Geography - hazardous environments Flashcards
What is a hazard
An event that threatens, disrupts and has the potential to injure, kill life, destroy properties and settlements, cause socioeconomic destruction or environmental degradation.
Types of hazards: Climactic
Storms, floods, draught
Types of hazards: geological
Volcanoes, Earthquakes, Landslides
Types of hazards: Technological
Nuclear explosions, traffic accidents, pollution
Types of hazards: biological
Disease, fires, pests
Tropical cyclones - causes
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Tropical storms - Distribution
- 5 degrees to 30 degrees north and south of the equator
- Tropical storms can’t be formed at the equator because that’s where the Coriolis force is at zero (Coriolis force is strongest at the poles (earth spins the slowest there), and weakest at the equator (earth spins the fastest)- meaning it won’t be able to spin and form a tropical storm
Tropical storms - effects and characteristics
- Very strong winds: can destroy trees, crops, buildings, transport link, power supplies etc.
- Storm surges: sudden rises in sea level associated with the very low pressure which allows the sea to ‘expand and its level to be pulled up higher; can cause particular damage to coastal areas.
- Torrential rain - heavy rain, can cause inland flooding and often triggers landslides and mudslides.
Tropical storms - measurement
Saffir Simpson scale
- Minimal: Damage to unanchored mobile homes, vegetation and signs. Coastal road floods. Some shallow flooding of susceptible homes. Wind speed: 74- 85kmph, storm surge: 4-5m.
- Moderate: significant damage to mobile homes and trees. Significant flooding of roads near the coast and bay. Wind speed: 96-110, storm surge: 6-8m
- Extensive: structural damage to small buildings. Large trees down. Mobile homes largely destroyed. Widespread flooding near the coast and bay. Wind speed 110-130, storm surges 9-12m
- Extreme: Most trees blowdown. Structural damage to many buildings. Roof failure on small structures. Flooding extends far inland. Major damage structures near the shore. Winds: 131-155, storm surges: 13-18.
t. Catastrophic: All trees were blown down. Some complete building failures. Widespread roof failures. Flood damage to lower floors less than 15 feet above sea level. Wind speed: more than 155, storm surge: greater than 18.
Tropical storms - impacts
Short term impacts
Physical - damage to property
Social - number of people killed or injured disruption of communities and their normal ways of life; decline in quality of life
Economic - destruction and disruption of businesses, transport links and services
Environmental - landslides; soil erosion; upset ecosystems, prolonged flooding
Primary and secondary hazards/impacts:
Primary- torrential rain, storm surges, high winds.
Secondary- high cost economically in repairing damage caused, the spread of waterborne diseases - water supply lines may be damaged or contaminated, loss of homes, personal possessions(cars) and transport lines blocked by landslides- disruption of businesses etc.
Plate boundaries and how they create earthquakes and volcanoes - Conservative
- When two plates move parallel to each other
- Plates move either in different directions or different speeds
- Friction between the two plates creates pressure in between which causes fracturing of the rock, eventually causing an earthquake.
- Example: San Andreas fault
Plate boundaries and how they create earthquakes and volcanoes - constructive/divergent
- When two plates move away from each other
- Magma or molten rock rises up to the top where the mantle was melted to fill the gap.
- As they cool down, they solidify into crust.
- Small fractures in the newly formed crust could cause earthquakes
- If magma is buoyant enough, it can rise through and form volcanoes which could lead to eruptions of magma through them.
Plate boundaries and how they create earthquakes and volcanoes - destructive
- When plates move against each other and collide head-on.
- If both plates are continental plates, neither of them subduct as they are both buoyant, compression causes them to form mountains.
- If one plate is continental and one is oceanic, since the oceanic plate is denser, it subducts and sinks below the corresponding continental plate.
- Pressure build, rocks crumble and fractures, causing earthquakes
- As the oceanic rock subducts and sinks underneath the continental rock, the mantle is melted, giving a pathway for magma to rise through, hence creating volcanoes
Volcanoes and Earthquakes: distribution
- Mostly distributed along plate boundaries.
- Concentration of volcanoes along the destructive plate margins that fringe the Pacific ocean.
- Also concentrated along the African rift valley, which coincides with a constructive plate margin.
Volcanoes - characteristics
- Lava flows - few lava flows reach beyond 10km so there usually aren’t many casualties. Lava flows however mainly destroy farmland, buildings and lines of transport
- Ash - this may be thrown into the air during a violent eruption. Often ash is carried in the wind and therefore it can affect a large area. This happened over much of Europe in 2010 when a volcano in Iceland erupted. The ash cloud brought air travel to a halt. The further away from the volcano. The thinner will be the deposits of air. Ash causes much damage by simply blanketing everything, from crops to roads. Roofs of buildings will collapse if the weight of the deposited ash is great. Air thick with ash can asphyxiate humans and animals.
-Gas emissions - sulphur gases are not the only type emitted during an eruption. Other gases emitted, notably carbon dioxide and cyanide, can also kill. Being dense, they keep close to the ground. Particularly lethal are what are known as pyroclastic flows. E.g. Mount Pinatubo injected about 15 million tons of sulfur dioxide into the stratosphere. Sulfur dioxide reacted with water to form a hazy layer of aerosol particles.
Over the course of the next two years, strong stratospheric winds spread these aerosol particles around the globe.
