin type in influencing the risk
posed to people by volcanic hazards (9 marks)
There are three types of plate margins: constructive (involves two plates moving away from each
other), destructive (involves two plates colliding with each other) and conservative (involves two
plates sliding past each other). However, it is only at constructive and destructive boundaries where
volcanic activity occurs.
At constructive plate boundaries, basaltic lava is formed. Due to its low silica content, it has a low
viscosity and so can flow quickly, extending tens of kilometres from an erupting vent, resulting in
relatively gentle but frequent eruptions. Having a low viscosity also means basaltic lava is associated
with pyroclastic flows and ash fallout. Rapid lava flows at constructive plate margins pose a very high
risk to people because they travel faster so they cover a larger distance than slower flows, meaning
there would be higher levels of destruction to the surrounding land and infrastructure. When basalt
lava flows are confined within a channel or lava tube on a steep slope, the main body of the flow can
reach velocities over 30 km/h, reducing the amount of time for nearby people to evacuate and
therefore posing a higher risk.
At destructive plate boundaries, andesitic lava is formed. Due to its high viscosity, andesitic lava
flows are slower (travelling at only a few kilometres per hour) and therefore cover shorter distances.
Their eruptions may be less frequent than basaltic ones, but they are more violent because of gas
build up. Andesite lava can generate strong explosive eruptions to form fast-flowing pyroclastic
flows, Pyroclastic flows vary considerably in size and speed, but even relatively small flows that move
less than 5 km from a volcano can destroy buildings, forests, and farmland. On the margins of
pyroclastic flows, death and serious injury to people and animals may result from burns and
inhalation of hot ash and gases, however deaths caused directly by andesite lava are uncommon
because it moves slowly enough for people to evacuate. A well-resourced nation would be at a lower
risk because they have higher levels of preparedness (e.g. advanced equipment, a predetermined
procedure. Etc) and therefore can mitigate against this impact effectively.
In conclusion, the risks associated with different types of plate boundaries can pose varying levels of
risks to people, depending on the type of plate margins and whether volcanic activity can occur there
or not, type of lava erupted and its viscosity and how it travels (through a confined channel or as a
broad sheet).
Assess the importance of governance in the successful
management of tectonic hazards (20 marks)
A sudden volcanic eruption of Mt Ontake occurred on Saturday 27th September 2014 on the main
island of Honshu, Japan. It was thought to be dormant (an active volcano is not erupting but is
supposed to erupt again) until 1979, where it underwent a series of minor eruptions. These small
eruptions were meant to signal an impending eruption. However, this was not detected, and Mt
Ontake erupted without warning, causing chaos and danger amongst the tourists, hikers and
climbers that the mountain is popular with.
Downloaded by: mekkiexox | Want to earn £756
Distribution of this document is illegal extra per year?
Hazards questions and model
answers
written by
mekkiexox
www.stuvia.com
Downloaded by: mekkiexox | Want to earn £756
Distribution of this document is illegal extra per year?
, Stuvia.co.uk - The Marketplace for Revision Notes & Study Guides
HAZARDS - much cheaper on
etsy. search 'mekkieprints'
Analyse the role of plate margin type in influencing the risk
posed to people by volcanic hazards (9 marks)
There are three types of plate margins: constructive (involves two plates moving away from each
other), destructive (involves two plates colliding with each other) and conservative (involves two
plates sliding past each other). However, it is only at constructive and destructive boundaries where
volcanic activity occurs.
At constructive plate boundaries, basaltic lava is formed. Due to its low silica content, it has a low
viscosity and so can flow quickly, extending tens of kilometres from an erupting vent, resulting in
relatively gentle but frequent eruptions. Having a low viscosity also means basaltic lava is associated
with pyroclastic flows and ash fallout. Rapid lava flows at constructive plate margins pose a very high
risk to people because they travel faster so they cover a larger distance than slower flows, meaning
there would be higher levels of destruction to the surrounding land and infrastructure. When basalt
lava flows are confined within a channel or lava tube on a steep slope, the main body of the flow can
reach velocities over 30 km/h, reducing the amount of time for nearby people to evacuate and
therefore posing a higher risk.
At destructive plate boundaries, andesitic lava is formed. Due to its high viscosity, andesitic lava
flows are slower (travelling at only a few kilometres per hour) and therefore cover shorter distances.
Their eruptions may be less frequent than basaltic ones, but they are more violent because of gas
build up. Andesite lava can generate strong explosive eruptions to form fast-flowing pyroclastic
flows, Pyroclastic flows vary considerably in size and speed, but even relatively small flows that move
less than 5 km from a volcano can destroy buildings, forests, and farmland. On the margins of
pyroclastic flows, death and serious injury to people and animals may result from burns and
inhalation of hot ash and gases, however deaths caused directly by andesite lava are uncommon
because it moves slowly enough for people to evacuate. A well-resourced nation would be at a lower
risk because they have higher levels of preparedness (e.g. advanced equipment, a predetermined
procedure. Etc) and therefore can mitigate against this impact effectively.
In conclusion, the risks associated with different types of plate boundaries can pose varying levels of
risks to people, depending on the type of plate margins and whether volcanic activity can occur there
or not, type of lava erupted and its viscosity and how it travels (through a confined channel or as a
broad sheet).
Assess the importance of governance in the successful
management of tectonic hazards (20 marks)
A sudden volcanic eruption of Mt Ontake occurred on Saturday 27th September 2014 on the main
island of Honshu, Japan. It was thought to be dormant (an active volcano is not erupting but is
supposed to erupt again) until 1979, where it underwent a series of minor eruptions. These small
eruptions were meant to signal an impending eruption. However, this was not detected, and Mt
Ontake erupted without warning, causing chaos and danger amongst the tourists, hikers and
climbers that the mountain is popular with.
Downloaded by: mekkiexox | Want to earn £756
Distribution of this document is illegal extra per year?
