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 oceanic crust
- underneath is a 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
2
Q
what is the asthenosphere?
A
the layer underneath the lithosphere
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
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 Earths interior
- Primordial heat -> the heat lost by the Earth as it continues
to cool from its original formation
5
Q
what are the 3 mechanisms related to plate movement?
A
- subduction
- plumes
- hotspots
5
Q
how to convection currents operate
A
Heat from the core makes magma in the mantle rise towards the crust. As the hot current nears the crust, it begins to cool and sink back towards the core. As the magma sinks, it drags the plates across the surface of the Earth
6
Q
what is subduction?
A
subduction refers to the plunging of one plate below another
7
Q
what is the process of subduction
A
- oceanic lithosphere plates collide with another plate - whether is continental or oceanic
- The oceanic plate is a lot denser than the continental
- the subducting plate is forced to subduct and creates a subduction zone
8
Q
what is a plume?
A
a column of hot volcanic ash, gases, and debris ejected into the atmosphere during an explosive volcanic eruption
9
Q
what is rifting?
A
Rifting occurs at diverging 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.
10
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
11
Q
where in the world are volcanoes distributed?
A
most around the Pacific Ring of fire
12
Q
what are the 3 different types of volcanoes?
A
- shield
- composite
- cinder
13
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
14
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, lava outflows/pyroclastic flow
- has slopes of 30º near the summit and 6-10º near the base
- explosive and erupts after a period of inactivity
- e.g. Mount Etna, Italy
15
Q
how do cinder volcanoes form?/ on which type of plate boundary
what do they look like?
are they explosive?
example
A
- formed by fragments of solid material which accumulate around the vent to form a cone, usually around convergent plate boundaries
- 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 ejects broken rocks and fragments into the atmosphere
- e.g. Big Cinder Butte, USA
16
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
17
Q
what is a lava eruption - basaltic lava + example
A
Basaltic magmas have lower viscosities, higher temperatures, and lower volatile contents therefore generally have a lower potential for explosive activity. However, basaltic eruptions display great variability, from mild lava flows to more energetic explosions with large plumes
I.e. Hawaiian eruptions are low in silica. Runny basaltic flows down volcano sides and gases escape easily
18
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
i.e. stromboli volcano, Italy
19
Q
what is a Plinian eruption
A
extremely explosive eruptions, producing ash columns that extend many tens of miles into the stratosphere and that spread out into an umbrella shape. These large eruptions produce widespread deposits of fallout ash. Eruption columns may also collapse due to density to form thick pyroclastic flows
20
Q
what are primary hazards
A
the direct impact of an eruption i.e. lava flows, ash fallout, pyroclastic flows and gas emissions
21
Q
what are secondary hazards + what are the secondary hazards of volcanoes
A
indirect effects caused by the primary impacts, after the main event - in the coming hours, days and weeks
- lahars
- acid rain
22
Q
what are the 2 types of volacnic landslides
A
- debris avalanche
- lahar
23
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
24
what are pyroclastic flows? + example
a dense, fast-moving flow of solidified lava pieces (1000ºC at around 700km/h), volcanic ash, and hot gases down a composite volcano. This hot ash can damage people’s lungs and also damage buildings as it is too heavy
i.e. Unzen Volcano, Japan
25
what is the recurrence interval or return period
the expected frequency of occurrence in years of an event of a particular size.
Small events occur more frequently than larger ones
26
which volcanoes erupt more frequently?
less explosive eruptions occur more frequently (Hawaiin), larger more explosive volcanoes erupt less often (plinian eruptions)
27
how do we measure the size of the volcanic eruptions?
- 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
28
what factors do the VEI use to measure the magnitude of a volcano?
- the amount and height of volcanic material ejected
- how long the eruption lasts
- qualitative descriptive terms
29
what is the richter scale?
