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Unit 4 - Tectonic activity and Hazards
1. What are tectonic hazards and what causes them?
A tectonic event is a physical occurrence resulting from the movement or deformation of the Earth's crust.
They are predominantly earthquakes or volcanic eruptions and their associated activities. Such events can
become tectonic hazards…

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0 < 10,000 m³ Hawaiian effusive constant Kilauea, Piton de la Fournaise many
1 > 10,000 m³ Hawaiian/Strombolian gentle daily Stromboli, Nyiragongo (2002) many
Galeras (1993), Mount
2 > 1,000,000 m³ Strombolian/Vulcanian explosive weekly 3477*
Sinabung (2010)
> 10,000,000 Nevado del Ruiz (1985),
3 Vulcanian/Peléan severe few months 868
m³…

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Global distribution of earthquakes and volcanoes is shown here.

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Tsunamis (`harbour waves' ­ Japanese) are waves caused by the rapid movement or deformation of the
seabed. Submarine earthquakes, volcanoes, landslide or slumps can initiate this motion. They are classified as
secondary hazards since they are events cause by a tectonic occurrence.
The distribution of earthquakes and volcanoes has a…

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Formed by major mantle plume of rising that may cause a
The Isle of Arran ­ west
eruptions from vents or magma, volcanic hot dooming up of the
coast of Scotland,
fissures. Accumulation of spot Reunion in Indian surface as they form.
intrusion of large granite
deposition = layers Ocean,…

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steep sides and andesite
magma forms here with
cinders, bombs and
blocks add height to the
volcano, some can be up
to 8,000 feet above
base.
Destructive Western coast South
(convergent) boundary America ­ Nazca plate
volcano: subduction subducted beneath
zone causes build up of continental South
pressure beneath the…

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Microfracturing is also common as the effects of earthquakes on landscapes ­ also known as microseismicity.
Explained as the process of small-scale fractures on very small areas releasing stress under high-strain
conditions. Sufficient when microfractures link up to a large slip surface of significance seismic event or
earthquake can occur.…

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Volcano ­ e.g. explosive blast, lava flows, ash flows and ash falls, mud flows (lahars), and the release
of poisonous gases
ETC
Some areas show concentrations of tectonic and other hazards. These are known as multiple hazard zones.
For example, The Philippines in southwest Asia is at risk froma number…

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Social Human costs, e.g. primary, secondary and tertiary casualties. Hazards can also cause
misery and suffering as well as poor health, e.g. loss of electricity/ services/
infrastructure
Economic Costs of repairing damage. Indirect costs/secondary impacts, such as loss of
earnings, loss of tourism income


Tectonic hazards can have beneficial impacts…

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Range of responses:
The response to natural hazards can occur at a range of scales, from the individual within the local community
to regional, national and international level. Various `players' may be involved in hazard response.




National National policies, civil protection and defence with a thorough check of the information…

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