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Geography > Geophysical Hazards > Flashcards

Geophysical Hazards Flashcards

1
Q

what is the structure of the earth from outside to in

A
  • thin rigid crust, composed of the continental crust and thinner oceanic crust
  • underneath is a flowing but solid mantle that makes up 82% of the volume of the Earth
  • Deeper still is a very dense and very hot core:
    -> outer core is liquid
    -> inner core is solid

These concentric layers become more dense in the centre, and are controlled by temperature and pressure

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2
Q

what is the asthenosphere?

A

the layer underneath the lithosphere

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3
Q

what is the plate tectonics theory

A

the theory that the outer shell is divided into several plates that glide over the mantle, called the continental drift -> first proposed by scientist Alfred Wegener in 1912

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4
Q

where does the earth’s heat come from?

A

The flow of heat from the Earth’s interior to the surface comes from 2 main sources:

  • Radiogenic -> radioactive decay of material in the mantle and the crust
  • Primordial heat -> the heat lost by the Earth as it continues to cool from its original formation
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5
Q

what are the 3 mechanisms related to plate movement?

A
  • subduction
  • plume
  • rifting
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5
Q

how to convection currents operate

A
  1. hot magma rises through the core to the surface
  2. and spreads to the mid-ocean ridges
  3. the cold solidified crust sinks back because it is heavier and denser than the surrounding metal
  4. the cause of the movement is radioactive decay of uranium and potassium in the mantle
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6
Q

what is subduction?

A

subduction refers to the plunging of one plate below another

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7
Q

what is the process of subduction

A
  1. oceanic lithosphere plates collide with another plate - whether is continental or oceanic
  2. The oceanic plate is a lot denser than the continental
  3. the subducting plate is forced to subduct and creates a subduction zone
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8
Q

what is a plume?

A

refers to a small area of unusually high heat flow. Plumes can cause movement (the outward flow of viscous rock from the centre) that may create a drag force on the plated causing them to move. Most occur on a plate boundary, such as the Hawaiian Hotspot

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9
Q

what is rifting?

A

Rifting occurs at constructive plate boundaries, where magma rises and pushes two plates away from each other, for example, the North American and Eurasian plates are moving away from each other.

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10
Q

what is believed to be the main cause of rifting?

A

hotspot activity

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11
Q

where are volcanoes located?

A

most are found usually over plate boundaries, however, there are some exceptions, i.e. volcanoes in Hawaii form over hotspots

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12
Q

where in the world are they distributed?

A

most around the Pacific Ring of fire

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13
Q

what are the 3 different types of volcanoes?

A
  • shield
  • composite
  • cinder
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14
Q

how do shield volcanoes form?
what do they look like?
are they explosive?
example

A
  • formed from very hot runny basaltic lava
  • shield volcanoes are formed with gently sloping slides, shallow crater and a large circumference
  • they build up with no explosive activity or ejected fragments
  • e.g. Hawaii
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15
Q

how do composite volcanoes form?
what do they look like?
are they explosive?
example

A
  • most common -> formed by alternating eruptions of fragmented material followed by lava outflows/pyroclastic flow
  • has slopes of 30º near the summit and 6-10º near the base, and was layers of lava with a crater on top
  • sometimes explosive and erupts after a period of inactivity
  • e.g. Mount Etna, Italy
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16
Q

how do cinder volcanoes form?
what do they look like?
are they explosive?
example

A
  • formed by fragments of solid material which accumulate as a steep conical hill around the vent to form a cone
  • shape depends on the nature of material
  • usually concave as material spreads out near the base and has a steep angle of 30-40º
  • violent eruptions -> lava ejected into broken rocks and fragments into the atmosphere
  • e.g. Big Cinder Butte, USA
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17
Q

what are the 2 types of eruptions

A
  • lava eruption
  • pyroclastic eruptions
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18
Q

what is a lava eruptions - silica rich + example

A

when the ocean meets the continents, silica-rich sediments are absorbed and cause the lava to become more viscous. It blocks vents until enough pressure has built up to break the open.