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
30
what is the moment magnitude scale
measures the amount of energy released by an earthquake 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
31
what are the factors that the Moment magnitude scale measures
- resistance of rocks
- size of seismic waves
- area of the fault surface broken by the earthquake
- amount of slippage/rock movement
32
what is a hazard risk
when people or property are at risk
33
what are the 2 human schools of thought that cause places to be at risk from geophysical hazards + explain them
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 in many developing countries, e.g. hurricane Katrina’s impacts were greater on the poor
34
what are the 3 causes of vulnerability
- 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)
35
what are the economic factors of vulnerability
- 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
36
what are the social factors of vulnerability
- 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
37
what are the demographic factors of vulnerability
- 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
38
where is the Anak Krakatau volcano located?
-> in the Indonesia province of Lampung
-> it lies of the Pacific Ring of Fire on the convergence of the Pacific, Eurasian and Philippine plates
39
when did Anak Krakatau erupt?
December 22nd 9:03 pm, 2018
40
what happened in the anak krakatau eruption?
> A 64-hectare chunk of the volcano slid into the ocean following the eruption. This displaced the water, pushing out 5m waves in all directions
41
how vulnerable are the populations affected by the anak krakatau eruption?
-> 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
42
what are the social impacts of the krakatou eruption?
-> 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
43
what are the economic impacts of the anak krakatou eruption?
-> damage to coastal tourism facilities
-> damage to coastal defences, infrastructure and roads
-> damage to coastal fishing communities
44
what are the environmental impacts of the anak krakatou eruption?
-> 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
45
what are the political impacts of the anak krakatou eruption
-> Indonesia tsunami warning network has not been operational since 2012
46
what is the case study for a volcanic eruption in LIC
Anak Krakatou eruption, Indonesia
47
what is the case study for a volcanic eruption in an HIC?
Eyjafjallajökull Eruption 2010
48
where is the Eyjafjallajökull volcano located
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
49
when did the Eyjafjallajökull volcano erupt?
20th march 2010
50
what happened when the eyjafjallajökull volcano erupted? when did the explosive activity and the eruption declared over?
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
51
what were the social effects of the eyjafjallajökull eruption?
- no fatalities were recorded
- some reports of respiratory issues among residents
- 500 farmers evacuated from surrounding areas
52
what were the economic effects of the eyjafjallajökull eruption?
- 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
53
what were the environmental effects of the eyjafjallajökull eruption?
- Ash covers pasture and impacts biodiversity
- Ash particles in the atmosphere temporarily increase levels of albedo
- jokulhlaups caused increase flooding in southeatern iceland
54
what were the political effects of the eyjafjallajökull eruption?
A number of world leaders and politicians had to postpone planned trips or were diverted and delayed due to the closure of airports and airspace: Prime Minister of Russia, Vladimir Putin postponed a trip to Murmansk on 15 April.
55
what are the volcanic hazards
- jokulhlaup
- pyroclastic flows
- lava
- tephra
- ash/gas
- lahars
56
what is a jokulhlaup
a flood of meltwater from underneath an icecap or glacier
57
what causes a jokulhlaup
When a subglacial volcano erupts, the intense heat rapidly melts ice, creating a reservoir of meltwater. Once the pressure becomes too high, the water bursts out, often causing catastrophic flooding.
58
what is an example of a jokulhlaup
Iceland
59
What are the effects of a jokulhlaup
- change the route of river channels
- washes away bridges and roads
60
what causes pyroclastic flows
When a volcano explosively erupts, it can produce a tall column of hot gas and ash. If this column becomes too dense or loses upward momentum, it collapses under gravity, sending pyroclastic material rushing down the volcano’s slopes.
61
what is an example of pyroclastic flows
Montserrat (1997)
62
what are the effects of pyroclastic flows
- anything in the pyroclastic flows way is destroyed
- Their speed makes them nearly impossible to outrun.
- They can travel across water and even climb over ridges.
- The fine ash they leave behind can harden into solid rock, burying landscapes.
