Hazards Flashcards
1
Q
What is a hazard
A
An extreme event that threatens people, their property and settlements
2
Q
When does a hazard become a disaster
A
When the hazard causes widespread destruction to property and human lives i.e deaths
3
Q
What is the determine of a disaster demonstrated by
A
Degg’s model venn diagram
4
Q
How hazardous or disastrous an event also depends on:
A
- Risk; the probability of an event happening and the scale of its possible damage
- The ability of a population to take preventative or precautionary measures, known as adjustment or mitigation, and their ability to cope
- How easy the hazard events are to predict
- The frequency of events
- Some places may experience more than one type of hazard (hazard hot spot e.g. Philippines or California)
- The severity of the hazard
5
Q
What is the hazard categorisation
A
- Geological (e.g. volcanic eruptions, earthquakes)
- Climatic (e.g. tropical storms)
- Biological
- Technical
6
Q
What is the earth’s structure
A
Inner core —> Outer core —> Mantle —> Core
7
Q
What is the structure of the inner core
A
- 1270km thick
- Solid —> iron and nickel
- 3000°C
8
Q
What is the structure of the outer core
A
- 2200 km thick
- Liquid
- 3000°C
9
Q
What is the structure of the mantle
A
- 2900 km thick
- Solid, but flows (rheological consistency)
- 375°C
10
Q
What is the structure of the crust
A
- 0-70km thick
- Continental and Oceanic crust
- Solid —> granite and basalt
- 10°C
11
Q
What are the two types of crust
A
Oceanic and Continental
12
Q
What is Oceanic crust
A
- Newer (less than 200 million years old)
- Denser (heavier)
- Thinner —> 5km
- Can subduct
13
Q
What is Continental crust
A
- Older (1500 million years old)
- Less dense
- Thick —> 30km
- Can’t subduct
14
Q
What does Lithosphere mean
A
Top 100km of the earth (i.e. crust and top part of the mantle) that makes up the earth’s tectonic plates
15
Q
What does Asthenosphere mean
A
The rest of the upper part of the mantle that acts as a lubricant for the tectonic plates to move on
16
Q
How do tectonic plates move
A
- Slab pull
- Ridge push
- Convection currents
17
Q
What is slab pull
A
The denser plate sinks back into the mantle under the influence of gravity. It pulls the rest of the plate along behind it
18
Q
What is ridge push
A
Magma rises as the plates move apart, the magma cools to form new plate material and as it cools it becomes denser and slides down away from the ridge, this causes other plates to move away from each other
19
Q
What are convection currents
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
20
Q
What is the worldwide distribution of earthquakes and volcanoes
A
- Uneven distribution
- Mostly correlate with plate boundaries
- Earthquakes occur in linear chains (e.g. along west coast of South America) along all types of plate boundary
- Some earthquakes are away from plate boundaries (could be due to large plate movement or due to human activity such as building dams and reservoirs or fracking which puts a lot of pressure on the earth’s crust)
- Volcanoes also in linear distribution, around 3/4 in a ring around the Pacific, termed the ‘Pacific Ring of Fire’, and are related to destructive plate boundaries
- Some volcanoes aren’t on plate boundaries, these are hotspot volcanoes
21
Q
What are hotspot volcanoes
A
Isolated plumes of magma rise and move up through the crust to create a chain of volcanoes e.g. Hawaii
22
Q
What are the different types of plate boundaries
A
- Divergent (Constructive)
- Convergent (Destructive)
- Collision
- Transform (Conservative)
23
Q
What is a Divergent (Constructive) plate boundary
A
- Two oceanic plates move apart
- Creates effusive volcanoes and small earthquakes
- E.g. Mid Atlantic Ridge
24
Q
What is a Convergent (Destructive) plate boundary
A
- Oceanic plate subduct underneath a continental plate
- Creates powerful earthquakes and explosive volcanoes
- E.g. Nazca plate subducting under South American plate
25
What is a Collision plate boundary
- 2 Continental plates collide
- Caused powerful earthquakes and fold mountains