I.e. Japan

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19
Q

what is a lava eruption - basaltic lava + example

A

Silica content in a lava eruption makes the difference between continuously erupting or those that erupt infrequently but are violent when they erupt

I.e. Hawaiian eruptions are low in silica. Runny basaltic flows down volcano sides and gases escape easily -> Involve a central vent

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20
Q

what is pyroclastic eruption - strombolian + example

A
  • explosive eruptions that produce pyroclastic flow
  • commonly marked by a white cloud of steam emitted from the crater
  • frequent gas explosions blast quantities of runny lava into the air, and when these settle and cool they form the cone of the volcano

i.e. stromboli volcano, Italy

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21
Q

what is pyroclastic eruptions - Plinian eruption

A
  • extremely violent characterised by huge clouds of pulverised rock and ash that are kilometres thick
  • gas rushes up through sticky lava and blasts ash and fragments into the sky in huge explosions
  • Gas clouds and lava can also rush down the slopes
  • part of the volcano may be blasted away during the eruption
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22
Q

what are primary hazards

A

the direct impact of an eruption i.e. lava flows, ash fallout, pyroclastic flows and gas emissions

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23
Q

what are secondary hazards

A

may be due to the way the ejected material reacts and changes i.e. ash may join with rainwater to form mudflows and create glacial flooding

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24
Q

what are the 2 types of landslides

A
  • debris avalanche
  • lahar
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25
Q

what are debris avalanches + example

A

shallow landslides, saturated with water, that travel rapidly downslope as muddy slurries. They occur around the same time as an eruption

i.e. mount st helens, USA

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26
Q

what are pyroclastic flows? + example

A

this is when ash and debris have travelled through the air and fallen to the ground. This fine ash can damage people’s lungs, it can also damage buildings as it is too heavy

i.e. Unzen Volcano, Japan

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27
Q

what is the recurrence interval or return period

A

the expected frequency of occurrence in years of an event of a particular size.
Small events occur more frequently than larger ones

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28
Q

which volcanoes erupt more frequently?

A

less explosive eruptions occur more frequently (Hawaiin), larger more explosive volcanoes erupt less often (plinian eruptions)

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29
Q

how can we predict volcano eruptions?

A
  • seismicity recording earthquakes and thermal monitoring which occur as magma rises
  • GPS - ground deformation
  • monitor gas emissions
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30
Q

how do we measure the size of the volcanic eruptions?

A
  • using the volcanic explosivity index (VEI) to describe and compare the size of volcanic eruptions
  • uses a scale from 0 (non-explosive) to 8 (explosive)
  • log scale -> increases by a factor of 10
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31
Q

what factors do the VEI use to measure the magnitude of a volcano?

A
  • the amount and height of volcanic material ejected
  • how long the eruption lasts
  • qualitative descriptive terms
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32
Q

what is the richter scale?

A

a logarithmic scale that measures the power of an earthquake. Earthquake of 5 on the Richter scale is 10 times more powerful than an earthquake of 4

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33
Q

what is the moment magnitude scale

A

measures the amount of energy released and produces figures similar to the Richter scale. For every increase of 1 of the M scale, the amount of energy released increases by over 30

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34
Q

what are the factors that the Moment magnitude scale measures

A
  • resistance of rocks
  • size of seismic waves
  • area of the fault surface broken by the earthquake
  • amount of slippage/rock movement
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35
Q

what is a hazard risk

A

when people or property are at risk

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36
Q

what causes places to be at risk from geophysical hazards

A

behavioural school of thought:
- people put themselves at risk, e.g. living at the foot of steep slopes

Structuralist school of thought:
- stresses constraints on poor people prevailing social and political system of the country
- poor people living in unsafe areas, e.g. on steep slopes of volcanoes, or on floodplains, because they are prevented from living in better areas
- there is a link between environmental hazards and underdevelopment and economic dependency in many developing countries, e.g. hurricane Katrina’s impacts were greater on the poor

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37
Q

what are the process of vulnerability

A
  • root causes (ideologies, gender norms, wealth, power, limited access to resources and structures)
  • dynamic pressures (lack of local institutions, rapid population growth)
  • unsafe conditions (dangerous locations, unprotected buildings)
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38
Q

what are the economic factors of vulnerability

A
  • levels of wealth influence the quality of housing people live in
  • many people have no option but to live in shanty towns
  • people may have less adherence to building codes and construction styles
  • poorer countries may lack the technology to warn people of upcoming natural hazards
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39
Q

what are the social factors of vulnerability

A
  • people with better education generally have higher incomes and can afford better-quality housing and vehicles
  • public education has helped reduce the number of deaths in Japan
  • awareness of hazards
  • gender: women are usually carers for children or parents and may feel responsible for them during an event
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40
Q

what are the demographic factors of vulnerability

A
  • population density: larger urban areas pose a higher hazardous risk
  • older people are more prone to risk
  • migrants may be unaware of hazards present in the country
  • people with disabilities with more vulnerable
  • cultural factors: influence public response, i.e. the extent of trust in the government
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41
Q

where is the Anak Krakatau volcano located?

