Tectonics Flashcards

1
Q

Context of Montserrat Volcano?

A
  • Soufriere Hills Volcano erupted in June 1997
  • composite volcano along destructive margin between NA and Caribbean plates
  • EQ’s, lahars and small erupions began two years before the main event
  • pyroclastic flows started just before the eruption
  • 4.5 million m^3 of material was released over 20 minutes
  • pyclastic flows came within 50m of the airport
  • subsequent eruptions in following months with airport destroyed in September
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2
Q

Economic Impacts of Montserrat Eruption? (negative then positive)

A

Negative:

  • loss in property and investment value totalled £1bn
  • over 20 villages and 2/3 of homes on the island destroyed
  • loss of tourism and business
  • schools, hospitals, the airport and port destroyed

Positive:
- tourism to volcano now picking up due to renewed interest

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3
Q

Social Impacts of Montserrat Eruption? (negative then positive)

A

Negative:

  • 19 dead and 7 injured
  • hundreds lost their homes
  • fire destroyed many more buildings than the eruption including many govt buildings (police stations, etc.)
  • 2/3 of the population have left since (1/3 to the UK), population decline has decimated the local economy

No positives

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4
Q

Environmental Impacts of Montserrat Eruption? (negative then positive)

A

Negative:

  • large areas covered with volcanic material, Plymouth (the capital) covered by 12m of ash and mud
  • vegetation and farmland destroyed

Positive:
- volcanic ash has improved soil fertility

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5
Q

Responses to Montserrat Eruption? (short then long term)

A

Short-term:

  • people evacuated from the South to safe areas in the North, starting two years before the event
  • shelters built to house evacuees
  • temp. infrastructure build e.g. roads and electricity distribution
  • UK provided $17mil in short-term emergency aid
  • local emergency services started search and rescue operations

Long-term:

  • risk map created and exclusion zone (south of island) created
  • UK provided £41mil in long-term aid to rebuild infrastructure and houses
  • Montserrat Volcano Observatory established
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6
Q

Management of the Montserrat Eruption?

A
  • scientists studied the volcano in the 80’s but little attention was paid to their findings
  • no disaster management plan meaning responses were far too slow
  • in the 90’s, key infrastructure was built in high risk areas, further hampering the response when it was destroyed
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7
Q

Context of Mt. St. Helens Eruption?

A
  • Mt. St Helens erupted in May 1980
  • part of the Cascade Mountains of Washington
  • on a destructive margin between the Juan De Fuca and NA plates
  • composite volcano
  • from March 1980: small EQ’s, a bulge appeared, ash and steam released
  • on the day, a large 5.1 EQ following by the eruption
  • 600km^2 fan-shaped area north of the volcano was affected - where almost all vegetation and buildings were destroyed
  • pyroclastic flows, lahars and floods caused immense damage
  • 540 million tonnes of ash distributed over 57000km^2
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8
Q

Economic Impacts of Mt. St Helens Eruption? (negative then positive)

A

Negative:

  • total costs to businesses and individuals: $1.1bn
  • over 200 homes and cabins destroyed and many more damaged
  • airports closed for two weeks - 1000 flights cancelled
  • vast amounts had to be spent clearing ash from routeways, in Yakima (135km from volcano) alone, $2.2mil was spent
  • 27 bridges, 25km of railways and around 300km of roads were destroyed
  • river traffic and shipping disrupted - 30 ships stranded due to sediment in rivers
  • timer industry badly affected

No positives

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9
Q

Social Impacts of Mt. St Helens Eruption? (negative then positive)

A

Negative:

  • 57 killed, mostly due to respiratory issues
  • hundreds lost their homes
  • unemployment briefly rose 10x but quickly normalised
  • social and recreational facilities destroyed
  • emotional stress caused

No positives

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10
Q

Environmental Impacts of Mt. St Helens Eruption? (negative then positive)

A

Negative:

  • 240km^2 of forest destroyed
  • 7000 big game animals and many thousand birds and small animals killed
  • 12 million young salmon killed
  • sediment dumped in Spirit Lake raised water level by over 60m
  • water quality temporarily reduced

Positive:
- improved soil fertility, but very few farmers in area

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11
Q

Responses to Mt. St Helens Eruption?

A
  • coordinated by FEMA, assisted by US military

Short Term:

  • face masks distributed to prevent ash inhalation
  • emergency shelters set up

Long Term:

  • ash clean-up operations - 900,000 tonnes of ash cleared off infrastructure
  • shipping channels cleared of sediment and new channels cut to restore shipping to normal
  • 45,0000 aces of land replanted
  • water supplies monitored to ensure they were not contaminated
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12
Q

Management of Mt. St Helens Eruption?

A
  • in March, USGS set-up a 42-hour monitoring system (seismic data, bulge growth, ground temp, gas emissions)
  • reports issued daily
  • issued warnings to locals and designated hazardous zones
  • in March, exclusion zone created and 2000 evacuated
  • However, could still not accurately predict when the eruption would occur, even on the day
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13
Q

Context of the L’Aquila Earthquake?