- E.g. Indian plate colliding with Eurasian plate
26
What is a Transform (Conservative) plate boundary
- 2 Continental plates slide past each other
- Creates powerful earthquakes
- E.g. Pacific plate and North American plate
27
What is the Constructive boundary volcano formation
Two plates move apart from each other (at a mid-ocean ridge, though can also happen at a rift valley with two continental plates moving apart). Magma rises to the surface at this weak spot and is extruded in eruptions, forming volcanoes when it solidifies to lava (remember magma in the mantle, lava on land)
28
What type of volcanoes do constructive boundaries form
Shield volcanoes
29
What are shield volcanoes
Short, gently sloping volcanoes composed of balsaltic lava due to its low viscosity (very runny) which have effusive (gentle compared to violent) eruptions which are free flowing and usually frequent e.g. Hawaii
30
What is the Destructive boundary volcano formation
Oceanic plate subducts underneath continental plate, the oceanic plate melts due to dehydration melting. Newly created magma rises to the surface and is erupted, forming a volcano over time as more material is erupted, cools, and solidifies to lava
31
What type of volcanoes do destructive boundaries form
Strato volcanoes
32
What are strato volcanoes
Tall, steep sided volcanoes composed of alternating layers of lava and pyroclastic flow / ash deposits due to sticky, high viscosity (thick) rhyolitic lava, traps gas causing build up of pressure and more explosive eruptions (+irregular)
33
Volcanic features
- Ash cloud
- Pyroclastic flow
- Crater
- Main vent
- Volcanic Bombs
- Secondary cone
- Lava flow
- Secondary vent
- Magma chamber
34
What do you use to measure eruptions
Volcanic explosivity index (VEI)
35
What are primary hazards of volcanic eruptions
Immediate effects resulting from the eruptions
- E.g. lava flow, ash, pyroclastic flow e.t.c
36
What are secondary hazards of volcanic eruptions
Things that happen as a result of primary hazards
- E.g. water contamination, infrastructure damage e.t.c
37
What is pyroclastic flow
A dense, fast-moving flow of solidified lava pieces, rock, volcanic ash, and hot gases
38
Mount Feugo Case Study Info
- LIC eruption
- 3rd June 2018, Mount Fuego, Guatemala
- 3763m high strato volcano in the Pacific ring of fire
- Cocos and Caribbean destructive plate boundary
- Country has high levels of poverty and political instability
- 48 km from Guatemala City
- Explosive Eruption (biggest for 500 years)
39
Mount Fuego case study primary hazards
- Ash cloud 10km high
- Pyroclastic flow over 100kmph
40
Mount Fuego case study secondary hazards
- Settlements such as El Rodeo devastated
- Airport closed
- 110 killed, 200 missing
- 12,000 evacuated, 3000 housed in temporary shelters
- 1.7 million effected
- 8500Ha of crop damage
- Traffic chaos from people trying to flee in their cars
- CONRED (national disaster management agency) accused of mismanaging disaster warnings
- Scientists warned of the eruption 8 hours before, but it took 3 hours for an evacuation order to be issued
41
What is an earthquake
A sudden and brief period of intense ground shaking
42
What is an earthquake caused by
1. Plates get stuck due to friction, often caused by protrusions (something that bulges out) on the opposite plate
2. Pressure builds up
3. Pressure gets too much and plates slip, the slipping motion causes energy to be released in the form of seismic waves, which is an earthquake
43
What plate boundaries do earthquakes occur at
All types
44
What is an earthquake epicentre
The epicentre is the point on the Earth's surface directly above the focus, where the seismic waves are most powerful
45
What is an earthquakes focus
The point inside the Earth's crust where the earthquake originates from
46
What are P waves
- Primary waves, pull ground side to side
- Can travel through solids and liquids
- Less dangerous than S wave (lower amplitude), but faster
47
What are S waves
- Secondary waves, pull ground up and down.
