Hazardous environment Flashcards
Earthquake formation
kinetic energy is created from lithosphere movement
friction created by the subduction of plates or sliding converts kinetic energy into elastic potential energy
tension is eventually released in the form of earthquakes
Tectonic plate movement
convection currents in molten lava(asthenosphere) causes movement in the lithosphere(crust)
Constructive boundary
aka divergent
plates move apart
magma wells up to fill the gap, forming new crust
e.g. mid-atlantic ridge
Conservative boundary
aka transform
plates slide past each other
e.g. north America + pacific
Collision boundary
Continental plates collide
mantle can’t be destroyed so plate is pushed up and creates a fold mountain
e.g. Eurasian + Indio-Australian (Himalayas)
Destructive boundary
aka convergent
oceanic and continental plates collide
denser oceanic plate is subducted under the mantle of the continental plate
e.g. Nazca + South American
Primary earthquake impacts
physical- landslides and collapsed buildings, broken water and ruptured gas mains(fire)
economic - ports closed,
social - homelessness, casualties
Secondary earthquake impacts
physical - tsunamis, aftershocks and fires
economic - rebuilding
social - PTSD
political - government response
Earthquake characteristics
focus - where earthquake originates
epicentre - point on earth’s surface above the focus
7 Factors affecting earthquake impacts
geology - strength of bedrock relief depth of focus magnitude duration vulnerability of the area population density
Composite cone volcano
formed at destructive plate margin
has steep sides
made of alternative layers of lava and ash
forms andesitic lava
high amounts of gas and ash
violent eruptions
andesitic lava
viscous(high silica)
- thick and sticky
acidic
Shield volcano
formed at constructive plate margin
has gentle slopes
low, wide cone
form basaltic lava
less violent, effusive eruptions
basaltic lava
thin and runny
non-acidic
flows over long distance
9 Impacts of volcano
- lava flows
- destroyed buildings, roads and crops
- contamination of water
- ash - asphyxiate people
- landslides
- lahars
- gas emissions - CO2, cyanide and sulphur
- pyroclastic flows
- tsunamis
lahars
mudflow or debris flow composed of a slurry of pyroclastic material, rocky debris and water that flows down side of volcano
pyroclastic flows
dense, fast-moving flow of solidified lava pieces, volcanic ash and hot gases
4 tropical cyclone conditions
- deep layer of humid, warm and unstable air >27°C
- supply of energy(heat and moisture) from the surface of the sea(ocean water >27°C)
- circulatory air motion due to earth spinning - Coriolis force
- small changes in wind speed and direction with increasing altitude - wind shear
Tropical cyclone formation
- air rises quickly, drawing moist air up from the ocean, leading to strong winds
- warm air spirals upwards, cools and condensed, forming large cumulonimbus clouds
- the clouds form eye wall where inside there is low-pressure and dry conditions near the surface
- the Coriolis force, prevailing winds, ocean current and wind shear influence the direction
Characteristics of tropical cyclone
- strong winds- up to 120km/h
- intense rainfall from cumulonimbus clouds(200-250mm per couple hours)
- lasts for 10 days
- 32-48km wide eye wall
- overall 600-700km wide
Primary cyclone impact
social - casualties from collapsed buildings, disruption of community
physical - storm surges, tree damage, rainfall
economic - loss of business and infrastructure
environmental- landslides, mudslides, damaged ecosystems, prolonged flooding
Secondary cyclone impact
social- PTSD and disease
physical - replanting and repairing coastal ecosystems
economic - cost of repairs, rebuilding businesses
Storm surge
Sea rise due to low pressure and high winds from cyclone
causes sea to expand by pulling water level up
Mercalli scale
measure of the damage created by an earthquake
subjective
Saffir-Simpson scale
measure of hurricane’s maximum sustained wind speed
1-5 rating
estimates potential property damage
Richter scale
quantitative measure of the magnitude of an earthquake- amount of energy released
logarithmic- x10 each time
based on info gathered by seismograph
Moment-magnitude scale
measure of an earthquakes magnitude based on its total seismic moment release
logarithmic
6 Reasons for living in hazardous area
- tourism
- geothermal energy
- fertile soils (volcanic ash)
- minerals (diamond)
- lack of money to move
- lack of education
Prediction
GIS and remote sensing
- maps analyse land to see where hazards are likely to happen
seismometers
-monitor earth tremors
risk assessment
-distribution, frequency and scale
Planning: building resistance
interlocking steel frame
- sways during earth movement
rubber shock-absorbers to absorb earth tremors
foundation sunk into bedrock
building materials are fire resistant
computer controlled weight on roof to reduce movement
window shutters to prevent glass shattering
quick access for evacuation
preparation
warning systems - seismometers, computers and satellites transmit alarms education - evacuation drills construction emergency supplies and services
