Tectonics Flashcards
1
Q
What is the key characteristic of lavas?
A
- Silica content
2
Q
What are seismic waves?
A
- Waves of energy which travel through the crust caused by the release of pressure from an EQ or volcano.
3
Q
How might the population size and density impact on EQ severity?
A
- Larger and denser the pop. in an EQ zone, the more people at risk
- Izmit, Turkey, 1999- Rapid population increases, migrants crammed into high density housing
4
Q
Describe the characteristics of Plinian Eruptions?
A
- Magma has high silica content
- Highly explosive
- AD79 Pompeii and Herculaneum eruption.
- Started by highly viscous magma with high gas content.
- Can last several days
- Tall eruption plume with destructive lava flows.
5
Q
What are the factors which might impact on earthquake severity?
A
1) Time of day
2) Population size and density
3) Housing quality
4) Economic development
5) Geology
6
Q
What biological evidence did Wegener find?
A
- Fossil evidence which is essential
- Specific fern found in Africa, Antartica, Australia and S. America. This provided evidence that the continents must have been joined some 250 million years ago.
- The Mesosaurus is an extinct reptile that has been found in Africa and South America. As it was a coastal animal it couldn’t have crossed the Atlantic ocean.
7
Q
What caused the Northridge, california, 1994 EQ?
A
- January 1994, 4:31am- 6.7 magnitude
- San Andreas Fault
- Densely populated
8
Q
Describe tsunami formation?
A
1) As the sea floor lifts, billions of tonnes of water are displaced.
2) Seconds later, the tsunami undergoes a rapid transformation as the displaced water column collapses and splits.
3) Water rushes away from the uplifted area creating a tsunami wave that travels radially outwards from the centre.
4) In deep water, tsunamis can reach 1000km/h. The wave height is only 1m and the wavelength is about 200km. The circular motion make it very powerful.
5) As it approaches the coast, the gradient of the beaches causes the bottom of the wave to slow due to friction. Consequently, wavelength decreases and height increases. The crest of the wave carries more energy so are exaggerated destructive waves.
9
Q
What do characteristics of tsunamis depend on?
A
- Height of waves and distance travelled.
- length of event e.g. EQ
- Coastal physical geography
10
Q
What happens at the destructive continental- continental plate boundary?
A
- Unlike the first two destructive margins, when two continental plates are drawn together neither will be subducted.
- Volcanicity and sediments are mixed and compressed to form fold mountain chains with deep roots in the Lithosphere.
- India was propelled by sea floor spreading by the indo-Australian plate before colliding with the Eurasian plate resulting in the Himalayan mountain chain.
- Such areas remain seismically active and so the Himalayas are constantly changing.
- However, this activity also causes devastating EQs such as Pakistan, 2005.
11
Q
How might low frequency electromagnetic activity warn of an EQ?
A
- Sometimes referred to as VAN method. Based on the assumption that minerals under mechanical stress emit characteristic electrical signals.
- Electric signals move along the fault line and the signals are detected in stations underground.
- method has been shown to monitor small EQs- 2.5m but is limited in recording higher magnitude ones.
12
Q
What happens at the destructive oceanic-continental plate boundary?
A
1) Oceanic crust is denser than continental crust, so when they collide the oceanic is subducted into the Asthenosphere.
2) Friction between the two plates builds and causes major earthquakes in the Benioff Zone.
3) Rocks scraped from the Oceanic crust and folding of continental crust creates fold mountain chains.
4) Ocean tenches found along the seaward edge of margins- mark subduction zone
5) Friction also generates heat leading to partial crust melting and the release of gases like CO2.
6) Magmas derived from melting of old crust basalts rises through fissures because they are less dense. They are more viscous because they are more silica rich. These lavas often block off their own vents resulting in violent explosions and the formation of conical shaped volcanoes- fold mountains.
13
Q
What are the advantages of planning?
A
- Highly effective in searching for better research techniques
- Very successful- allows better buildings in the future.
14
Q
What were the causes of the Haiti EQ?
A
- North American plate sliding past the Caribbean at a Conservative plate margin
- Most densely populated area of the country
- Being in a poorly constructed, large urban area reduced chances of survival
- EQ of same magnitude occurred in China one month earlier but has far less impact.
15
Q
Why are poisonous gases and acid rain dangerous?
A
- CO2, carbon monoxide, hydrogen sulphide, sulphur dioxide and chlorine.
e. g. CO2 emissions from Lake Nyes in Cameroon caused 1700 suffocations.
16
Q
What are the hazards associated with volcanic eruptions?
A
- Lava flow
- Pyroclastic flow
- Volcanic bombs
- Lahar
- Poisonous gas, causing acid rain
17
Q
Describe the preparation for the Mt. Pinatubo eruption?
A
- Non considered hazardous
- Signs of eruption earlier in the month
- Advanced warning allowed evacuation of 1000s of people.
18
Q
What is a tertiary impact?
A
- Long term effects as a result of a primary effect which will last years into the future.
19
Q
What are the characteristics of intra plate EQs?
A
- Rare- account for less than 10% of EQs
- Low magnitude
- Longer recurrence intervals
- Seismic waves move more slowly.
20
Q
Give an example of a caldera?
A
- Santorini, Greece
21
Q
Describe the hawaiian hotspots?
A
- The Hawaiian islands provide striking evidence of the tectonic phenomenon.
- Stretching north west of the main island is a string of smaller islands and submerged volcanoes of sea mounts, 3700 miles long.
- Each one of these islands was formed where the main island now stands.
22
Q
Give a timeline of events for the San Andreas fault?
A
1906- Great San Fransisco Quake- Fires raged for 4 days, 1/10 buildings destroyed, 3,000 dead, 7.8 magnitude, Andrew Lawson and team discover the fault.
1994- 6.7 magnitude- 72 dead, 12,000 injured
Late 20th century- Theory of plate tectonics revealed the Pacific plate had been subducted under the N.American plate for 100 million years.
2004- Later than expected EQ in Parkfield.