63
what is tephra
all types of ejected material
64
what is lava
molten magma that has reached the earths surface
65
what causes lava
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)
66
effects of lava
burns everything in its path -> destruction to property and human life
67
what causes tephra
in an explosive volcanic eruption, solid and molten rock material are ejected carried by ash
68
what is an example of tephra
Iceland
69
what are the effects of tephra
- falling of tephra can cause roof collapse
70
what is ash
steam usually containing other gases escaping from geothermal active areas
71
what causes the ash from volcanoes
geothermal active areas
72
what are the effects of ash
- 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
- 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
73
what is a place that demonstrates a example of ash from volcanoes
Mt Pinatubo created 20 million tonnes of sulphur dioxide that rose to 32km
74
what are lahars
fast-moving mudflows, primarily composed of volcanic ash and debris mixed with water, that originate from volcanoes
75
what causes lahars
caused by either heavy rainfall or through the melting of snow and ice due to the heat from an eruption at high altitude
76
what is an example of a lahar
A lahar buried a town in Colombia from Nevado del Ruiz volcano in 1985
77
what are the effects of lahars
- can sweep away buildings/people because they are very fast moving
78
how can we predict a volcanic eruption (4)
- seismometers, to record swarms of tiny earthquakes that occur as the magma rises
- Lasers/GPS to detect physical swelling of the volcano/crater
- Ultrasound, to monitor low-frequency waves in magma
- Observations of the volcano -> i.e. monitoring gas emissions
79
are volcanoes easy to predict
- earthquakes are the most difficult to predict and forecast
80
what aspects of a volcanic eruption is hard to predict
- the timescale (duration of eruption)
- when the volcano will erupt
81
what are the adaptations against volcanoes (4)
| how can we prepare?
- 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)
- drones: using drones to survey the area, and map the most vulnerbale areas
82
what are the 3R's and what do they stand for?
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
83
what is the focus of an earthquake
point at which the plates release their tension or compress suddenly
84
what is the epicentre of an earthquake
marks the point on the surface of the Earth immediately above the focus of the earthquake
85
what is worse: a deeper or shallow epicentre
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
86
What is a shallow focus/earthquake
- 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.
87
What is a deep focus/earthquake
Occur at the considerable depth under the ground
- Travel further to reach the ground, more enrgy absorbed so less impact
88
What are the different waves we experience in a earthquake?
P waves (primary)
S waves (secondary)
L waves (love waves)
Rayleigh waves
89
What are primary waves (p -waves)
- 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
90
What are secondary waves (s-waves)
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
91
What are surface love waves (L waves)
Slowest waves that cause the most damage as they travel near the surface
- they shake the ground at right angles to the direction of the wave and some have a rolling motion that produces vertical ground movement.
92
What are rayleigh waves?
Cause the ground to move up and down
- Travel slowly through the crust and cause the msot damage along with surface love waves
93
How do earthquakes occur at a plate boundary?
As the plates move past each other, they sometimes get caught and pressure builds up. When the plates finally give and slip due to the increased pressure, energy is released as seismic waves, causing the ground to shake. This is an earthquake.
94
Why do some earthquakes occur so deep?
Earthquakes that occur due to subduction are relatively fast - by the time crust has cracked it due to the mantles heat the plate has slid several hundred kilometers into the mantle so earthquakes occurs deeper
95
What does the size of the earthquake depend on?
- Thickness of the rock slab
- Rate of movement
96
What is a constructive plate boundary?
Can earthquakes / volcanoes occur there?
Are they powerful?
- Plates move away
- Yes due to moving of plates / shield volcanoes form
- Not very powerful due to no subduction zones
97
What is a destructive plate boundary?
Can earthquakes /volcanoes occur there?
Are they powerful?
- Plates collide
- Yes due to subduction of oceanic plate / composite volcaoes form
- Very powerful due to quicker subduction
98
What is a conservative plate boundary?
Can earthquakes / volcanoes occur there?
Are they poweful?
