challenge of natural hazards: tectonic hazards Flashcards
1
Q
natural hazard definition
A
a natural event that threatens people or has the potential to cause damage, destruction and death
2
Q
what is a natural disaster
A
a natural hazard that has actually happened
3
Q
what are the different types of natural hazards
A
atmospheric hazards
terrestrial/geological hazards
water based hazards
biological hazards
4
Q
what are atmospheric hazards
A
hazards created in the atmosphere, by the movement of air and water
5
Q
examples of atmospheric hazards
A
forest fires, hurricanes, tsunami
6
Q
what are terrestrial/geological hazards
A
hazards created by the movement of the Earth’s tectonic plates or surface rock and soils
7
Q
examples of terrestrial/geological hazards
A
cliffs, landslides, volcanic eruption, earthquakes, tsunami
8
Q
what is a water based hazard
A
hazards created by rivers, seas or oceans
9
Q
examples of water based hazards hazards
A
rivers, coastal floods, tsunami
10
Q
what is a biological hazard
A
any biological substance that poses a threat to the health of people
11
Q
examples of biological hazards
A
disease and drought
12
Q
what factors affect the impact of natural hazards
A
vulnerability
capacity to cope
nature of natural hazard
13
Q
what is hazard risk
A
the probability of people being affected by a hazard in a particular area
14
Q
how does vulnerability affect hazard risk
A
- the more people in an area exposed to natural hazards, the greater the probability they will be affected by a natural hazard
- for example, an area with high population density on a floodplain is very vulnerable to flooding caused by extreme weather, and a city at the bast of a volcano is very vulnerable to volcanic eruptions
15
Q
how does capacity to cope affect hazard risk
A
- the better a population can cope with an extreme event, the lower the risk of them being severely affected
- for example, HICs are better able to cope with flooding because they can build flood defences and evacuate people
- for example, place that have more natural hazards would have more experience in preventing them and keeping people safe
16
Q
how does the nature of natural hazards affect the hazard risk
A
- type - the risk from some hazards is greater than other
(eg. topical storms can be very predicted and monitored, giving people time to escape but earthquakes can happen very suddenly, with no warning, so its much harder to protect people) - frequency - natural hazards that occur more often may carry a higher risk
- magnitude - more severe natural hazards tend to have greater effects
17
Q
what are primary effects
A
immediate impacts caused by the hazard itself
18
Q
examples of primary effects
A
- buildings and roads destroyed by earthquakes, volcanic eruptions or tropical storms
- people are injured or killed (eg. when buildings collapse)
- crops and water supplies can be damaged or contaminated
- electricity cables gas pipes and communication networks can be damaged, cutting off supplies
19
Q
what are secondary effects of natural hazards
A
they happen later on, often as a result of primary effects
20
Q
examples of secondary effects
A
- the initial hazard can trigger other hazards (eg. earthquakes can trigger tsunamis)
- aid and emergency vehicles can’t get through because of blocked roads or bridges - this can cause more deaths
- a shortage of clean water and a lack of proper sanitation makes it easier for disease to spread
- food shortages can occur if crops are damaged, livestock are killed or supply lines are blocked
- the country’s economy can be weakened - damage to businesses can cause unemployment, and the reconstruction process can be very expensive
21
Q
examples of immediate responses to natural hazards
A
- evacuate people (before hazard occurs if possible)
- treat the injured and rescue anyone cut off by the damage to roads and bridges
- recover the dead bodies to prevent disease spreading
- provide temporary supplies of electricity and gas if regular supplies have been damaged
- provide food, drink and shelter to people without homes
- foreign governments or charities may send in aid workers, supplies or financial donations
22
Q
examples of long term responses to natural hazards
A
- repair homes or rehouse people who have lost their homes
- repair or rebuild buildings, roads, railways and bridges
- reconnect broken electricity, water, gas and communication connections
- improve forecasting, monitoring and evacuation plans
- improve building regulations so that buildings can withstand similar hazards in the future
- boost economic recovery (eg. by promoting tourism)
23
Q
what is the case study for tectonic hazards
A
Eyjafjallajökull eruption, Iceland
24
Q
what tectonic plates are Iceland on
A
North American plate and Eurasian plate
25
when did Eyjafjallajökull erupt
14th April 2010
26
what type of plate boundary is eyjafjallajökull located on and what’s it called
a constructive plate boundary
known as the mid-atlantic ridge
27
what crusts are tectonic plates made of and what are they like
- CONTINENTAL crust is thicker (30-50km) and less dense
- OCEANIC crust is thinner (5-10km) and more dense
