Hazardous Environments Flashcards
Why do people still live in areas at risk of natural disasters?
- Lack of education about hazard
- Cannot afford to move, or not wanting to leave their job
- Optimism about their likelihood of it happening to them, or resigning to their fate
- Areas are built up already, so people will not abandon the area
- They do not want to abandon their friends and family
What are the benefits of living in an area post-volcanic eruption?
- Valubale minerals brought to surface
- Soil is fertilised with minerals by volanic ash
- Geothermal energy from hot springs
- Tourism, such as hot springs
How is a tropical cyclone formed?
- When all conditions are met, rising warm air creates an area of low pressure on the ocean surface.
- This area is filled by surrounding air. The rising warm air cools and condenses to form towering clouds of 12-15km (the eye wall) and rainfall.
- This cool air descends, constantly being replenished, which creates an area of calm and low pressure in the center (the eye).
- The corilosis effect causes the clouds (high pressure) to spin around the eye (low pressure)
What are the characteristics of a tropical storm?
- Very strong winds.
- Torrential Rainfall.
- Storm surges - Sudden rises in sea level
- Areas of low pressure, often 600-700km across.
- Follow the direction of the prevailing wind.
- Lose strength when they reach land, but can replenish once over oceans again.
- Last for on average 10 days.
How are tropical cyclones measured?
- The Saffir-Simpson hurricane scale
- 5 categories based on wind speed
What are the conditions needed for tropical storms?
- Large ocean area over 27C for an extended period of time
- Between 5 and 30 degrees north or south of the equator
- Enough Coriolis force to develop a low pressure centre.
- Low latitude winds blowing in from different directions.
- 74MPH to be considered a tropical storm.
What were the short term impacts of the Mozambique storm?
- Over 800 people died, many more injured.
- Millions of homes were destroyed and people were made homeless.
- Infrastructure like roads, school and hospitals destroyed.
- Mass flooding.
- People without supplies like food and water.
What were the long term impacts of the Mozambique storm?
- Long term homlessness and unemployment due to building damage.
- Disease spread due to cramped living conditions, especially waterborne diseases from flooding like cholera.
- Flooding disrupts food harvests - famine.
What is the distribution of tropical storms?
- Between the tropics and the equator, but not on the equator.
- Occur on oceans.
- Called hurricanes in NA, typhoons in Asia and cyclones in Africa and India.
What are the characteristics/hazards of volcanic eruptions?
- A mountain which magma rises and lava erupts out of.
- Releases slow lava flows.
- Relases ash, which can build up and damage buildings.
- Relases gases which cause respiratory issues.
- Relases fast moving debree flows called lahars.
- Relases very fast superheated clouds of gas, ash and tephra called pyroclastic flows.
- Releases volcanic bombs, which are molten lava rocks which are ejected from the volcano. They can cause forest fires.
What is the distribution of volcanoes?
- They occur alongside earthquakes.
- They are mostly found along destrucive plate margins, but also constructive.
How are volcanic eruptions measured?
- The Volcanic Explositivity Index.
- It is a logarithmic scale from 1-8.
- It measures the volume of ash ejected and how high it reaches.
- It is a very limited scale.
How are volcanoes formed on a destructive plate boundary?
- The friction between the two plates in the subduction zone melts part of the plates, forming magma
- This magma rises and then the lava escapes through cracks in the crust
- This forms a composite cone volcano
How are volcanoes formed on a constructive plate boundary?
Magma rises and lava escapes through cracks in the crust in the mid oceanic ridge created
* It then cools and solidifies, forming a shield volcano
What were the short term impacts of the Montserrat Soufriere Hills Volcano?
- 19 deaths and 100 injured
- Important businesses and infrastructure destroyed
- Half of the island became an exclusion zone
- The main airport closed
What were the long term impacts of the Montserrat Soufriere Hills Volcano?
- Ongoing respiratory issues
- Enviromental damage
- Workforce shortages due to evacuation
- Over dependance on UK handouts
- Industry decimated
What are the characteristics of an earthquake?
- A sudden and brief period of shaking of the ground
- Focus = The most intense area. Epicentre = Area on surface above focus
- They cause alot of damage to buildings, as well as secondary hazards such as Tsunamis and landslides
What is the distribution of earthquakes?
- Occur where volcanoes occur
- Occur along all plate boundaries, especially destructive
- Many in California and Japan
How are earthquakes measured?
- The Richter scale, which is a 10 point logarithmic scale measuring magnitude using a seismometer
- The Modified Mercalli scale which is a 12 point scale measuring the subjective intensity and damage
What happens at a constructive/divergent plate margin?
- Two oceanic plates diverge
- Magma rises inbetween the plates, and lava is able to escape through cracks in the crust
- The lava forms a new crust, which leads to the formation of a mid-ocean ridge and a shield volcano
- Earthquakes can occur here
What happens at a destructive plate margin?
- An oceanic and a continental plate converge
- Since the oceanic plate is denser, it subducts underneath the continental plate
- In the subduction zone, the plates rub together and melt, creating magma, which rises
- Lava is able to escape through cracks in the crust, forming a composite cone volcano
- Earthquakes commonly occur here
What happens at a collision/convergent plate margin?
- Two oceanic plates converge.
- Since they are the same density, neither subducts and pressure begins to build up.
- The pressure releases and the plates buckle upwards, creating fold mountains which are constantly growing.
- Earthquakes can take place here.
What happens at a conservative plate boundary?
- Two continental plates moving at different directions or different speeds.
- They get stuck, and friction between them builds up pressure.
- Pressure releases suddenly as they slip past eachother, causing earthquakes.
What were the short term impacts of the Nepal Earthquake?
- 9000 died, with 23000 injured.
- Thousands were made homeless
- Entire villages were destroyed.
- Infrastructure was completely destroyed.
What were the long term impacts of the Nepal Earthquake?
- Unemployment, and people losing their main source of income.
- Cramped living conditions of temporary shelters led to disease spread.
- Crop fields being rendered unusable caused famine.
- Over 300 aftershocks
How was Nepal prepared for the earthquake?
- They had no early warning systems.
- The people were not educated or drilled.
- The buildings did not have an earthquake proof design
- Transport systems were not designed with aid in mind.
What were Nepals short term responses to the earthquake?
- Search and rescue, including use of helicopters.
- Foreign country and military aid.
- Government offered what little aid they could.
What were Nepals long term responses to the earthquake?
- Educating people about earthquakes.
- New warning systems
- Intercropping for more food.
- Structures built with earthquake proof designs.
What were Japans short term responses to the earthquake?
- 100000 people deployed for disaster relief
- Water and supplies were distributed.
- Shelters were set up in schools and sports centres
- Different companies made communication easier
- Shelterbox, an NGO sent supplies
- Foreign aid helped with search and rescue
How are Japan prepared and what are the long term responses for earthquakes?
- Early warning GIS systems which broadcast warnings
- Drills are often done and people are educated
- Very tight building regulations are undergone
- Remote sensing and hazard mapping are used to indentify areas of high risks
- Rebuilding programmes, which are built to be hazard proof
What are earthquake proof building designs like in developed countries?
- Computer controlled weights on roof to reduce building resistance
- Steel frames designed to sway
- Rubber shock absorbers in the foundations
- Deep foundations sunk into bedrock
