Tectonics Flashcards
Context of Montserrat Volcano?
- 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
Economic Impacts of Montserrat Eruption? (negative then positive)
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
Social Impacts of Montserrat Eruption? (negative then positive)
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
Environmental Impacts of Montserrat Eruption? (negative then positive)
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
Responses to Montserrat Eruption? (short then long term)
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
Management of the Montserrat Eruption?
- 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
Context of Mt. St. Helens Eruption?
- 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
Economic Impacts of Mt. St Helens Eruption? (negative then positive)
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
Social Impacts of Mt. St Helens Eruption? (negative then positive)
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
Environmental Impacts of Mt. St Helens Eruption? (negative then positive)
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
Responses to Mt. St Helens Eruption?
- 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
Management of Mt. St Helens Eruption?
- 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
Context of the L’Aquila Earthquake?
- 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
Economics Impacts of L’Aquila Earthquake?
- 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
Social Impacts of L’Aquila Earthquake?
- 300 deaths, mostly by collapsing buildings
- 1500 injured
- 70,000 made homeless
- aftershocks hampered immediate response
- people moved away in search of work
Environmental Impacts of L’Aquila Earthquake?
- 1000km^2 affected by surface ruptures, rockfalls and landslides
- broken water pipe near Paganica caused a landslide
- habitats disrupted
Responses to L’Aquila Earthquake?
- 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
Management of the L’Aquila Earthquake?
- 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
Context of the Kashmir Earthquake?
- 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
Economic Impacts of Kashmir Earthquake?
- estimated $5bn cost
- while villages and thousands of homes destroyed (80% of town of Uri) (within 25km radius, 25% collapsed)
Social Impacts of Kashmir Earthquake?
- 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
Environmental Impacts of Kashmir Earthquake?
- 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
Responses to the Kashmir Earthquake?
- 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
Management of the Kashmir Earthquake?
- no local disaster planning
- no buildings designed to withstand EQs
- communications and infrastructure were poor
- i.e. very little planning, prevention or risk mitigation
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
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
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
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
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
Name one example of each type of volcano
- Dome: Puy De Dome
- Caldera: Aira Caldera
- Shield: Mauna Loa
- Fissure: Laki Fissure System
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
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
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
What are hotspots caused by and give an example of landform created?
Superheated magma plumes
Hawaii (volcanic islands)
Primary and Secondary Waves?
PRIMARY:
- travel through solids and liquids
- longitudinal
- fastest
SECONDARY:
- travel through solids
- transverse
- very damaging due to shearing effect
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)
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
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
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
Define a hazard?
A potential threat to human life or property
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
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
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
Building for EQs?
- designed to withstand EQs e.g. shock absobers
- construction laws in EQ prone countries have become stricter
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
Building for Tsunamis?
- open, raised foundations and strong materials can withstand
- tsunami walls sometimes effective e.g. Hokkaido in Japan
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
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