Recent studies- Suggest stress and another possible EQ
2008- Quake drill
100 years- 99% chance of major quake. New type of superwave discovered- predicted quake could result in 2000 deaths, 50,000 injuries and $200 billion worth of damage.
20 million years- San Fransisco and LA will be aligned.
23
Q
What are the three categories of volcanic activity?
A
- Extinct, active, dormant
24
Q
What were the secondary impacts of the California 1994 EQ?
A
- Decrease in tourism
- Damage to major freeways- congestion
- Los Angeles International and Burbank airports closed.
25
What is a volcanic cone?
- Simple volcano built up over a series of eruptions
| - e.g. Mt. Etna, Italy
26
What is a ocean ridge?
- Ocean form the longest continuous uplifted feature on the Earth's surface with a combined length of 60,000Km
- The Mid- Atlantic Ridge is 10,000 miles long and occupies the centre of the Atlantic Ocean. Its sea floor can spread up to 4 inches every year.
27
Give some examples of extrusive landforms?
- Lava Plateaux
- Basic/shield volcanoes
- Acid/dome volcanoes
- Composite cones
- Ash and cinder cones
- Calderas
28
Give information about the 2008 EQ in Market Rasen, Lincolnshire
- 5.2 magntiude
- Rupture at a strike slip fault
- Distant tectonic stresses- British isles squeezed by plates
- People contacted the police
- Minor building damage
- Broken pelvis
- St Magdalene's church spire was damaged and rebuilt at a cost of £100,000
29
How might economic development impact upon EQ severity?
- poorer countries often don't have the resources to put in place effective emergency procedures to deal with the immediate impact of EQs.
- Haiti, 2010- magnitude of 7, make shift camps, poor sanitation led to worst cholera outbreak in history, in 2015 6% of pop. were ill with cholera.
30
What do geller, jackson and Kagan say about predicting EQs?
- It is not possible.
- Prediction would have to be reliable and accurate to justify the cost.
- Inaccessibility of the fault line
- prediction is not feasible
- Reasons to doubt that such precursors exist.
31
How do ocean ridges, submarine volcanoes and islands form?
1) First step in constructive plate margin
2) Where the two weaker plates have pulled apart there is a weaker zone where the temperature is higher. This hotter, expanded crust forms a ridge.
3) In the central part of the ridge, there may be a central valley where a section of the crust has subsided into the magma below.
4) The split in the crust provides a low pressure zone where more magma can erupt to form submarine volcanoes
5) If such eruptions persist, volcanoes may develop to reach the surface forming volcanic islands e.g. Iceland.
6) As crust is pushed away from the heat source, it cools and sinks, becoming covered in fine sediment. Consequently, new ocean lithosphere is formed and the ocean basin gets wider- sea floor spreading.
32
Describe primary waves?
- Body waves
- Compressional/longitudal
- Particles vibrate parallel to the direction of movement
- Passes through solids, liquids and gases.
- Refracted by the changing densities of the mantle.
- Forms shadow zone.
33
What are the characteristics of acid lava?
- High silica content
- High temperature
- Very viscous
- Potentially explosive; lava shatters into pieces
- From time to time; long dormant periods
- Acid lava dome composite cone, layers of ash and lava, column of gas and finer fragments.
34
How doe rift valleys occur?
1) Constructive plate margin- convection currents in the Asthenosphere cause continental crust to dome upwards.
2) Upwards pressure causes the crust to crack, leaving an unsupported middle section.
3) This unsupported section collapses, forming a rift valley with steep sides.
4) If the convection currents are strong enough, a line of volcanoes will form at the bottom of the rift valley, producing basaltic rock which will eventually form an ocean floor.
35
Who is supportive of fracking?
- Many governments
| - Big companies like Shale Gas Europe
36
What can inactive volcanoes be called?
- Inactive volcanoes which have not erupted for an amount of time but can't be called extinct are dormant.
- Inactive volcanoes which have not erupted since the beginning of recorded history are extinct.
- They will only erupt again if they are actually dormant.
37
How do spring bases help prepare for the possibility of an EQ?
- Spring with damper base is designed to absorb the seismic shocks during the EQ and add stability to the structure.
38
What are the disadvantages of prediction?
- None of the predictive methods achieve the SSA's criteria for a valid prediction.
- Reliability has been questioned
- Methods only successful in a narrow band of EQs
39
What are the 4 options for managing the threat of volcanic eruptions?
1) Monitoring and prediction
2) Evacuation
3) lava diversion
4) Lahars
40
What landforms are associated with destructive plate margins?
- Fold mountains
- Ocean trenches
- Conical shaped volcanoes
- Island arcs
- landmasses
41
What is EQ prediction like?
- there is no reliable way to predict the day or month when an event will occur in a specific location. An EQ prediction is a prediction of what magnitude will occur and where and when it will be.
42
Describe what a acid/dome volcano is?
- Steep-sided convex cone consisting of viscous lava
43
What were the short term responses to the Mt. Pinatubo eruption?
- Within 3 weeks some people began to return
| - Some of the Aeta tribe didn't return
44
Describe long waves?
- Long frequency period
- Referred to as surface waves
- Rayleigh waves and Love waves
- Rayleigh waves have a vertical circular movement
- Love waves have a horizontal circular movement.
45
What are the long term economic impacts of EQs?
- Cost of rebuilding is high- may impair development
- Investment may only focus on repairs
- Income lost
46
What are convection currents?
- Hot spots around the core of the earth which generate thermal convection currents where hot magma rises before spreading cooling and sinking.
- The process us continuous and is the driving force behind the movement of the tectonic plates.
47
Give the fact file for the 2011 Japanese Tsunami?
- Northeast Honshu
- 4:46pm, March 2011, triggered by a magnitude 9 EQ.
- Pacific- N. America subduction zone
48
What were the secondary impacts of the Northeast Honshu tsunami?
- Entire communities have been wiped out
- Nikkei Index dropped 1.7% (financial market)
- Industry halted- Honda, Toyota, Sony
- Crops and fishing damaged
- Fukushima- 30 mile exclusion zone
49
What are some tertiary impacts of a hazard event?