- Plates slide past each other
- Yes due to tension build up/ no volcanoes are formed
- Can be explosive to release of pressure and energy
99
What are some human triggers of earthquakes
Construction of large dams
Fracking and mining
Testing of nuclear weapons
100
How has the construction of large dams triggered earthquakes
- 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
101
How has fracking triggered earthquakes
- A process where water containing certain chemicals is injected at very high pressure into rocks to open them up and release natural gas within hot rocks.
In 2011, fracking led to a 2.3 magnitude earthquake in Lancashire, UK.
The biggest one was in Canada, with a magnitude of 4.4. Fracking earthquakes rarely cause damage and aren’t really felt by people
102
How has testing of nuclear weapons triggered earthquakes
- The intense heat and pressure of the explosion vaporize rock, creating cavities and fracturing the surrounding material, including nearby faults. e.g. North Korea's 2017 nuclear test produced a magnitude 6.3 earthquake and subsequent aftershocks
103
what is disaster risk
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 the capacity for a community to cope that makes people and places vulnerable and exposed
104
what human factors might affect disaster risk
| name 3
- construction
- urban planning
- education
- disaster risk management
- increasing population means increased exposure
- high levels of inequality
105
what is the LIC case study for earthquakes
Haiti 2010
106
what and why was the magnitude of the 2010 haiti earthquake so great and what was the cause of it
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
107
name 3 social effects of the haitian earthquake
- 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
108
name 3 economic impacts of the haitian 2010 earthquake
- 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
109
what are the 3 environmental impacts of the Haiti earthquake
- 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
110
what are 2 political impacts of the haiti earthquake
- 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
111
how does the population density of Haiti link to the location of the epicentre of the earthquake
- the epicentre was located closest in the Port au Prince region, where most of the population is located -> 300,000 people were affected
112
how has haitis building design and distribution have increased levels of vulnerability
haitis crowded buildings and poor earthquake-proof infrastructure, is a major afctor that caused the collapsing of multiple house and residential areas
113
what does Haiti need to do now to help restore its society? and what are the Dominicans scared is going to happen?
Rebuilding Haiti’s homes, schools, roads and other infrastructure will take between $8 billion and $14 billion. Many Dominicans fear a flood of migrants into their country due to the
poverty in Haiti unless reconstruction is swift and effective.
114
what is the HIC case study for earthquakes + magnitude
Alaska (USA) - 2018 + richter 7
115
what caused the alaskan 2018 earthquake?
when the pacific plate subducted beneath the north ameriacn plate, converging at a rate of 57mm per year
116
name 3 social effects of the 2018 alaskan earthquake
- no fatalities reported
- several damage to buidlings and houses
- 46,000 people were left without electricity
117
name 3 economic impacts of the 2018 alaskan earthquake
- trans alaskan oil pipeline temporarily shut down the flow of oil
- $30 million damages to Anchorage (city)
- $25-$50 million damages to school district
117
name 2 environmental impacts of the alaskan earthquake
- 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
117
name 1 political impact of the 2018 alaskan earthquake
- Anchorage mayor declared a state of emergency for his city, requested both state and federal assistance
118
what is the distribution of population density in Alaska
- mean population of 12-133 people per square mile in the south of Alaska
119
what is the relationship between the epicentre of the alaskan earthquake and the population density of the country
- the shallow epicentre is located in Anchorage as well as the largest mean number of people per square mile
120
what are the additional risks to coastal communities in Alaksa from strong 'megathrust' earthquakes
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.
121
what is a megathrust earthquake?
- earthquakes that occur at destructive plate boundaries, where one tectonic plate is forced underneath one another
122
what do the alaskan officials say to due before, during and after an earthquake
- before: complete your disaster mitigation (disaster supply kit, turning off gas, electricity and water, etc)
- during: drop-cover-hold on, drive away from underpass and bridges
- after: check for injuries and evacuate from collapsed buildings
123
what 3 geomorphological hazards can earthquakes create
- tsunamis
- liquefaction
- landslides
124
where are the disaster risk of earthquakes highest + named and explained example
- where people are not educated on preparation techniques and where buildings are not earthquake-resistant
- i.e. in Cairo (1992), many poorer people in villages and inner city slums were killed and injured when their mud-walled houses collapsed. Similarly, richer people were killed by collapsing concrete buildings - that were sometimes built without planning permission
125
how do we predict earthquakes?