A
  • occurred in April 2009
  • L’Aquila is a city in central Italy with a population of 70,000
  • major fault lines run underneath L’Aquila
  • close to the destructive margin between Eurasian and African plates
  • 6.3 on the Richter scale
  • depth of 5km, epicenter near L’Aquila
  • several aftershocks up to 5 on the Richter scale
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14
Q

Economics Impacts of L’Aquila Earthquake?

A
  • costed $15bn in total
  • thousands of building destroyed including hospitals and the cathedral
  • bridge near Fossa collapsed and several water pipes were broken
  • fires caused further damage to collapsed buildings
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15
Q

Social Impacts of L’Aquila Earthquake?

A
  • 300 deaths, mostly by collapsing buildings
  • 1500 injured
  • 70,000 made homeless
  • aftershocks hampered immediate response
  • people moved away in search of work
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16
Q

Environmental Impacts of L’Aquila Earthquake?

A
  • 1000km^2 affected by surface ruptures, rockfalls and landslides
  • broken water pipe near Paganica caused a landslide
  • habitats disrupted
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17
Q

Responses to L’Aquila Earthquake?

A
  • camps setup for homeless with water, food and medical supplies
  • ambulances, fire engines and army sent in to help rescue
  • cranes and diggers used to remove rubble
  • international teams with rescue dogs sent in
  • 12,000 rescue and support workers
  • mortgage payments and utility bills were suspended
  • new town build to replace L’Aquila with 4500 new buildings housing 12,000 in 6 months
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18
Q

Management of the L’Aquila Earthquake?

A
  • there were some management strategies in place but they were not very effective
  • strict building regs. for new buildings to withstand EQs, but some were still poorly built and collapsed e.g. San Salvatore Hospital
  • some monitoring was in place - but it is very difficult to predict EQs, this may have caused locals to be complacent
  • Civil Protection Department trained to help with rescue operations
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19
Q

Context of the Kashmir Earthquake?

A
  • occurred on 8/10/2005
  • Kashmir is in Northern Pakistan on the destructive margin between Indian and Eurasian plates
  • 7.6 on the Richter scale
  • 16 mile depth with epicenter close to Muzafrabad
  • caused by plate movement creating a 75km fault
  • 30,000km^2 area damaged
  • almost 1000 aftershocks up to magnitude 4
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20
Q

Economic Impacts of Kashmir Earthquake?

A
  • estimated $5bn cost

- while villages and thousands of homes destroyed (80% of town of Uri) (within 25km radius, 25% collapsed)

21
Q

Social Impacts of Kashmir Earthquake?

A
  • 80,000 deaths, mostly by building collapse (13th highest on record)
  • hundreds of thousands injured
  • 3 million made homeless
  • water and electricity cut off
  • landslides blocked roads, cut off infrastructure and buried people
  • diarrhea and other disease spread via dirty water
  • winter meant many people freezing to death and hampered responses
22
Q

Environmental Impacts of Kashmir Earthquake?

A
  • landfalls and rock slides throughout region (notably in Muzzafrabad)
  • Jhelum valley landslide was the biggest, 1km wide and reaching 2km
  • ground shifted by up to 5m
23
Q

Responses to the Kashmir Earthquake?

A
  • help didn’t reach many areas of days or weeks (people had to be rescued by hand)
  • tents, blankets and medical supplies provided by not to many remote areas
  • FRC and ERRA setup to coordinate with NGOs and govts
  • international equipment and aid brought in e.g. helicopters, dogs and rescue teams
  • 40,000 relocated from Balakot
  • govt money provided to individuals to help rebuilt
  • training to make buildings more EQ resistant
  • new health centers set up
24
Q

Management of the Kashmir Earthquake?