28
how do tectonic plates move
- convection currents
- slab pull
- ridge push
29
convection currents (in movements of tectonic plates)
- hot core causes magma to rise in the mantle and sink towards the core when it cools
- convection builds pressure and carries plates with it
30
slab pull (in movement of tectonic plates)
- the denser plate sinks back into mantle under the influence of gravity
- it pulls the rest of the plate along behind it
31
ridge push (in movement of tectonic plates)
- magma rises as the plates move apart
- the magma cools to form new plate material
- as it cools, it becomes denser and slides down away from the ridge
- this causes tectonic plates to move away from each other
32
what is continental drift
- the tectonic plates moving over millions of years, breaking away bits of land
- the plates either rub against each other in opposite directions or the same direction but different speeds
33
destructive plate margin:
- this is where two plates are moving TOWARDS each other
- when an oceanic plate meets a continental plate, the denser oceanic plate is subducted (forced down into the mantle) and destroyed, creating gas-rich magma
-> volcanoes and ocean trenches occur here
- where two continental plates meet, the ground is folded upwards, creating fold mountains
- eg. along the west coast of South America, the oceanic Nazca plate is being subducted beneath the continental South American plate, creating the Atacama Trench
34
constructive plate margin:
- where two plates are moving AWAY from each other
- magma rises from the mantle to fill the gap and cools, creating a new crust
- eg. the movement of the Eurasian plate and the North American plate away from each other is forming the mid-Atlantic ridge
35
conservative plate margin:
- where two plates are moving SIDEWAYS past each other or are moving in the SAME DIRECTION but at DIFFERENT speeds
- crust isn’t created or destroyed
- eg. at the San Andreas Fault, the Pacific plate is moving in the same direction as the North American plate, but faster
36
summary of what happens at destructive plate margin:
1) destructive plate boundary is found where a continental plate meets an oceanic plate
2) plates are moving towards each other because of the convection currents
3) the oceanic plate subducts (descends) under the continental plate because it is denser
4) where the two plates intersect a deep trench forms
5) earthquakes occur at various depths along the subduction zone where the plate sticks and pressure builds up
6) when the plate has descended below 100km it starts to melt due to the rising temperature and pressure as it moves into the mantle
7) this hot, liquid rock (magma) is now less dense than the surrounding rock and rises through the gaps in the continental plate
8) most of the molten rock cools and solidifies in huge sponge-like magma chambers far below the earths surface
9) if it reaches the surface, there is an explosive eruption of gases, ash and lava
37
summary of what happens at constructive plate margins:
1) a constructive plate boundary is found where two plates move apart and new crust is formed at the boundary
2) an example is found the the Atlantic where there is sea floor is spreading where the North American and Eurasian plates are being pulled apart by convection currents
3) initially rift valleys form on the sea floor
4) magma rises from the mantle to fill the gap between the plates forming sub marine volcanoes which in time may grow above sea level
5) as the basaltic magma cools, it adds new land to the separating plates. the Atlantic Ocean is widening by 2 - 5cm per year
38
summary of what happens at conservative plate margins:
1) conservative plate margins occur where two plates move parallel or nearly parallel to each other. crustal rocks are neither created or destroyed here
2) the boundary between the two plates is characterised by pronounced transform faults
3) as the plates move past each other, they can stick until pressure builds up. suddenly there is a release of pressure and the plate jerks forwards and energy is released in the form of seismic waves, causing an earthquake
39
summary of what happens at collision plate margins:
1) a collision plate margin happens when two continental plates are moving towards each other and collide
2) neither plate can be destroyed so they are formed upwards and downwards
3) the upwards section make fold mountains (the Himalayas were made like this) and the downwards section makes mountain roots
4) you get high magnitude earthquakes at collision boundaries because there is a massive buildup of friction and pressure
5) however, because no plate is being destroyed, magma is not being created, so you do not get volcanoes
40
what plate margins do volcanoes form at
destructive and constructive
41
how do volcanoes form
1) at destructive margins, the denser oceanic plate moves down into the mantle, where it melts. a pool of magma forms, which then rises through cracks in the crust called vents. this magma (called lava when it reaches the surface) erupts, forming a volcano