- scientific predictions are used to provide precise statements on the time, place and size of the future event
- forecasts
126
how do we prepare for earthquakes
- better forecasting and warning
- improved building design and location
- establishing emergency procedures
127
how to monitor earthquakes. Name 3:
- changes in rock stress
- anomalies in the earth’s magnetic field
- using seismometers to measure seismic waves
128
what is the seismic gap theory
- it states that over a prolonged period of time, all parts of a plate boundary must move by almost the same amount
- so if 1 part has not moved and the others have, then the part that hasn’t moved is likely to move next
129
why are the oarfish important to predicting earthquakes
- In Japanese folklore, the oarfish are the messengers of earthquakes. When an earthquake is intended to occur, dead oarfish wash up on beaches. This is because earthquakes release carbon monoxide that kills deep-sea creatures like oarfish.
130
How can we reduce the impact of earthquakes (4)
- land-use zoning
- improving building design
- improving early warning systems
- educating the public and raisimg awareness about what to do
131
examples of earthquake-vulnerable structures and why they are bad
- vertical rods -> do not allow movement during earthquake = bad
- inflexible joints in pipes = usually carry gas or sewage and can break during an earthquake
- Bay bridge = upper structures can collapse easily onto lower bridge structures
132
examples of earthquake-resistant structures and why they are good
- golden gate bridge = can sway with earthquakes
- Flexible joints in pipes = less prone to breakage during earthquake
- structure with spiral rods = stronger structure against earthquakes
133
what are some methods to create earthquake-resistant housing in LICs (3)
- Light walls and gables -> Lightweight structures are subject to smaller forces and are less likely to fall during earthquakes
- Reinforced walls -> Natural materials (bamboo/eucalyptus) have been reinforced with plastic mesh to prevent collapse
- cheap shock absorbers -> made with tyres filled with sand and fastened between floor and foundation
134
how can we control earthquakes
- We can alter the fluid pressure deep underground at the point of greatest stress in the fault line, where a series of small and less damaging earthquake events may be triggered. This could release energy that would otherwise be built up
- A series of controlled underground nuclear explosions might relieve stress before it reaches critical levels
135
How do we control tsunamis
- generally managed through sea walls
- and early-warning systems
136
what is a disadvantage of seas walls for tsunami control
- Walls can only provide a certain amount of protection and will not stop bigger waves
- cost constraints dictate the height of the wall that can be built
137
what is a megadisaster
an event that kills more than 100,000 people
138
what type of disaster cause the greatest deaths and which one affects most people
- earthquakes cause the greatest deaths (750,000)
- Flooding affects most people (2.4 billion)
139
what type of disaster occurs most regularly
- flooding
- storms
140
which geophysical hazard affects most people
Earthquakes and tsunamis
141
What is the percentage of death difference between HIC and LIC
- HIC: 13% deaths
- LIC: 33% deaths
20% difference in deaths, where many of disasters are less prevalent in LICs, evidencing how much they were impacted by disasters
142
What aspects affect the frequency and intensity of disastrous events?