- People might have a lower quality of life and the country might struggle to develop.
50
What climatological evidence did Wegener find?
- Coal formed under warm , wet conditions found under the ice cap, therefore must have been nearer equator, hence has moved with time.
- Evidence of glaciation noted in Brazil and Central India (coal, sandstone and limestone could not have formed in present climate).
51
What is fracking?
- A way of mining for hard to reach gas reserves/oil
- Shale-sedimentary rock
- High pressure water systems
- Contains additional chemicals
52
What is a tsunami?
- A rapid change to the volume of the ocean
53
Give an example of a basic/shield volcano
- Mauna Loa, Hawaii
54
How do people perceive the risk of a natural hazard?
- Whether the area is profitable to live in- Mt. Vesuvius has 3x average crop yield.
- Day to day problems more important
- Have the capital and technology to cope with the event e.g. Japan
- Past experiences of a hazard
- Attitudes towards risk- 'Act of God', optimist vs pessimist
55
What geological evidence did Wegener find?
- Rocks of similar age, type and structure occur in SE Brazil and Africa
- Appalachian mountains of Eastern USA correspond geologically with mountains in NW Europe.
56
How has Istanbul's airport been prepared for EQs?
- World's largest EQ proof building
- Built to withstand magnitude 8 EQ and remain fully functional
- 300 separate devices isolate the entire building from the ground.
- Confluence of three tectonic plates with high recurrence intervals so need to maintain operations.
57
Give the background to the Mt. St Helens eruption?
MDC- Washington
Morning in May, 1980
Destructive plate margin
Oceanic Pacific and Continental N.American
Main vent became blocked, causing a bulge
58
What are the three types of destructive plate boundraries?
- oceanic-continental
- oceanic- oceanic
- Continental-continental
59
Can humans cause EQs?
- 25% of Britains recorded seismic events have been caused by people
Human activity which might cause an EQ:
1)Fluids pumped out of the ground e.g. oil
2) Creation of new water reservoirs e.g. Hoover dam- up to magnitude 5 in the decade following construction.
3) Disposal of toxic waste.
4) Underground mines e.g. Uzbekistan- up to 7.3
60
What were the secondary effects of the Mt.St Helens eruption?
- 1 million trees flattened
- People burnt up to 16 miles away
- Loss of farm land
- 300km road and 250km railway destroyed
- Melting glaciers formed lahars
- 57 dead
61
What are the different kinds of seismic waves?
1) Primary waves
2) Secondary waves
3) Long waves
62
What are the long term social impacts of EQs?
- Disease
| - Re-housing and refugee camps
63
What is geomorphology?
The study of the landforms of the earth's surface
64
Give the fact file for the BAM EQ in Iran?
- 5:26am on the 26th December 2003
- Magnitude 6.5
- 30,000 dead in 24hrs
- 20,000 injured
- $1 billion rebuilding costs
65
What is a hazard event?
A natural hazard is only a hazard event if it poses a threat to people or property + disruption e.g. Mt. St Helens- 57 dead
66
What evidence is there that fracking many lead to seismicity?
- Strange places
- 50 EQs in Oklahoma linked to fracking.
- Result from fractured rock
- Millions of gallons of water disrupts natural equilibrium
67
What are the causes of tsunamis?
- Shallow focus EQs
- Volcanic eruptions
- Underwater debris slides
- Large landslides into the sea
68
What are the short term environmental impacts of an EQ?
- Fires
- Landslides
- Tsunamis
- landscape destroyed or damaged
69
Describe the characteristics of Hawaiian eruptions?
- Basic and basaltic lava with low gas pressures and silica content.
- Not explosive or destructive with no tephra or pyroclastic flow.
- Produces gentle sloped shield volcanoes and lava plateaus
- Lava fountains up to 50m in the air.
70
What were the primary impacts of the Northeast Honshu tsunami?
- Waves up to 6m high
- Flooding up to 15km inland
- Debris
- $100 trillion
- Shortages of food, water and shelter
- 30,000 dead
- 500,000 homeless
71
How might the time of day impact upon EQ severity?
- An EQ that strikes at night when most people are asleep will cause more deaths and injuries
- Izmit, Turkey, 1999- EQ occurred in August at 3:02am, resulting in 17,000 dead and 27,000 injured- 1/10 of pop.
72
Give the background to the Mt. Pinatubo eruption?
- LDC- Angeles, Phillipines
- June 1991
- Destructive plate boundary
- Oceanic Philippines and Oceanic Eurasian
73
What are the options for predicting EQs?
1) Seismic activity
2) Radon
3) Groundwater
4) remote sensing
5) Low frequency electromagnetic activity
74
What were the primary effects of the Mt. St Helens eruption?
- landslide of 8 billion tonnes of material at 250mph.
- Ash column 15 miles into the air
- Pyroclastic flow at 650mph
75
What were the long term responses to the Mt. Pinatubo erutpion?
- Majority of residents never returned
76
Why are there different theories about hot spots?
- Of 125 active hotspots, most are located away from plate boundaries. This poses issues for the plate tectonic theory as they show that not all seismic and volcanic activity happens at plate margins.
77
What is an example of a rift valley?
- The Great east African Rift Valley has active volcanoes such as Mt. Kilimankaro and Kenya and has resulted in the creation of the Red Sea. It is 4000km long, 50km wide and 600m in depth.
78
What is a secondary impact?
- A consequence of the primary impact
79
What is a natural hazard?
An extreme event in the natural environment which has the potential to cause harm to either people or property
e.g. Ireland of Surstey forming submarine volcanic eruption which created a new island.
80
What were the primary impacts of the 1994 California EQ?
- Thousands of aftershocks
- 57 killed and 1500 injured.
- 3 days later 9000 homes and businesses without electricity, 20,000 without gas and nearly 50,000 without water
- 6% buildings severely damaged, 17% moderately damaged
- landslides and fires
81
Describe the timeline of events for the boxing day Tsunami?