2) at constructive plate margins, the magma rises up into the gap created by the plates moving apart forming a volcano
3) some volcanoes also form over parts of the mantle that are really hot (called hotspots), eg. Hawaii
4) when a volcano erupts, it emits lava and gases. some volcanoes emit lots of ash, which can cover land, block out the sun and form pyroclastic flows (super-heated currents of gas, ash and rocks)
42
what are earthquakes caused by
a buildup of tension at plate margins
43
how does tension occur at destructive plate margins
tension builds when one plate gets stuck as it moves past the other plate
44
how does tension occur at constructive plate margins
tension builds along cracks in the plates as they move away from each other
45
how does tension occur at conservative plate margins
tension builds up when plates that are grinding past each other get stuck
46
how do earthquakes happen
1) earthquakes are caused by a buildup of tension at plate margins
2) the plates eventually jerk past each other, sending out shock waves - these vibrations are the earthquake
3) the shock waves spread out from the focus (the point in the earth where the earthquake starts). the waves are stronger near the focus and cause more damage
47
what is the focus
the point in the earth where the earthquake starts
48
where are the waves of an earthquake strongest
nearer the focus
49
what is the epicentre
the point on the earths surface straight above the focus
50
how are earthquakes measured
- the MERCALLI scale
- the RICHTER scale
51
what does the moments magnitude scale measure about earthquakes
the amount of energy released (the magnitude)
52
earthquakes of magnitude 6 and below:
normally only cause slight damage to buildings, although they can be worse in very built up areas
53
earthquakes of magnitude 7 and above:
can causes major damage and death
54
how do volcanic eruptions happen
1) molten heat originates in the mantle, which in turn is powered by the earths inner heat
2) driven by buoyancy and gas pressure molten rock, which is lighter than the surrounding solid rock, forces its way upward into magma chambers within the earths surface rocks
3) this material accumulates and can exert pressure on the surface, forcing it to bulge upwards
4) some of this material is then forced under pressure to rise towards the earths surface through fissures and cracks, where it will be blocked by solid rock
5) ultimately, the pressure becomes so great that this magma breaks through zones of weakness in the earths crust. this is where the eruption begins
6) composite cone volcanoes with steep sides and layers of dust, ash and tephra have a high gas pressure and release sticky lava OR shield volcanoes with a flatter profile and layers of solidified magma have a low gas pressure and release runny lava
55
primary effects definition
immediate impacts of the eruption or earthquake
56
secondary effects definition
happen later on, or as a result of primary effects
57
what was the magnitude of eyjafjallajökull eruption
category 4 VEI (volcanic explosively index)
58
how many flights were cancelled due to the eyjafjallajökull eruption
95,000
59
primary effects/impacts of the eyjafjallajökull eruption
- ash cloud coated europe
- eruption melted part of the ice cap on the volcano causing flash flooding in the surrounding area
-
60
what was the secondary effect of the ash cloud from the eyjafjallajökull eruption
- 95,000 flights cancelled
- hotel occupancy was down by 25%
- people were stuck in different countries
- flights in european airspace fell from 25,000 a day to only 5000
- cost to the airline industry was approximately $2 billion
61
immediate responses of the eyjafjallajökull eruption
- evacuate nearby farmers and Icelandic people
-> 20 farming families had been evacuated from the area threatened with flash floods
- get animals to safety with plenty of food
- trenches were dug to allow floodwaters to pass without washing away bridges
62
long term impacts/responses to the eyjafjallajökull eruption
- iceland became more popular
- animals had damaged lungs
- fertile land
63
effect of the eyjafjallajökull eruption on london
- on a normal day in april about 30,000 oversea visitors arrive by air
- they spend a total of £17 million a day
- the 6 day flight shutdown cost london about £102 million
- hotel occupancy was down 25%
- shops, restaurants and theatres all had a fall in customers
- estimated 100,000 people who should have flown home were stranded in london
-> they didn’t spend any more money than was necessary
64
what does the mercalli scale measure
the amount of damage caused by an earthquake -> gives an indication of the intensity of the earthquake + refers to the effects on humans/buildings/landscapes
65
what does the richter scale measure
the magnitude of an earthquake -> it is based upon measurements of earthquake waves from instruments
66
what is the HIC earthquake case study
L’Aquila, Italy
67
what is the LIC earthquake case study
Gorkha, Nepal
68
in L’Aquila how big was it on the richter scale
6.3 on the richter scale
69
how far away was the earthquakes epicentre from L’Aquila
7km north-west of L’Aquila
70
when was the L’Aquila earthquake