A
  • no local disaster planning
  • no buildings designed to withstand EQs
  • communications and infrastructure were poor
  • i.e. very little planning, prevention or risk mitigation
25
Differences between two types of crust?
OCEANIC: - newer, 6-10km thick, 2.9g/cm^3, basalt CONTINENTAL - older, 30-70km thick, 2.7g/cm^2, granite
26
Evidence for tectonic theory?
GEOLOGY: - areas of South America and African have rocks of the same age and composition and the distribution matches if the continents are fit together - match age and distribution of mountain ranges in Scotland and Norway FOSSIL RECORDS: - distribution of fossils e.g. glossopteris matches up if continents and fit together - highly improbable these species migrated across oceans LIVING SPECIES: - many living organisms can be found across many continents e.g. earthworks across Asia, N. American and NZ CLIMATOLOGY: - evidence suggests past climates were different, thus located at different latitudes - glacial sitrations match distribution of glacial deposits across Antarctica, S. America, African, India and Aus - large coal deposits e.g. Birmingham formed under tropical conditions suggest we were once at equator PALEOMAGNETISM: - alternating plate polarity and earth's polarity reverses every 200,000 years
27
Type of margin; example; landforms; EQ's?; Volcanoes?
Constructive; Eurasian and NA; MOR/Rift Valleys; EQs; Volcanoes Destructive C-O; Nazca ans SA; fold mts/trenches; EQs; Volcanoes Destructive O-O; Pacific and Philippine; trenches/island arcs; EQs; Volcanoes Destructive C-C; Indo-Aus and Eurasian; fold mts; EQs Conservative; NA and Pacific; low ridges; EQs
28
For each type of lava, silica content, viscosity and temp.?
BASALTIC: - low silica (52%) - low viscosity - over 950C ANDESITIC: - med silica (52-63%) - med viscosity - 750-950C RHYOLITIC: - high silica (>63%) - high viscosity - less than 750C
29
Types of intrusive volcanic activity?
BATHOLITHS: - formed when large chambers of magma cool underground - forms huge domes e.g. Sierra Nevada - only becomes visible due to erosion SILLS: - formed when magma flows between layers of sedimentary rock - cools quickly with vertical cooling cracks DYKES: - formed when magma flows vertically into gaps in rock and cools with horizontal cooling cracks
30
Name one example of each type of volcano
- Dome: Puy De Dome - Caldera: Aira Caldera - Shield: Mauna Loa - Fissure: Laki Fissure System
31
Hot Springs?
- places heated groundwater emerges at the surface - heated by coming close to an area of recent intrusive activity - temp varies for 20-90C - high mineral content due to hot water being capable of holding high amounts of dissolved soils - e.g. Rio Hando in Argentina
32
Geysers?
- type of hot spring where steam is periodically ejected from surface - restriction in plumbing pressurizes recently heated water - forces its way to surface under pressure - when water escapes the sudden drop in pressure causes rapid boiling and ejection of water from geyser - sinter keeps the plumbing system watertight - e.g. Old Faithful in Yellowstone
33
Boiling Mud Pools?
- another type of hot spring - forms in areas with very fine soil where the water mixes with the soil to form boiling mud pools - can contain brightly colored mud due to minerals like iron and sulphur - e.g. in Yellowstone
34
What are hotspots caused by and give an example of landform created?
Superheated magma plumes Hawaii (volcanic islands)
35
Primary and Secondary Waves?
PRIMARY: - travel through solids and liquids - longitudinal - fastest SECONDARY: - travel through solids - transverse - very damaging due to shearing effect
36
Love and Rayleigh Waves?
Both can only travel near the surface and are slower than P and S waves LOVE: - travel through solids - transverse - damaging due to shearing effect RAYLEIGH: - travel through solids and liquids - move surface in rolling motion (like ocean waves)
37
Richter scale?
- measures magnitude - no upper limit - amplitude is logarithmic - increase in value represents x30 increase in energy released - 1/2 would not be felt - above 7 is major
38
Mercalli scale?
- measures the impacts of an earthquake - measured using observations - scale is 1-12, 1 being detected only by instruments and 12 being total destruction
39
Tsunamis?
Large waves caused by the displacement of large volumes of water (by earthquakes) In open ocean: 500-900km/hr; 200km wavelength; 1m amplitude Close to land: 80km/hr; less than 20km wavelength; several m amplitude Just before tsunami reaches coast water draws-back and hits with great force, although does not travel far inland
40
Define a hazard?
A potential threat to human life or property
41
Prediction of EQs?
- impossible to predict exactly but can be clues e.g. small tremors, rocks cracking, rats fleeing nests - warning systems can detect P waves and give a little warning e.g. Japan's EQ early warning system - likelihood can be determined using past data to assess risk
42
Prediction of Volcanoes?
- possible to roughly predict due to tiny earthquakes or changes in shape - allows for evacuation e.g. 60k evacuated from Mt. Pinatubu in 1991 - even with warning some will not want to leave homes or will distrust scientists
43
Prediction of Tsunamis?
- reliant on EQ detection systems and knowledge of whether even will trigger tsunami - warning centres around the world e.g. NOAA - gives people time to evacuate as long as communication systems are sufficient
44
Building for EQs?
- designed to withstand EQs e.g. shock absobers | - construction laws in EQ prone countries have become stricter
45
Building for Volcanoes?
- cannot be built to withstand lava - can be build to support weight of falling ash - possible to create diversion channels for lava e.g. rubble barriers around Mt Etna
46
Building for Tsunamis?
- open, raised foundations and strong materials can withstand - tsunami walls sometimes effective e.g. Hokkaido in Japan
47
Planning and education?
- future developments planned to avoid the riskiest areas - emergency services can train to prepare for disasters e.g. FEMA - govt can plan evacuation routes - govt and NGOs can educate people how to react e.g. in Japan at school VERY COST EFFECTIVE
48
Why does developmental level affect the severity of impacts?
- little money to prepare or setup warning systems - poorer quality buildings - more likely to be damaged] - infrastructure is poorer - harder to rescue and recover - healthcare is poorer, harder to treat large casualty numbers - many depend on agriculture and will be severely affected by the event However, in HICs the economic impact is higher and there is more economic activity and higher value buildings