- Can only travel through solids
- More dangerous than P waves (greater amplitude), but are slower
48
What are precursor events before an earthquake
- Small tremors in preceding months
- Increase in radon emissions
- Indicators of previous earthquakes e.g. fault lines (fault scarps) and seismic gaps
49
What impacts amount of deaths in an earthquake
- Age of building / if they have been made ‘life safe’ or ‘earthquake proof’ via stringent building codes; remember ‘earthquakes do not kill people, buildings do’
- Infrastructure damage
- Potential for ground liquefaction
- Population density
- Poverty
- Poor governance
- Depth of focus (shallow focus (<10km) quakes will have a greater impact as closer to surface)
- Strength of earthquake
- Number of aftershocks
- Level of development
- Time of day
- Distance from epicentre
- Proximity to secondary hazards e.g. tsunamis, landslides e.t.c
50
What are earthquakes measured by
Measured on the Mercalli Scale (effects i.e. intensity) or Richter Scale (strength i.e. magnitude)
51
Turkey-Syria earthquake case study info
- 6th February 2023
- Magnitude of 7.8
- Deadliest and strongest recorded in Turkey since 1939 and deadliest in world since 2010 Haiti earthquake
- Epicentre was 34km west of city of Gaziantep (Southern Turkey and near northern border of Syria)
- On Anatolian plate, between the large tectonic plates of Eurasia, Arabia and Africa (2 major faults)
- Strike slip fault (plates stuck, pressure builds, then released), colliding with Eurasia plate and was squeezed to the west
- 10 hours after, 7.5 magnitude 128 km to north
- Shallow, 18km deep focus
- 4:17am, therefore people less alert and higher death toll
- Impact felt in Israel, Lebanon and Cyprus
52
Turkey-Syria earthquake case study primary hazards
- Significant shaking
53
Turkey-Syria earthquake case study secondary hazards
- Significant damage
- Over 56,000 killed, 100,000 people injured
- At least 4 million buildings damaged across Turkey
- Cracks on roads
- Hospitals in Turkey destroyed
- Runway of Hatay airport split and uplifted
- Gas pipeline exploded
- Gaziantep castle and several mosques severely damaged
54
What is the location of tropical cyclones
Tropical oceans 5-30° N/S of the equator
55
What are the different names for tropical cyclones
- Hurricanes in the Atlantic and eastern Pacific oceans
- Cyclones in the Indian Ocean
- Typhoons in the western Pacific
56
What is the formation and causes of a tropical cyclone
- Sea surface temperature of >27°C (allowing warm, moist air to rapidly rise; this forms an area of very low pressure)
- Converging winds (convergence of horizontal winds forces air to rise) near the oceans surface forcing air to rise and form storm clouds
- Clouds form in the tropics (due to warm air rising, cooling and condensing)
- These are low pressure systems (air is rising, therefore taking pressure off the earth)
- Winds that do not vary greatly with height- known as low wind shear, this allows the storm clouds to rise vertically to high levels
- Sufficient distance from the equator for spin from the Coriolis force to take effect
- Due to the Coriolis force, these clouds start to rotate (clockwise in the N hemisphere, anticlockwise in the S hemisphere)
57
How is the eye of a tropical cyclone formed
- Further aloft at about 6 miles, as winds spin inwards and upwards releasing heat and moisture, a cylinder of deep thunderclouds (cumulonimbus clouds) form
- The cloud tops are carried outwards by the outward-spiralling winds leaving the tropical cyclone core cloud free
- The cloud free centre of subsiding air, which is often dry with little wind, is referred to as the eye
58
How are tropical cyclones self-sufficient
- As the air descends, almost all, around 90% of the stored energy is released by condensation
- This release of heat energy warms the air and the pressure decreases further resulting in air rising faster to fill the area of low pressure
- As the air rises; warmer, moist air from the ocean is driven into the system, creating further energy and resulting in the tropical cyclone becoming a self-sufficient system
59
How do tropical cyclones break down
If the tropical cyclone travels over land, the energy source (tropical ocean) is lost which results in the eventual breakdown of the storm
60
What is the measurement for the classification of a tropical cyclone
- >34 mph wind speeds is a tropical storm
- Needs to be >74 mph to be called a hurricane/cyclone/typhoon
- Can be 300-500 miles across and 5-6 miles high
61