- increasing population
- increasing urbanisation -> more urban places are being built that expand onto fault lines, such as in Tehran (a megacity built on an active fault line)
- Vulnerable areas -> building on places that are more earthquake unstable
- environmental degradation (destruction of mangrove swamps in Sri Lanka = increased vulnerability of coastal communities to the 2004 tsunami)
143
what is mass movement
the movement down slope of any weathered material at a range of speeds, resulting in a destruction of property and/or loss of life, and is often triggered by human activity
144
what can cause mass movements (6)
-> angle of the slope
-> nature of the material (strength of the material compared to the force acting on it)
-> amount and type of vegetation
-> water (rainfall)
-> human activity (deforestation destabilises the ground)
-> climate
145
what are the 2 key effects of gravity on downslope movement
1. move material downslope
2. Acts to stick the particles to the slope
146
how does water affect mass movement
Water lubricates particles and might fill spaces between the particles, therefore reducing friction with the material and the slope and increasing the risk of mass movements
147
how does pore pressure affect mass movement
it will greatly increase the ability of the material to move because it reduces the materials sheer strength
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What causes slope failure (the slope falling and crumbling)?
- reduction in internal resistance or shear strength (the strength to resist the downward movement of the slope) of the slope
- increase in shear stress -> the forces attempting to pull a mass downslope
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what is soil creep
a slow downward progression of rock and soil down a low-grade slope
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what are the fastest mass movements, and why
mudflows because they are the wettest mass movement
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what are the slowest mass movements
Soil creeps -> They are the driest mass movements
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Where are landslides located? (5)
-> fairly scattered
- -> can be located around plate margins and active tectonic processes, i.e. the Himalayas (when the plates buck up to form these mountain ranges, they hold tension which can create fatal landslides)
-> high levels of precipitation
- -> high population density
-> low-income countries where the mitigation schemes are less likely to be in place
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what are the causes of landslides in Nepal in 2015 (not a proper case study, just an example) (3) + name one major 2015 landslides
- seasonal rainfall
- previous slides weaken slopes
- road construction
- an ice and rock avalanche at Langtang triggered by the 2015 Gorkha earthquake
154
What are the impacts of the 2015 Nepal landslides (not a proper case study, just an example) (3)
- substantial loss of life
- entire settlements were buried
- The valley below was severely obstructed and covered by debris
155
what is the LIC case study for landslides + is it fast or slow moving?
Freetown, Sierra Leone + fast-flowing (mnemonic: “freetown = fast, F and F)
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what is the HIC case study for landslides + is it fast or slow moving
Panzano Landslides, Italy + slow moving (mnemonic: :”Panzano = slow -> kinda rhymes”)
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what happened in Freetown, Sierra leone? case study
- a hillslide collapsed on Monday at 6am, causing a mudslide on the outskirts of Sierra Leone’s Capital, Freetown
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causes of Freetown’s mudslides? case study
- mudslide occurred after 3 days of torrential rain
- The construction of large homes in hillside areas and unrestricted deforestation for residential purposes weakened the stability of nearby slopes and caused soil erosion
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what did they do to help people trapped in the freetown mudlsides
- military personnel have been deployed to help rescue those still trapped
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Name 3 facts about Freetown, Sierra leone
- 60% of the population is living in poverty
- Freetown is Sierra Leone’s major urban, economic, educational, political and cultural centre
- it has a population of about 1 million
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when did the mudslide in Freetown occur
- 14th August 2017
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social affects of the Freetown mudslides (4)
- 1141 people still missing
- damage to hundreds of home
- 3000 people left homeless and moved to emergency camps
- unsanitary water raosed fears of cholera
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economic impacts of the Freetown mudslides (2)
- power outages in many communities caused by deliberate cutting off of supplies in order to avoid electrical accidents
- roads and bridges are washed away = $1 million in damages
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Environmental impacts of the freetown mudslide (3)
- loss of biodiversity
- loss of agricultural productivity
- changes to river drainage patterns of the surrounding areas
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Political impacts of Freetown landslide (4)
- Sierra Leone’s president declaring a state of national emergency and announcing a relief centre in Regent
- Aid donations from China, UK, Spain and Ireland
- The world food programme provided rations for 7500 people
- the EU authorised €300,000 of humanitarian aid
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Where and when did the Panzano landslides occur + what is teh overall population
- Panzano is a small village found in the Abruzzo region of southern italy with a population of 200
- 12th Feb 2017
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name 3 facts about Italy (Panzano case study)
- 2% of population living in poverty
- literacy rate = 99%
- life expectancy = 83 years
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why did the Panzano landslide occur (2)
- 2 metres of snow melted due to an increase in temperature, meaning that there was direction saturation of the slope
- Intense rainfalls were recorded between the 6th and 10th of February.