A

-> this volcano is an island and caldera in the Sunda Strait (between the islands of Java and Sumatra) in the Indonesia province of Lampung
-> it lies of the Pacific Ring of Fire on the convergence of the Pacific, Eurasian and Philippine plates

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42
Q

when did Anak Krakatau erupt and what happened?

A

December 22nd 9:03 pm, 2018

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43
Q

what happened in the anak krakatau eruption?

A

> A 64-hectare chunk of the volcano slid into the ocean following the eruption. This displaced the water, pushing out waves in all directions

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44
Q

how vulnerable are the populations affected by the anak krakatau eruption?

A

-> Most people lived on the coast in remote areas, with roads that were not as navigable
-> Many had small shops and worked in local hotels, which have been destroyed
-> Lack of disaster-resistant infrastructure

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45
Q

what are the social impacts of the krakatou eruption?

A

-> 437 dead
-> 15,000 injured
-> no tsunami warning was delivered
-> 600 homes, 60 shops and 420 vessels were damaged
-> International Red Cross sent aid workers to help evacuate injured people, and bring clean water and shelters to those in need

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46
Q

what are the economic impacts of the anak krakatou eruption?

A

-> damage to coastal tourism facilities
-> damage to coastal defences, infrastructure and roads
-> damage to coastal fishing communities

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47
Q

what are the environmental impacts of the anak krakatou eruption?

A

-> coastal farming areas were inundated with salt water rendering the areas useless for agriculture
-> sea turtle populations were harmed
-> all biodiversity on anak krakatau were wiped out by the eruption

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48
Q

what are the political impacts of the anak krakatou eruption

A

-> Indonesia tsunami warning network has not been operational since 2012

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49
Q

what is the case study for a volcanic eruption in LIC

A

Anak Krakatou eruption, Indonesia

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50
Q

what is the case study for a volcanic eruption in an HIC?

A

Eyjafjallajökull Eruption 2010

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51
Q

where is the Eyjafjallajökull volcano located

A

on one of Iceland’s smaller ice caps located far south. It lies on convergence zone of both North American and Eurasian plates - constructive plate boundary

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52
Q

when did the Eyjafjallajökull volcano erupt?

A

20th march 2010

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53
Q

how did the eyjafjallajökull erupt?

A

as the volcano erupted, a 2.5km wide caldera beneath the ice cap caused the melting of a large amount of ice, leading to flooding in the south of Iceland. Volcanic ash rose 10km high, and south-easterly winds carried it to the Faroe Islands, Norway and Scotland. All explosive activity ended by the 23rd of May, however, the eruption was officially declared over on the 20th of October, 2010

54
Q

what were the social effects of the eyjafjallajökull eruption?

A
  • no fatalities were recorded
  • some reports of respiratory issues among residents
  • 500 farmers evacuated from surrounding areas
55
Q

what were the economic effects of the eyjafjallajökull eruption?

A
  • a thick ash layer had fallen on some Icelandic pastures making it wet and compact, and therefore hard to harvest or farm
  • flights were grounded to Reykjavik, disrupting the import of supplies as well as the flow of tourists
  • ash was carried into heavily used airspace over northern and central Europe
56
Q

what were the environmental effects of the eyjafjallajökull eruption?

A
  • Ash covers pasture and impacts biodiversity
  • Ash particles in the atmosphere temporarily increase levels of albedo
  • flash flood and rapid heating of river water, caused by rapidly melting ice sheet, raced downstream causing widespread damage to the river channel and banks
57
Q

what were the political effects of the eyjafjallajökull eruption?

A
  • a high proportion of flights within Europe were cancelled creating the highest levels of air travel disruption since the Second World war
  • the civil protection department was deployed to control access from vulnerable communities
58
Q

what are the volcanic hazards

A
  • jokulhlaup
  • pyroclastic flows
  • lava
  • tephra
  • ash/gas
  • lahars
59
Q

what is a jokulhlaup

A

a flood of meltwater from underneath an icecap or glacier

60
Q

what causes a jokulhlaup

A

when a volcano erupts underneath the ice and melts the ice so that it forms a lake, where it is dammed by ice, eventually, the warm water will have a great enough volume to lift the ice away. When this happens the water burst from underneath the ice, carrying with it moraines and blocks of ice

