Plate Tectonics (Factor of EQ, Hazards of EQs, risks and benefits of volcanoes) KQ2 Flashcards
Factors affecting extent of EQ damage
1) Magnitude
2) Level of Preparedness
3) Population density
4) Distance from Epicenter & depth of focus
5) Type of Soil
6) Time of Occurrence
How does Level Of Preparedness affect damage of EQ?
Def: amt of preparations takes by authorities and citizens
-Makes EQ more manageable and people are better prepared.
e.g. Tohoku EQ, 9.0 mag, 2011, Japan - 28,000 deaths
Haiti EQ, 7.0 mag, 2010, Carribeans - 300,000 deaths
How does magnitude of EQ affect damage of EQ?
Greater Magnitude, larger extent of damage and destruction
How does Population density affect damage of EQ
Def: Number of people living in the affected area
- Sparsely populated: less affected
- Densely populated: heavily affected, mass casualties and damage
How does distance from epicenter affect damage of EQ?
Epicenter Def: Directly above focus on surface
- Closer the area to epicenter, the more severe the damage
How does depth of focus affect damage of EQ?
Focus def: Origin of EQ in crust
-Affects magnitude of EQ
1) Deep Focus
- 70 - 700km below surface
- Seismic waves take longer time to reach surface = smaller impact
- Most energy lost to surroundings
- Lower magnitude
2) Shallow Focus
- 0-70km of crust
- Seismic waves reach land surface more quickly
- Less energy loss
- Higher magnitude
How does timing of EQ affect damage of EQ?
- Time determines where people are and what they are doing
- Affects chance of survival
-Night: Sleeping = trapped = more casualties - Day: Active = Quick responses = more survive
e.g. 2,400 deaths aft 1999 Sun Moon Lake EQ in Taiwan aft midnight.
How does type of soil affect damage of EQ?
-Loose, unconsolidated soils amplify seismic wave vibrations = greater mg
- Saturated and unsettled sediments liquify under vibrations = sinking of infra (Liquifaction)
e.g. 2011, Christchurch, NZ.
Tsunamis
Def: Large sea-waves formed by high-energy tectonic activities displacing large masses of water.
1) Seismic energy displaces huge volumes of water
2) Starts at heights of less than 1m, length of 100-150km and speeds of 800km/hr
3) When reaches shallower waters = greater friction = slow down = height increase
4) Reach heights of 15m and speeds of 30-50km/hr
5) Sea may retreat to fill void caused by movement of seafloor.
Tsunami example
2004, 9.2 mag EQ, Indian ocean.
-Tsunami damaged coasts of 12 countries
- heights of up to 40m, reaching 10km inland
Effects of Tsunamis and EQs
1) Disruption of services
2) Destruction of Infra
3) Destruction of property
4) Fires
5) Landslides
6) Loss of Lives
How are services disrupted during tsunami/EQ?
Def: Disruption of essential services such as electricity, gas and water, affecting large areas
- snap pipes, break cables, affect communication and power networks.
Disruption of services (Tsu/EQ) example
Kobe EQ, Japan, 1995
-Damaged pipes, and transmission lines, affecting power gas and water
-Affected 1.4 million residents
-Burst gas pipes caused city wide fires
Fires during EQ/tsu
- Gas pipes burst, petrol gas escapes
- Exposed cables may spark, setting flammable materials on fire
- Fire can spread easily and quickly over large areas.
- Causes injury and death
Fires (EQ/tsu) example
Kobe EQ, Japan, 1995
-Toppled appliances sparked fires
- Firemen unable to manage fires due to no water supply, strong winds, extensive fuelling and fast spreading of fires.
How are landslides caused during EQ/tsu
Def: Rapid downslope movement of soil, rock and vegetation debris from a slope
- Vibrations destabalise soil
- slopes weaken and sediments slide
- Can reach speeds of 40 - >80km/h and stretch for a few km wide
-Mudflows occur when soil is saturated
Landlisde (EQ/Tsu) example
Peru EQ, 1970
-Destabalised Mount Huascaran
-Landslides >160km/h
-Flattened town of Ranrahirca
-Killed, >18,000 people and only 200 survived.
Destruction of property during EQ/tsu
- Widespread destruction to homes
- Displaces people
- Restoration and reconstruction costly
Destruction of property (EQ/tsu) Examples
Tohoku EQ, Japan, 2011
-Tsunami extended 10km inland
- Extensive structural damages and thousands displaced and left without homes
Destruction of Infra During EQ/tsu
-Causes cracks and damage to infra
- Transportation to and within region affected (inaccessible)
Destruction of Infra (EQ/tsu) examples
Kobe, 1995
- Inaccessible
Tohoku, 2011
- USD$300 billion in repairs
Loss of Lives
- Hazards threaten lives of people
- Important for people to be prepared and take precautionary measures to minimise damages.