6th April 2009
71
what was the GDP per capita of L’Aquila
US $11,434 million
72
primary effects of L’Aquila earthquake
- 308 dead, 1500 injured, 67500 homeless
- many churches + medieval buildings collapsed
- the Basilica was severely damaged
73
secondary effects of L’Aquila earthquake
- aftershock triggered landslides + rockfalls
- the number of students at L’Aquila uni has decreased
- house prices + rent increased
- burst main water supply
74
immediate responses to L’Aquila earthquake
- hotels provided shelter for 10,000 people made homeless
- 40,000 tents were given out
- the italian post office offered free calls
- declared a state of emergency
75
long-term responses to L’Aquila earthquake
- residents didn’t have to pay tax in 2010
- students were given free public transport, discounts from educational equipment and were exempt from uni fees for 3 years
76
how big was the Gorkha earthquake on the richter scale
7.8 magnitude earthquake
77
where was the epicentre of the Gorkha earthquake and how far away was it from the capital
epicentre was in Barpak and was 80km away from the capital, Kathmandu
78
when was the Gorkha earthquake
28th April 2015
79
GDP per capita of Gorkha
US $6.7 billion
80
primary effects of gorkha earthquake
- 8841 dead, over 16,800 injured, 1 million made homeless
- people were trapped in buildings
- 26 hospitals + 50% of schools were destroyed
81
secondary effects of gorkha earthquake
- avalanche on Mt. Everest
- food shortages + income loss - happened just before monsoon season so rice couldn’t be planted and grown
82
immediate responses to gorkha earthquake
- nepal requested international help
- temporary shelters were set up
- the Red Cross provided tents for 225,000 people
- 315,000 people were cut off by road - facebook launched a safety feature so people could indicate they were ‘safe’
83
long-term responses to gorkha earthquake
- post disaster needs assessment was carried out
- 23 areas required re-building
- mt.everest was re-opened to tourists by august 2015
- US $274 million had been committed to recovery efforts
84
why do people in live in areas at risk from tectonic hazards (not by choice)
can’t afford to move or may not know the risks
85
why do people CHOOSE to live in areas at risk from tectonic hazards
- they’ve always lived there - moving means leaving their jobs or families
- in wealthier countries, effective monitoring and evacuation plans can minimise risk
- they’re confident that their gov will support them after earthquake or volcanic eruption (eg. in 2001, the italian gov provided financial aid and tax breaks for local residents when mount etna erupted
- the minerals from volcanic ash makes volcanic soil very fertile, attracting farmers (eg. the mineral-rich soil around mount etna is ideal for producing grapes)
- volcanoes are tourist attractions, so lots of people live nearby to work in the tourist industry - mount etna receives hundreds of thousands of visitors when it is erupting
86
what type of management strategies can be used to reduce the effects of tectonic hazards
- monitoring
- prediction
- protection
- planning
87
how can monitoring be used to reduce the effects of natural hazards
earthquakes - seismometers and lasers monitor earth movements, and can be used in early warning systems to give a small but vital amount of warning before a large earthquake occurs
volcanic eruptions - scientists can monitor the tell-tale signs that come before an eruption, such as tiny earthquakes, escaping gas and changes in the shape of a volcano
- changes in shape of the ground and volcano using tiltmeterers and GPS satellites
- radon and sulphur gas using gas-trapping bottles
- ground surface + river temps using thermal heat sensors
88
how can prediction be used to reduce the effects of natural hazards
earthquakes - cannot be reliably predicted, but scientists can forecast where they may occur by monitoring the movement of tectonic plates
volcanic eruptions - can be predicted if scientists monitor volcanoes closely
89
how can protection be used to reduce the effects of natural hazards
earthquakes - new buildings can use reinforced concrete that absorb an earthquakes energy. existing buildings and bridges can be strengthened with steel frames so they’re less likely to collapse. automatic shut-off switches can turn off gas and electricity supplies to prevent fires
volcanic eruptions - buildings can be strengthened so that they’re less likely to collapse under the weight of ash. trenches and barriers have been used to try to divert lava away from settlements, but with little success
- sea walls in case of tsunamis (from earthquakes)
- evacuation instructed by authorities (eruption)
90
how can planning be used to reduce the effects of natural hazards
- future developments can avoid high-risk areas
- emergency services can prepare, eg. by practicing rescuing people from collapsed buildings
- people can be educated so that they know what to do in the event of a hazard
- governments can plan evacuation routes to get people away quickly and safely
- emergency supplies like blankets, clean water and food can be stockpiled