61
Q

what is an example of a jokulhlaup

A

Iceland

62
Q

What are the effects of a jokulhlaup

A
  • change the route of river channels
  • washes away bridges and roads
63
Q

what is pyroclastic flows

A

a dense mixture of superheated ejected material and poisonous gases (up to 1000ºC) moving rapidly down the sides of a composite volcano (at around 700 km/h)

64
Q

what causes pyroclastic flows

A

when a part of the volcanic cone collapses or with thick lava flow. this hazard occurs with explosive eruptions of molten or solid tephra

65
Q

what is an example of pyroclastic flows

A

Montserrat (1997)

66
Q

what are the effects of pyroclastic flows

A
  • anything in the pyroclastic flows way is destroyed
  • it leaves behind thick layers of volcanic deposits that may cause secondary hazards such as river flooding
67
Q

what is tephra

A

all types of ejected material

68
Q

what is lava

A

molten magma that has reached the earths surface

69
Q

what causes lava

A

while it is still at very high temperatures, it is in a liquid state and flows. But it depends on which volcano type and how viscous the lava will be. Basaltic = less viscous (runny), Composite = more viscous (thick)

70
Q

example of lava

A

Hawaii

71
Q

effects of lava

A

burns everything in its path -> destruction to property and human life

72
Q

what causes tephra

A

in an explosive volcanic eruption, solid and molten rock material are ejected carried by ash

73
Q

what is an example of tephra

A

Iceland

74
Q

what are the effects of tephra

A
  • falling of tephra can cause roof collapse
75
Q

what is ash

A

steam usually containing other gases escaping from geothermal active areas

76
Q

what causes the ash from volcanoes

A

geothermal active areas

77
Q

what are the effects of ash

A
  • reflect radiation from the Sun back into space, cooling the Earth
  • gases such as sulphur dioxide can mix with water to form acid rain, which may corrode infrastructure or affect vegetation
  • fluorine gas -> can contaminate farmland or water supplies
  • can cause an increase in respiratory diseases
  • Ash high in the atmosphere can disrupt the flight paths of aeroplanes because of the potential failure of jet engines
78
Q

what is an example of ash

A

Mt Pinatubo created 20 million tonnes of sulphur dioxide that rose to 32km

79
Q

what are lahars

A

water mixed with volcanic deposits flowing rapidly along existing valleys

80
Q

what causes lahars

A

caused by either heavy rainfall or through the melting of snow and ice due to the heat from an eruption at high altitude

81
Q

what is an example of a lahar

A

A lahar buried a town in Colombia from Nevado del Ruiz volcano in 1985

82
Q

what are the effects of lahars

A
  • can sweep away buildings/people because they are very fast moving
83
Q

how can we predict a volcanic eruption (7), name 3.

A
  • scientific predictions are used to provide precise statements on the time, place and size of a future event
  • effective warning systems depend of technology and communication systems and peoples ability to interpret them
  • seismometers, to record swarms of tiny earthquakes that occur as the magma rises
  • chemical sensors to measure increased suplur levels
  • Lasers/GPS to detect physical swelling of the volcano/crater
  • Ultrasound, to monitor low-frequency waves in magma resulting from a surge of gas and molten rock
  • Observations of the volcano
84
Q

are volcanoes easy to predict

A
  • earthquakes are the most difficult to predict and forecast
85
Q

what aspects of a volcanic eruption is hard to predict

A
  • the timescale (duration of eruption)
  • when the volcano will erupt
86
Q

what are the adaptations against volcanoes (3)

how can we prepare?

A
  • land use zoning: densely populated buildings (hospitals/fire services) should not be built close to fault lines or in areas at risk of landslides
  • insurance cover against hazards: however, many either cannot afford hazard insurance or find it much harder to justify spending money on an event that might not occur
  • new technology (i.e. to record the swelling of volcanoes)
87
Q

how do we manage volcanoes

A
  • drones: using drones to survey the area, minimising human damage
  • GPS monitoring: to measure ground deformation and swelling
  • Volcano diversion: the diversion of roads away from active areas or over them in the form of bridges
88
Q

what are the 3R’s and what do they stand for?