What are hurricanes measured by
Saffir-Simpson Hurricane Wind Scale from category 1 (74-95 mph, minimal damage, uprooting of some trees and a little flooding) to category 5 (>156 mph, catastrophic damage - buildings destroyed with small buildings being overturned. All trees and signs blown down. Evacuation of up to 10 miles inland)
62
Cyclone Idai case study info
- Mozambique, 14-15th March 2019
- LIC country, so has limited ability to respond to disasters
- UK aid raised was £18 million
- The UN Secretary General declared this “one of the worst-weather related catastrophes in the history of Africa”
63
Cyclone Idai case study primary hazards
- >150 mph winds
- 2.5 m high storm surge
- Flooding
64
Cyclone Idai case study secondary hazards
- Affected 2.6 million people
- Buildings, infrastructure and agricultural land destroyed
- >800 died
- Lack of access to food and basic services
- Many living in temporary camps without secure food supplies, portable drinking water and sanitation
- Increase in cases of diarrhoea, cholera and malaria in Beira, Mozambique, in particular
65
Vulnerability to hazards
Physical, social and economic factors that make some places more vulnerable, examples are:
- Poverty and development level
- Age of population
- Location of event
- Time of day
- Depth of focus
- Size of event
- How prepared the population were to respond
- Precursor events
- Amount of aftershocks
- Ability to predict
- Government stability
- If it’s a hazard hotspot
- Ability of population to adapt or mitigate
- Frequency of hazard event
- e.t.c.
66
What is the positives of living near volcanoes
- Jobs created e.g. tour guides, mining
- Fertile soil for farming (from volcanic ash acting like a fertiliser)
- Geothermal energy can be used to heat homes e.t.c
- Valuable minerals e.g. copper, gold, diamonds
- Tourist visit to see features like geysers, bringing money to the economy
- Can create new land
67
What are the negatives of living near volcanoes
- Risk of eruption
- Risk of contaminated water
- Mining can cause noise, air and dust pollution
- Ash can have negative impacts on infrastructure e.g. global supply chain disruption
- Destroy land during eruptions
- Poisonous gases and ash erupted that are harmful and can contaminate the air (especially bad for asthmatics)
68
Why do people live in areas at risk of earthquakes
- Ignorance of the risk - may not have been a large earthquake in living memory
- No social memory of an earthquake having occurred (i.e. in folklore)
- Wish to stay near relatives/where they grew up/good location e.t.c
- People do nothing and accept the hazard
- People adjust to living in a hazardous environment e.g. strengthening the home and preparedness
69
The hazard management cycle
HAZARD EVENT —> Recovery —> Appraise —> Risk assess —> Predict —> Prepare
70
How do you predict and prepare for a volcanic eruption
- It’s easier to predict and prepare for volcanic eruptions than it is for earthquakes
- Making hazard maps
- Using old deposits of lava, ash and pyroclastic flow material e.t.c to map a prediction of where these hazards would flow in a future eruption, this aids creating evacuation zone maps too
71
What does the prediction of earthquake use
Early warning systems (EWS)
72
What are earthquake precursor events that can lead to EWS
- Altered levels of radioactive radon gas
- Groundwater levels in wells changing
- Electrical signal changes
- Land tilting
- Erratic animal behaviour
- Precursor events - Mogi Doughnut Hypothesis (major earthquakes tend to occur in an unusually seismically calm area surrounded by a ring of unusually high seismic activity)
- Seismic gap theory (fault regions where no large earthquake has recently occurred, are more prone than others to host the next large earthquake)
73
What is vital for preparedness in buildings for earthquakes
- Building Design (earthquake proof or life safe buildings)
- E.g. those that have cross bracing and are built accordingly to more stringent design methods
- Remember saying ‘earthquakes do not kill people, buildings do’
74
What is vital for preparedness for an earthquake
- Building Design (earthquake proof or life safe buildings)
- Earthquake kits/drills
75
What are ways to prepare a building for an earthquake
- Shutters on windows prevent falling glass
- Small windows
- Reinforced walls
- Cross-bracing of steel frames
- Foundations sunk deep into the bedrock
- Frames which sway with the earthquake tremors
- Rubber shock absorbers to reduce tremors moving through the building