1) Hits Banda Aceh
2) Hits Thailand 20 minutes later
3) 2 hours after it reaches Sri Lanka
4) After 7 hrs it had travelled 3000 miles to Africa.
82
Describe the locations of tsunamis?
- generated at destructive plate margins.
- 90% events in the pacific ocean
- 25% events off the Japan- Taiwan island
- 4% occur in Indian Ocean
83
Who created the theory of continental drift?
- Alfred Wegener
84
What factors made Northeast Honshu vulnerable to the 2011 tsunami?
- Four major tectonic plates meet in the Japan region.
- coastal areas low lying and densely populated.
- extensive preparations with 40% of coastline protected. $1.5 billion spent on new sea wall.
- Early warning systems were ineffective because the EQ occurred so close to the coast.
85
What are the characteristics of tsunamis?
- Become steeper in shallower water
- Drawback
- Large waves radiate from the epicentre
- can travel long distances
- Ricochet off land masses
- Waves rarely felt in deep water
- Consists of numerous waves, largest till last.
86
What factors make an area vulnerable to hazards?
- Population density
- Existence of an early warning system
- Constructions styles and building codes
87
What were the causes of the 2011 New Zealand EQ?
- February 2011, 12:51pm- 6.3 magnitude
- EQ only 5km deep
- Conservative plate margin where the Pacific and Australian plates move past each other
88
What are EQs?
- Vibrations in the earths crust that cause shaking at the surface. 50,000 occur every year, mainly on plate margins.
89
What were the long term responses to the Haiti EQ?
- The Haitian government made a statement that confidence needed to be regained in the way the country is governed and wanted to encourage the democratic process and modernise the justice system.
- preliminary damage and Needs Assessment (PDNA) recommended money should be spent on improving disaster prevention.
- Reconstruction money will be spent on providing free primary education for all, improving access to health services and reducing malnutrition.
- Mass- relocation schemes considered.
90
Describe a caldera?
- Occur when the build-up of gases become extreme and a huge explosion removes the summit of the cone, leaving an opening several Km in diameter.
- The Caldera may become flooded by the sea, or a lake may form within it.
91
What are the characteristics of EQs?
1) Seismic waves
2) Epicentre
3) Focus
92
What are the intrusive features?
- Batholith
- Sills
- Laccolith
- Dyke
93
What is a rift valley?
- Valleys in the Earth's surface which have developed due to sea floor spreading and convection currents in the mantle.
- When seafloor spreading occurs under a landmass, the heating and subsequent doming of the crust leads to fracturing and rifting.
- As the sides of the rift move apart, central sections drop down.
94
How are hotspots formed?
1) Small long-lasting and hot regions below the plates provide localised thermal plumes.
2) Island chains may result from the plate moving over a deep, stationary hotspot in the mantle.
3) Hotspots provide a continuous source of magma which is lighter than the surrounding solid rock and consequently rises to the seafloor forming active seamounts.
4) Over time, countless eruptions cause the sea mount to grow until it eventually emerges above sea level.
5) Plate movement carries the island beyond the hotspot and volcanism ceases. As one island becomes extinct, another develops.
95
What happens at the destructive oceanic-oceanic plate boundary?
- When two pieces of oceanic crust collide one is subducted. This may be because one is marginally denser or because it is moving faster.
- As in Oceanic-continental, friction causes EQs and partial crust melting. Ocean trenches again mark the place where the plate is descending.
- Where the volcano erupts on crust which is covered by ocean, islands are formed. They characteristically form a line of curving volcanic islands known as island arcs.
- Over millions of years these island may become major landmasses such as Japan.
96
What were the short term responses to the Bam EQ?
- UK, Germany, USA and Russia sent rescue workers and equipment.
- Over $670 million pledged from several countries
- 16,000 people taken to be cared for in other cities.
97
What were the long-term responses to the Nevado del Ruiz eruption?
- Economic priorities continue to outweigh safety needs
- government preparedness system including detailed warning and evacuation system.
- 3 years later- injury claims made amounting to £40 million but the government were cleared.
98
What were the primary impacts of the Boxing day tsunmai?
- 40,000 more women were killed than men
- 3km inland
- 8000 foreign tourists killed
- 2 million homeless
- Loss of lifestock and farmland
- Destruction of infrastructure
99
What is a dyke?
- Most common form of intrusive feature
- Vertical wall like intrusion of igneous rock
- Discordant
- magma forced through vertical fissures in rocks.
- Vertical intrusion with horizontal cooling cracks.
- Cuts across bedding plane.
- e.g. Swarm of dykes on Isle of Arran 10km long and around 200km wide.
100
What is a Batholith?
- Irregular dome shape from which walls plunge down for many km and are many km wide.
- many have no visible foundations
- Do not align with surrounding rock strata but extend in the same directions of their surrounding mountains
- Formed from magma that has cooled beneath the surface.
- Exposed through continental drift or denudation e.g. Cornubian, SW England.
101
What are the short term economic impacts of an EQ?
- Business lost e.g. Shops and agriculture
- Looting
- Damage to infrastructure= less trade
102
Give the fact file for the Indian Ocean Tsunami?
- 14 countries including Indonesia, Sri Lanka, India, Thailand
- 7:58am, 26th December, 2004
- Magnitude 9.1
- Indo-Australian and Eurasian
- 250,000 dead
- 500,000 injured/missing
- Cost US $9.9 billion
103
What is a geomorphological event?
An event causing harm to people or property, caused by Geomorphological processes e.g. plate tectonic movement
104
Why did the Northeast Honshu tsunami kill so many people?
- Not prepared enough- Fukushima, failure of sea wall
- Complacency and over confidence
- No deadly tsunami since 1933
- False alarms
- Evacuation areas not high enough
- Education in EQs but not tsunamis
- 29 minutes for tsunami to reach coast
105
What is boiling mud?
- Hot springs and mud pools which are often visible when a volcano is approaching the end of its active life or during a dormant period.
- mud is mixed with heated water and causes it to bubble.
- e.g. Rotura, NZ, water is 200 degrees
106
What are the characteristics of basic lava?