A

These are the short-term, mid-term and long-term responses after an event
- rescue: saving people so they can survive despite having only minimum life necessites (saving people, getting water, etc)
- rehabilitation: restoring the function of public services, a process that takes place over 1 or 2 years
- reconstruction: rebuiling the public system, economic system, infrastructure and governance functions -> predicted to take 2 to 5 years

89
Q

what is the focus of an earthquake

A

point at which the plates release their tension or compression suddenly

90
Q

what is the epicentre of an earthquake

A

marks the point on the surface of the Earth immediately above the focus of the earthquake

91
Q

what is worse: a deeper or shallow epicentre

A

a shallower ones because the seismis waves have to travel a shorter distance to get to the surface, whereas, the seismic waves from a deeper earthquake can be absorbed by the rock above it

92
Q

What is a shallow focus/earthquake

A
  • Occurs relatively close to the ground surface
  • Greater potential to do damage as less of the energy released by the earthquake is absorbed by overlying material.
93
Q

What is a deep focus/earthquake

A

Occur at the considerable depth under the ground
- Travel further to reach the ground, more enrgy absorbed so less impact

94
Q

What are the different waves we experience in a earthquake?

A

P waves (primary)
S waves (secondary)
L waves (surface love)
Rayleigh waves

95
Q

What are primary waves (p -waves)

A
  • Compressional waves: vibrates in the direction they are travelling (longitudinal)
  • Fastest moving waves and reach surface FIRST
  • Travel through both solids and liquids
  • Only damaging in the most powerful earthquakes
96
Q

What are secondary waves (s-waves)

A

Move in a sideways motion at 90 degress to the direction of travel (transverse)
- Slower than p waves and are 60% of the speed of p - waves
- ONLY travel through solids
- Do more damage than p - waves

97
Q

What are surface love waves (L waves)

A

Slowest waves that cause the most damage as they travel near the surface
- Come shake the ground at right angles to the direction of the wave and some have a rolling motion that produces vertical ground movement.

98
Q

What are rayleigh waves?

A

Cause the ground to move up and down
- Travel slowly through the crust and cause the msot damage along with surface love waves

99
Q

How do earthquakes occur at a plate boundary?

A
  • As oceanic crust slides into hotter fluid mantle, it takes time to warm up. As slab descends, pressure builds up and increase stress on rocks which then distort and cracks, relaesing energy eventually creating earthquakes
100
Q

Why do some earthquakes occur so deep?

A

Subduction is relatively fast so by the time crust has cracked it has slid several hunred kilometers into the mantle so earthquakes occurs deeper

101
Q

What does the size of the earthquake depend on?

A
  • Thickness of the descending slab
  • Rate of movement
102
Q

What is a constructive plate boundary?
Can earthquakes occur there?
Are they powerful?

A
  • Plates move away
  • Yes due to moving of plates
  • Not very powerful due to no subduction zones
103
Q

What is a destructive plate boundary?
Can earthquakes occur there?
Are they powerful?

A
  • Plates collide
  • Yes due to subduction of oceanic plate
  • Very powerful due to quicker subduction
104
Q

What is a conservative plate boundary?
Can earthquakes occur there?
Are they poweful?

A
  • Plates slide past each other
  • Yes due to tension build up
  • Can be explosive to release of pressure and energy
105
Q

What are some human triggers of earthquakes

A

Construction of large dams
Fracking and mining
Testing of nuclear weapons

106
Q

How has the construction of large dams triggered earthquakes

A
  • Due to increased load on previously stable land
    e.g. Colorado river was dammed by the Hooover dam and the increased load of water reactivated long-dormant faults int he area causng 6000 minor ewarthquakes over the next 10 years, though none casued damage
107
Q

How has fracking triggered earthquakes

A
  • A process where water containing certain chemicals is injected at very high pressure into rocks inorder to open them up and release natural gas withing ht rocks. In 2011, fracking led to a 2.3 magnitude earthquake in Lancashire, UK.
    Biggest one was in Canada of 4.4 magnitude, fracking earthquakes rarely cause damage and arent really felt by people
108
Q

How has testing of nuclear weapons triggered earthquakes

A
  • Underground nuclear testing e.g. since 1966, France has carried out over 80 underground nuclear explosion tests on the Polynesian isalnd of Moruroa, where more than 120,000 people live. In 1966, a 120,000 tonne nuclear device was detonated, producing radioactive fallout.
109
Q

what is disaster risk

A

expressed as the likelihood of loss of life, injury or destruction and damage froma disaster in a given period of time. It is recognised as a consequence of interactions between a hazard and characteristics that amke people and places vulnerable and exposed

110
Q

what factors might affect disaster risk

name 3

A
  • construction
  • urban planning
  • education
  • disaster risk management
  • increasing population means increased exposure
  • high levels of inequality
111
Q

what is the LIC case study for earthquakes

A

Haiti 2010

112
Q

what and why was the magnitude so great and what was the cause of the 2010 haiti earthquake