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social impacts of panzano landslide (3)
- more than 100 people have been evacuated and are staying at local hotels or with family and friends
- several buildings have collapsed and sustained damage
- no deaths
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economic impatcs of panzano landslide (1)
- losses to 35 properties
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environmental impacts of panzano landslide (1)
- agricultural area surrounding the village deemed unsafe due to the possibility of further movement
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political impacts of the panzano landslide (2)
- Italy’s civil protection department has set up monitors in the village to track movement
- the local health authority has also sent a team of psychologists to assist evacuated people
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What are the ways to manage landslides? (4)
- terracing of steep slopes and making them more secure
- Restraining structures: gabions and stone walls to trap failed material behind the structure and not let it fall on roads
- Improve drainage systems to reduce the build-up of water in slopes and therefore making them less likely to fall
- erosion control: rock armour will minimise the forces acting at the base of the cliffs
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factors affecting the impacts of geophysical events (8)
- magnitude and frequency of event
- population density
- type of buildings
- time of day
- distance from event
- types of rocks and sediments
- economic development
- secondary hazards
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economic factors affecting peoples vulnerability to geophysical events
- levels of wealth and development influences the quality of housing that people live in, i.e. poorer populations have no option but to live in shanty towns
- Construction styles and building codes
- access to technology: Earthquake and tsunami warnings are issued to people via smartphones
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what are the social reasons that affects people vulnerability to geophysical events
- education levels
- People may want to live in riskier areas mainly because of culture/ that is where their family has lived for years
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What are short-term responses
immediate response scenarios:
- find and rescue people
- using thermal sensors and sniffer dogs to find people
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what are mid-term responses
- rehabilitation: making peoples home safe and for people to live in them again
- i.e. during UK floods 2007, some people were unable to return back to their homes after a year
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What are long-term responses
- Rebuilding and reconstruction
- calling for aid from other countries to reduce the risk of future impacts
- building new defences, e.g. the Wivenhoe Dam in Queensland Australia
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following the Indonesian tsunami 2004, what were the rescue services
- immediately helping disaster survivors
- immediately burying the victims’ dead bodies
- immediately enhancing basic facilities and infrastructure to be able to provide adequate services for the victims
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Following the Haiti earthquake (and storm), what were the post-disaster steps
- rescue: rescue trapped people, clear rubble, and restore water and sanitation to prevent disease with the help of NGOs to determine the extent of the devastation
- Rehabilitation: 3 million people needed to be rehoused, and infrastructure needed to be rebuilt. One of the world’s most aid-dependent states due to deep corruption and civil mistrust = which means money is scarce
- Reconstruction: Many countries have set up reconstruction programmes in Haiti, and government agencies were set up exclusively to manage the reconstruction, but reconstruction will take decades
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How can we use phones to aid natural disasters
- using phones for hazard mapping
- using phones to track missing children
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what are the issues of using phones to aid in natural disasters (3)
- Phone batteries do not last all day to guarantee all people receive warnings
- all models and companies of phones may not be supported by the warning system
- not everyone always has their phones on them
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what is rapidFTR?
an open-source app designed to reunite children with their families in rapidly developing disaster situations. The faster the children are found, the less vulnerable they are to violence, exploitation and trafficking
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what is an adv of rapidFTR?
- Because it is open source, it can be used and adapted by different teams for a range of uses ,i.e. can track women at risk of violence
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How are phones used for hazard mapping?
- Communication technologies allow information about geophysical hazards to spread quickly. UNICEF, in Rio, has been training young people to alert the authorities about natural hazards in their home region to initiate a response