- Low silica content
- Low temperature
- Runny viscosity
- In eruptions there is little violence and gases easily escape.
- Regular and continuous eruptions
- Gentle sloped sides
107
What were the long term responses to the Bam EQ?
- President Khatami pledged to rebuild the citadel within two years.
- Seriously considered moving the capital of Tehran as it lies on a major fault.
- In reconstruction, the 1989 Seismic building code was closely followed.
- Some economic and social advancements.
108
What are some of the hazard risks associated with volcanic eruptions?
- Lahar
- Flight and transport disruption
- Landslides
- Loss of lifestock
- Crops destroyed
- Loss of employment
- Damage to infrastructure
- Death
109
How might radon warn of an EQ?
- Some researchers have investigated changes in groundwater radon concentrations.
- radon has a half life of 3.8 days which means it can only be found shortly after being produced in the radiation decay chain. It has been hypothesised increases in radon are the result of new cracks underground.
- many claim it to be unreliable.
110
Give more about vulnerability created by population density?
- Mexico city has 21 million people and is prone to earthquakes
111
What were the secondary impacts of the 2011 NZ EQ?
- 50 to 100 years to completely recover.
- 80% of water and sewage system damaged.
- Psychological- 2013, 80% said lives had significantly changed and 1/3 said they were worse off financially
- Population decline
- No longer hosting rugby world cup.
- Schools forced to amalgamate.
112
What are constantly erupting volcanoes?
- Active
- Usually quiet but can sometimes be violent
- Stromboli, Italian island.
113
Give the fact file of the Haiti EQ?
- Tuesday 12th January, 2010
- Magnitude 7
- 200,000 + dead
- 300,000 + injured
- Estimated £7.6 billion to reconstruct
114
What are intermittent volcanoes?
- Volcanoes which erupt at fairly regular time periods.
| - Mount Asama, Mount Etna
115
What were the secondary impacts of the Haiti EQ?
- Trade, tourism, transport and communications badly affected.
- 1 in 5 lost their jobs because so many buildings were destroyed- clothing industry damaged.
- Large number of bodies meant that diseases, especially Cholera, became a serious problem.
- Hospitals (50+) and schools (1300+) were badly damaged.
116
What are intra-plate EQs?
- twenty to thirty EQs felt every year in the UK
- Most are small and cause no damage.
- largest British EQ was 6.1
117
What were the responses to the Icelandic eruption?
- The IMO worked closely with the national emergency agency, the University of Iceland and the British Meteorological Office and other countries to manage impacts.
- EU prepared for such events and contingency plans in place.
- Handled domestically by countries affected who have infrastructure systems which can cope with such hazards.
118
What was the preparation for the Nevado del Ruiz eruption?
- Limited evacuation drills
| - Not perceived as a threat to human life
119
Give more information about vulnerability created by early warning systems?
- SE Asian Tsunami 2004- no early warning system in Indian Ocean resulted in death of 230,000 people.
120
What were the long term responses to the Boxing day tsunami?
- Indonesian government relocated people straight from refugee camps into new homes. However, construction took a long time because of a lack of material and transport routes.
- $20 million has been spent on a tsunami warning system in the Indian Ocean
- Action Aid offered psychological counselling, housing, boats with motors for fishing communities and rebuilt schools and community centres.
121
How can we measure the risk of an EQ?
```
- The risk to people from an earthquake can be summarised by R= M x P/V
R- risk
M- magnitude
P- population
V- vulnerability
```
122
What were the causes of the Bam EQ?
- Destructive plate boundary of the Arabian and Eurasian plates.
- EQs have killed nearly 200,000 people in the last 30 years
- Buildings largely made of mud brick and didn't comply with 1989 regulations.
- Weather conditions- freezing condition lowered chances of survival.
- Low EQ education- 'What god wills will happen'
- Aid: people from other cities too advantage of supplies; armed bandits looted supplies.
123
Give an example of a lava plateaux?
- Antrum, Northern Ireland
124
What are the MDC EQ case studies?
- Northridge, California USA, 1994
| - Christchurch, NZ, 2011
125
Why will the most severe EQs be located in LDCs?
- 1/3 of largest cities are located in seismic zones
| - LDCs are not as well able to predict, plan and prepare for EQs
126
Give some climatic natural hazards?
- Hurricanes/cyclones/ typhoons
- Tornado
- Flood
- Drought
- Heat waves
- Blizzard
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What were the primary impacts of the the 2011 NZ EQ?
- Aftershocks of up to 5.9
- Killed 185 and injured over 3000
- Power cut to over 50,000 homes
- Liquefaction
- Up to 100,000 buildings damaged and 10,000 destroyed
- 3.5 m tsunami waves
128
Describe what a basic/shield volcano is?
- Formed from free-flowing lava
| - Resulting volcanoes have gentle sides and cover a large area.
129
What were the primary effects of the Mt. Pinatubo eruption?
- Cloud of steam and ash 30km
- Ash fell over 50cm a 20km radius
- Pyroclastic flow ate 700mph
- 1/3 largest eruption of the century
- 200,000 homes collapsed
130
What is a primary impact?
- Direct result of the process itself
131
What occurs at Conservative plate margins?
1) Occur where two plates meet and the direction of plate motion is nearly parallel.
2) No crust is destroyed or created, but there is frequent seismic activity due to the build up of friction which is released as shallow focus earthquakes.
3) they are not associated with active volcanism due to the absence of subduction.
132
What occurs at constructive plate margins?
- Convection currents rise and diverge, creating high temperatures that up dome the crust and tensional forces that pull it apart. As the plates diverge lines of weakness are created, allowing magma to escape.
133
What are sills?
- Magma follows strata as it is forced along horizontally through lines of weakness in the rock.
- It lifts overlying rock creating a flat table like sheet of igneous rock.
- Horizontal intrusions with vertical cooling cracks.
- e.g. Great Whin Sill- 70km thick, Pennines
134
What are some primary impacts of a hazard event?
- Buildings and infrastructure are destroyed
135
Give the causes of the Indian ocean EQ/Tsunami?