A

magnitude: richter 7 -> the earthquake had a shallow depth
cause: caused by the rupture of the Enriquillo-Plantain Garden fault, which had been locked for 250 years, gathering stress

113
Q

name 3 social effects of the haitian earthquake

A
  • 1.3 million people made hoemless due to collapsed or unsafe housing
  • 300,000 injured, where treatment is difficult due to several hospitals collapsing
  • 222,000 deaths caused by collapsing buildings, a small tsunami and the cholera epidemic in the preceeding weeks
114
Q

name 3 economic impacts of the haitian 2010 earthquake

A
  • airport and port damage = decrease in imports and exports as well as a slowdown in the rescue and response from overseas
  • businesses destroyed and vast sums of moeny for the rebuilding process - money that Haiti did not have
  • 30,000 commercial building collapsed leading to a loss of trade for an already crippled economy
115
Q

what are the 3 environmental impacts of the Haiti earthquake

A
  • deforestation and forest clearance to make way for temporary camps
  • small scale pollution by the leakage of oil, due to the rupture and damage to industrial facilities
  • pollution of water supply = cholera epidemic
116
Q

what are 2 political impacts of the haiti earthquake

A
  • appeals for aid were immediately requested, but the American red cross quickly ran out of supplies and turned to public food donations
  • Haiti’s justics system became a disarray, with very few people being able to be processed and arrested or brought infront of a judge at all
117
Q

how does the population density link to the location of the epicentre of the earthquake

A
  • the epicentre was located closest in the Port au Prince region, where most of the population is located -> 300,000 people were affected by this most extreme area, and 2 million affected in violent shaking areas
118
Q

how has haitis building design and distribution have increased levels of vulnerability

A

haitis crowded buildings and poor earthquake-proof infrastructure, is a major afctor that caused the collapsing of multiple house and residential areas

119
Q

what does haiti need to do now to help restore its society? and what are the domicans scared is going to happen?

A

Rebuilding Haiti’s homes, schools, roads and
other infrastructure will take between $8 billion
and $14 billion. Many Dominicans fear a ood
of illegal migrants into their country due to the
poverty in Haiti unless reconstruction is swift and
effective.

120
Q

what is the HIC case study for earthquakes

A

Alaska (USA) - 2018

121
Q

what caused the alaskan 2018 earthquake?

A

when the pacific plate subducted beneath the north ameriacn plate, converging at a rate of 57mm per year

122
Q

name 3 social effects of the 2018 alaskan earthquake

A
  • no fatalities reported
  • several damage to buidlings and houses
  • 46,000 people were left without electricity
123
Q
A
123
Q
A
123
Q
A
124
Q

name 3 economic impacts of the 2018 alaskan earthquake

A
  • trans alaskan oil pipeline temporarily shut down the flow of oil
  • $30 million damages to Anchorage (city)
  • $25-$50 million damages to school district
125
Q

name 2 environmental impacts of the alaskan earthquake

A
  • liquefaction occured in some areas (liquefaction occurs when the shaking causes loose or sturated soils to lose their strength, causing them to act like a liquid rather than a solid. This can result in significant damage to buildings and infrastructure)
  • no oil leaks from pipeline
126
Q

name 1 political impact of the 2018 alaskan earthquake

A
  • Anchorage mayor declared a state of emergency for his city, requested both state and federal assistance
127
Q

what is the distribution of population density in Alaska

A
  • mean population of 12-133 people per square area in the south of Alaska
128
Q

what is the relationship between the epicentre of the alaskan earthquake and the population density of the country

A
  • the shallow epicentre is located in Anchorage as well as the largest mean number of people per square mile
129
Q

what are the additional risks to coastal communities in this areas (Alaksa) strong ‘megathrust’ earthquakes

A

Some parts of the coast are a lot more vulnerable to tsunami inundation (tsunami flooding) than others, and citizens in these locations will have to move to higher ground extremely rapidly once the earthquake waves subside.

130
Q

what is a megathrust earthquake?

A
  • earthquakes that occur at covergengent plate boundaries, where one tectonic plate is forced underneath one another
131
Q

what do the alaskan officials say to due before, during and after an earthquake

A
  • before: complete your disaster mitigation (disaster supply kit, turning off gas, electricty and water, etc)
  • during: drop-cover-hold on, drive away from underpass and bridges
  • after: check for injuries and evacuate from collapsed buildings

Geography (10 decks)

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