Tohoku EQ, Japan, 2011
-Mag 9.0
- 28, 000 deaths
- 155,000 homes lost
- Nuclear power plant crippled
- Tsunami reached 10km inland
- USD$300 billion in damages
Haiti EQ, Carribeans, 2010
-Mag 7.0
- 300, 000 deaths
- 1.3 million left homeless
Sichuan EQ, China, 2008
- Mag 8.0
- 100, 000 deaths
- 374, 000 injured
- 15 million evacuated
- 5.36 million buildings collapsed
- Major landslide occured
Risks of Volcanoes
1) Massive destruction by volcanic materials
2) Landslides
3) Pollution
4) Short term effects on weather
Massive destruction by volcanic materials
- Lava, pyroclasts and volcanic bombs
- High temps of 500 - 1400c
-Destroy and burn property
-Low silica lava / pyroclastic flows move rapidly and destroy anything in path
- Inhalation of ash and gases cause injury and death
Damage from volcanoes examples
Kilaueu Hawaii, 1983
- Constant eruptions damage houses and transport infra
Landslides due to volcanic activity
- Structural breakdown on volcanic cone
- Debris obstruct rivers = flooding
- Block Roads = hinder access
- Bury Villages and farmlands
Volcanic landslide examples (Lahars)
Nevado del Ruiz, South American Andes Mt.s, 1985
-Pyroclastic flow mixed with glacial ice, forming lahars
- Engulfed town of Armero and killed >20,000 people
Pollution caused by Volcanic activity
1) Ground pollution
- Ash and pyroclast eventually settle, suffocating crops and burning surrounding
- Fine Ash block sunlight, prevent photosynthesis, killing crops
2) Air pollution
- Release of gases, CO2, SO2, CO, harmful to people and env
- Cause respiratory problems for people and animals
-Fine ash carried over long distances pollute env on larger scale
Pollution from volcanic activity example
Icelandic Volcano, 2010
- Posed threat to airspace (air+ash pollution)
- Airspace closed over Europe and flights delayed
- 1.2 million passengers affected, USD$1.8 million lost
Volcano effects on weather
-SO2 reacts with water vapour and chemicals in atmosphere to form sulfate aerosols
- Aerosols reflect incoming shortwave radiation = temporary global cooling
Volcano Effects on weather examples
e.g. Eruption of Mount Tambora, Indonesia, 1815
- Dropped global temperatures by 1.7c
e.g. Eruption of Mount Pinatubo, 1991
- Dropped global temperatures by 0.4c
Benefits associated with Volcanoes
1) Fertile soil
2) Precious stones and minerals, building materials
3) Tourism
4) Geothermal energy
Fertile Soil (vol)
- Breakdown of lava, rocks and ash from fertile volcanic soils
A: Richest soils on earth = favourable for agriculture
L: Takes thousands of years for volcanic rocks to break down and release minerals/nutrient
Fertile Soil (vol) examples
e.g. Java & Bali, Indonesia
- Soils support large rural populations over many decades
- Soils support wide cultivation of crops (tea, coffee, rice)
Precious Stones and Minerals, building materials provided by volcanoes
1) Volcanic rocks rich in precious stones and minerals (Carbon under high heat, pressure and cooled in magma)
A: Used for industrial tools, scientific research and commercially sold as Jewellery
L: Extraction only after millions of years. Volcanic rocks have to erode and break down.
2) Volcanic rocks contain compounds useful for producing building materials and daily items
Precious stones and minerals, building materials produced by volcanoes examples
e.g. Volcanic rocks of Kimberly, South Africa,
- Richest source of diamond in the world
e.g. Java, Indonesia
- Sulfur compounds collected and used to make matches, fertilisers and refined sugar
Tourism from volcanoes
-Offer opportunity for various activities (hot springs, camping, scenery etc)
A: Volcanic areas usually rich in history- tourists interested to learn more.
Tourism from volcanoes examples
e.g. Ruins of Pompeii, Italy
- Buried by layers of ash from mount Vesuvius in 79CE
- Unearthed archaeological site reveals well preserved buildings, poetry and mosaics
- Attracts >3million visitors per year
e.g. Taiwan & New Zealand
- Built facilities above hot volcanic rocks to provide Geothermal Spas
Geothermal Energy from volcanoes
- Derived from earths crusts
- Groundwater heated by hot rocks, expands and rises as hot water and steam.
A: Utilised to run turbines and produce electricity
Geothermal Energy examples
e.g. Iceland
- 70% of homes powered by volcanic steam