- EQ occurred just 30km below the surface
- Wave travelled at 600mph
- Up to 15m high
- Plates lifted along 750m
- Billions of tonnes of water
- Force of 60 hurricanes
- Tsunami travels around world 3x
136
Describe what a lava plateaux is?
- Formed from fissure eruptions. The extensive lava flows are basaltic in nature, so they flow great distances.
137
How can lava diversion help manage the effects of an eruption?
- Bombing- adds air to lava to cool and solidify
- Ditches and barriers to divert flow.
- Cooling-dropping water from helicopters to solidify.
138
What were the secondary impacts of the Bam EQ?
- Loss of tourism from destruction of citadel- reverse multiplier
- 11,000 students killed and 1/5 of the 5,400 local teaching staff were also.
- Situation report released by the U.N disaster Assessment Coordination team noted a rise in post- traumatic stress disorder and depression.
- By 2006, over 50% of men and roughly 15% of women were addicted to opium.
139
How can remote sensing warn of an EQ?
- Observations of changes in the earths crust from satellites which measure changes in electromagnetism and temperatures along fault lines.
- Unproven accuracy
140
What is the Asthenosphere?
- The semi molten layers below the lithosphere on which the plates float.
141
What is the focus?
- The point within the earths crust where the EQ originates.
142
What are the options for EQ preparation?
1) Seismic loading tests
2) Tuned mass dampers
3) Spring base
143
How do tuned mass dampers help prepare for the possibility of an EQ?
- Huge concrete block mounted in the skyscraper, which moves in the opposite direction to the movement of the building caused by strong winds or oscillations in the groud.
144
What are the disadvantages of EQ planning?
- Enormously expensive
| - Requires high levels of education and university skills.
145
What are the disadvantages of the Mercalli scale?
- Subjective
- Qualitative
- No use within isolated, rural areas where damage is limited.
146
What is the Lithosphere?
- Name given to crust and rigid upper layer of the mantle
| - 80-90Km in thickness
147
What is the VEI?
- Volcanic Exclusivity Index- 7 is the highest and most explosive and is measured on a logarithmic scale.
- Mt. St. Helens was a 5.
148
What is the first theory about hot spots?
- Intensive radioactivity
- radioactivity creates a column of upwelling lava known as a 'plume'.
- The plume of rock pushes up; the pressure drops and the rocks become molten melting through the crust above
- As the plates move over the hot spot, the upwelling lava creates a steady succession of new volcanoes that migrate with the plate.
- Some evidence is emerging which casts doubt on this theory.
149
What is a hotspot?
- An area in the mantle from which heat rises as a thermal plume from deep in the earth.
- High heat and lower pressure at the base of the lithosphere facilitates melting of the rock.
150
What were the responses to the 2011 NZ EQ?
- Rescue crew and aid from Japan, US, Uk and Austarlia.
- Four zones- green, orange, white, red- what could be built on?
- Temporary housing
- Water and sewage restored by August
- Canterbury Earthquake Recovery Authority.
151
What are some factors which might determine the severity of an eruption?
- Cost of damage
- fatalities
- Animals/habitats
- Population density
- MEDC/LEDC
- Time of day
- Time of year
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What recent evidence is there to support Wegener's theory of continental drift?
- 1948 (Ewing)- discovery of a continuous mountain range extending 10,000 miles
- Rocks were identified to be fairly new and of igneous origin.
153
What is the crust?
- The solid layer of earth on which we live, made of less dense rock types.
- It is split into seven large tectonic plates and several smaller ones.
- Varies in thickness from 6-10Km beneath mountain ranges
- Abundant in elements
154
What were the primary effects of the Nevado del Ruiz eruption?
- Guali river overflowed
- Natural dam burst
- Mud flows
155
How do vulcanologists traditionally classify volcanoes?
- According to the nature of the eruption
| - The violence of the explosion
156
What are the advantages of the richter scale?
- Quantitive
- Measures size not damage
- Logarithmic scale- increase by 10
- Open ended- no limit
157
What were the responses to Mt. St Helens?
- Helicopters/ rescue missions
| - Millions of dollars to clean up
158
What are the advantages of EQ preparation?
- Saves lives
- Allows buildings to still be used.
- Better management of disasters
- Effective
- EQ monitoring
159
Give some geomorphic and geological natural hazards?
- Volcano
- Landslide
- Earthquake
- Tsunami
160
What were the primary impacts of the Bam EQ?
- 75,000 people homeless
- 85% buildings severely damaged or destroyed.
- 2500 year old citadel, site of international importance, almost completely destroyed.
- Electricity, water distribution and sanitation services were significantly affected or destroyed while all static healthcare centres were irreparably damaged.
- 50% trained medical staff killed.
- Two of the cities hospitals collapsed.
- 29 serious aftershocks followed
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Give some biological natural hazards?
- Floral e.g. hayfever, dutch elm
| - Faunal- e.g. diseases: malaria, Infestations: locusts
162
What are the three types of natural hazards?
- Climatic
- Geomorphic and Geological
- Biological
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What is endogenetic?
- Volcanoes and earthquakes expose continental crust to exogenic denudation processes of weathering and erosion.
164
How can evacuation help manage the threat of volcanic eruptions?
- Only possible with sophisticated prediction techniques
- Requires good infrastructure and organised emergency services.
- 25 mile zone cleared around Mt. St. Helens
165
Describe secondary waves?
- Transverse waves
- Particles vibrate perpendicular to the direction of movement
- Only pass through the crust and mantle
- Absorbed by the liquid outer core.
- Don't pass through the centre of the earth
- Travel 1.7 times slower than p waves
166
How can preparing specifically for lahars help manage the effects of an eruption?
- Can be controlled by dredging river channels to divert the flow of water
- The use of early warning cameras can warn of possible flooding.
167
What is the disadvantage of the Richter scale?
- Expensive equipment
| - Might not show devestation
168
give more information about vulnerability created by construction styles and building regs?
- In Haiti, developers didn't follow building regs which meant they couldn't withstand the earthquake 2011
169
What is a geyser?
- Form when infiltrating water comes into contact with hot rocks below the surface, burning the water to steam and building pressure.
- This is then ejected several metres into the air as a jet of boiling water.
- e.g. 'Old faithful'- Yellowstone, up to 185m
170
Give an example of an acid/ dome volcano?
- Puy region of Central France
171
How does geology impact upon EQ severity?
- Rock type of an area. If the area is solid rock, there is generally less damage than on sands and clays
- On clays liquefaction can occur, where water penetrates between the clay particles creating quick sand like substances into which buildings sink.
- Christchurch, 2011- Liquefaction led to huge amounts of damage to roads and personal property.
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What are some primary impacts of volcanic eruptions?
- Tephra- Solid material of various grain size, from volcanic bombs to ash particles ejected into the atmosphere.
- Pyroclastic flows- hot gases, charged flows
- Lava flows
- Volcanic gases
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What is a lava plateaux?
- Formed after successive eruptions.
- Extensive lava flows across the original landscape.
- e.g. Giant's causeway, Norway
174
Give the background to the Icelandic volcano?
- Constructive plate margin
- Divergence of N. American and Eurasian plates
- Mid-Atlantic ridge
175
Why are pyroclastic flows dangerous?
- High speed avalanches of hot ash, rock fragments and gas that destroy everything in their path (1000 degrees)
e. g. Soufriere hills, Montserrat
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What are the disadvantages of preparation?
- Can cost a lot of money for LDCs
177
What are some secondary impacts of a hazard event?
- People are unable to work and go to school
178
What are the short term social impacts of EQs?
- Casualties and damage to personal property
| - Infrastructure e.g. transport, communications and sewage.
179
Describe a composite cone?
- Classic pyramid shaped volcanoes consisting of layers of ash and lava.
180
What is denudation?
- Long term processes that cause wearing away of Earth's surface, leading to a reduction in elevation and relief of landforms and landscapes.
181
What are the causes of fracking?
- Shale fractures
- Unconsolidated rock
- Water lubricates rocks causing more slips.
- Lorca, Spain, 9 dead
- Contaminates water
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What were the primary impacts of the Haiti EQ?
- main Port in Port-au-Prince was closed after severe damage
- No army and police force collapsed
- 500,000 + homeless
- Only 50% had access to clean water before, now even less.
- Up to 90% of buildings destroyed in some places
- Amputations
- Key official buildings- presidential palace, parliament building, police headquarters and 13 of the 15 government ministries destroyed.
- 3 million effected
183
What are the long term environmental impacts of EQs?
- Important physical and human landscapes may be lost.
184
How can monitoring and prediction help manage the effect of volcanic eruptions?
- Difficult but indicators which might suggest an eruption include... Surface bulging, rise in surface temperature, EQs, rise in gas concentrations
185
Give the background to the eruption of the Nevado del Ruiz
- LDC- Columbia, S.America
- November 1985
- Inactive for over a century
- Series of minor eruptions and tremors
186
Give examples of people/organisations who are against fracking?
- Prof Richard Davies, Durham energy institute
- Centre for climate change research
- Friends of the earth
187
How has Santa Monica, California prepared for EQs?
- Very strict building codes
- UCLA re-building parts of the campus in a $1.3 billion project (FEMA provided $432 million as part of EQ relief.
- Steel beams tested at University of Nevada
188
Why are lava flows dangerous?
- They can cause enormous damage to property, although the rarely pose a threat to human life. They may also seriously disrupt transport and trade links.
e. g. Puu Do crater, Hawaii
189
How did people prepare for the Mt.St. Helens eruption?
- Bulge grew to 122m
- EQs and tremors
- 'Red zone'- 5 mile exclusion zone
- 'Blue zone'- 20 mile exclusion zone
190
What were the secondary effects of the Mt. Pinatubo eruption?
- Ash ruined 1991 and 1992 harvest
- refugee camps and disease
- 1 million farm animals died in the subsequent year
- 3000 farmers abandoned
- 700 deaths
- lahars
191
How might housing quality impact upon EQ severity?
- Poor quality housing is often incapable of withstanding the intense shaking during an EQ which leads to collapse.
- Izmit, Turkey, 1999- Poor migrants live in self-constructed accommodation known as gecekondus which easily collapsed, rapid urbanisation has meant less stringent building quality, 65% buildings constructed without permit.
- Some poorer residents who had afforded legal tower blocks were crushed and had even less chance of survival.
192
What is the mantle?
- Widest layer of earth which is made up of molten and semi molten rock.
- Lighter elements such as oxygen.
193
What were the secondary responses of the California 1994 EQ?
- General public shocked.
- Retrofitting program for all public and old buildings
- Building codes updated.
194
Describe a ash and cinder cone?
- Formed from ash, cinders and volcanic bombs ejected from the crates
- Sides are steep and symmetrical
195
Give an example of a ash and cinder cone?
- Paricutin, Mexico
196
What were the secondary impacts of the boxing day tsunami?
- Risk of famine and epidemic diseases was extremely high immediately following the tsunami- bodies rotting int the tropical heat contaminated food and water sources.
- 15,000 died in refugee camps
- Loss of fishing due to destruction of boats and damage to the ocean floor.
- Decline in tourism
- land disputes
- Emotional and psychological impacts.
197
How might seismic activity warn of an EQ?
- Some scientists claim major EQs are preceded by foreshocks
- While this is true of some EQs, it is not true of all. Some faults are inherently weaker than others.
- Tangshan EQ in 1976 produced no foreshocks resulting in 500,000 deaths.
198
Why are lahars dangerous?
- Mixtures of water, rock, wind and sand flowing down valleys where settlements and populations are concentrated.
e. g. Nevada del Ruiz destroyed Columbian town of Armero
199
What were the primary impacts of the icelandc eruption?
- Fine grained ash plume reached 11,000m into the air.
- 1000 degree lava thrown 15m inti air from 500m fissure.
- Melted glacier
200
What are the landforms associated with constructive plate margins?
- Ocean ridges
| - Rift valleys
201
What can induce seismicity?
1) Storing large amounts of water behind a dam
2) Drilling or injecting liquid into wells
3) Coal mining or oil drilling
- All can lead to a fluctuation in pressure at a fault line.
- Fault line can be re-activated due to increase or removal of sediment
202
What is the core?
- Dense centre layer of the earth divided into solid inner core and molten outer core.
- Temperatures reach over 5000 degrees.
- It is made up of dense elements e.g. iron
203
What are the three classifications of volcanoes?
- Icelandic
- Hawaiian/ Vesuvian
- Krakatoan
- Pelean
204
How has the Wellington Central Police Station in New Zealand been designed in preparation against EQs?
- Built in 1991 and is 20km away from an active fault zone
- Cost $53 million
- Flexible foundations allow the structure to move 40m without damage.
- EQ monitoring system on the roof
- Emergency generator, 60,000 litres portable water capacity, can switch to an alternate sewage facility.
205
How might groundwater levels warn of an EQ?
- Groundwater levels in wells have been known to both decrease and increase rapidly and have been noted as precursors in both China and the USA.
- Groundwater sensitivity to seismic activity can vary greatly depending on the depth of wells and the ruptured fault, so cannot be relied upon for everywhere.
206
What are extrusive features?
- Features found o the surface of the earth including volcanoes
- Geysers, boiling mud, volcanic cones, lava plateaux
207
How did the Hawaiian islands form?
1) In a fixed position under the Pacific plate there is column of up-welling lava which is known as a 'plume'.
2) As the ocean floor moves over the 'hot spot' at about five inches a year, the up-welling lava creates a steady succession of new volcanoes that migrate along with the plate. This has created five volcanic mountain chains and Kilauea is currently the world's largest active volcano.
3) The islands get older the further from Hawaii they are in the chain. One of the oldest was formed between 15 and 25 million years ago while the newest island Loihi is set to surface in around 1 million years.
208
What is a volcano?
- An extrusive feature formed by the accumulation of erupted lava and/ or volcanic ash.
209
Describe the formation of the boxing day Tsunami?
1) Indo-Australian plate subducted below Eurasian
2) Fault ruptures. Western mountain range thrust up 40 feet.
3) Displaced water moves as a series of ripples up to 1m high.
4) Front of wave slows on the land while the back catches up creating a vertical column of water.
210
How do seismic loading tests help prepare for the possibility of an EQ?
- Tests buildings against additional loads and stresses that occur during EQs.
- Engineers need to know the level of the actual or anticipated seismic stresses associated with the direct damage to an individual building subject to a specified magnitude.
- Can be expensive
211
What is a Laccolith?
- Instead of spreading widely as a thin sheet, more viscous lava can arch up into overlying rock into a dome like shape. It is still concordant with the rock layers.
- Sheet intrusion between sedimentary rocks
- Pressure builds causing a mushroom shape to emerge which is then exposed by denudation.
- e.g. Devil's tower, Wyoming- 1200ft high
212
What were the secondary impacts of the Icelandic eruption?
- Ash circulated around the world causing severe travel disruption- cost businesses £130 million a day, 107,000 flights cancelled, 10 million passengers stranded.
- Damage to crops and lifestock
- Flooding with discharges of 2000-3000m3
- Contaminated water and soil
- No human fatalities
213
Give an example of a composite cone?
- Mt Ethna, Sicily
214
What are intrusive features?
- Form when magma welling from the mantle cools and solidifies within the crust. It is forced in between existing rocks.
215
What are some secondary impacts of volcanic eruptions?
- Lahars- Flowing volcanic mud
- Flooding- melting or glaciers and ice caps
- Tsunamis
- Volcanic landslides
- Climatic change- volcanic debris can reduce global temperatures.
216
What is the epicentre?
- the point on the earths surface, directly above the crust, where seismic waves are first felt.
217
What is the second theory about hot spots?
- Proposed in 2003 by Foulger
- Current volcanic anomalies away from plate margins are due to weaknesses in the plates themselves.
- All plates have 'scars' and some are stretched as they are subducted.
- When these vulnerable parts of the crust pass over previously subducted material, they melt easily providing the perfect setting for volcanic activity.
218
What are the advantages of the Mercalli scale?
- Quick, general observations and don't require specialist equipment
- Useful in urban areas to measure impact.
219
What were the short term responses to the Haiti EQ?
- Food for more than two million people a day.
- Relief agencies tried to buy food locally and regionally but were met with difficulties.
- Aid agencies shipped in massive quantities of bottled water and purification tablets.
- UN security council increased the UN stabilisation mission in Haiti by up to 13,000 troops.
- the US has dispatched more than 15,000 military personnel to Haiti
- Makeshift camps set up.
- UN Development programme aimed to temporarily employ 220,000 Haitians to work clearing debris and restoring infrastructure.
220
What does the Seismological society of America say about EQ prediction?
- A valid EQ prediction needs to contain the expected magnitude, epicentre, dates and probability.
- The data must be verifiable and reproducible.
221
What are the advantages of prediction?
- Can give prior warning and save thousands of lives
222
What was the theory that Wegener created?
- German meteorologist
- 1912- stated that the continents were once focused in a super continent which he called Pangaea.
- Although he presented information and evidence for continental drift, he was unable to provide a convincing explanation for the physical processes (tectonic plates).
223
What were the short term responses to the boxing day tsunami?
- People tried to flee
- Bodies buried immediately in mass graves to avoid the spread of disease.
- $7 billion provided by governments and NGOs.
- 5 million had to be housed in temporary shelter with food and water.
- Several months before debris was cleared and reconstruction could begin.
- Warning issued to Africa which saved lives.
224
How did prediction and planning help in the Icelandic eruption?
- Icelandic Meteorological Office monitors earth movements, water conditions and weather and issues warnings.
- Wide range of high tech equipment and sophisticated computer models to monitor seismic activity and predict eruptions.
- MDC experienced in managing volcanoes with a developed warning system e.g. text messages to residents.
