Global hazards Flashcards
Natural Hazard
- An extreme natural event or process that can lead to loss of life and/ or damage to property and severely disrupts human activity
What causes a tectonic hazard?
- The movement of the Earth
What causes a Climate Hazard?
- Processes in the atmosphere
Weather
- The day to day conditions of the atmosphere involving, for example, temperature, precipitation and wind
Climate
- The average weather conditions recorded over a period of at least 30 years
Atmosphere
- The air above our heads
- Mass of swirling gases, liquids and solids, such as CO2, O2, water vapour and droplets and ash
Circulation
- Circular air movements called cells.
- These cells all join together to form the overall circulation of the Earth’s atmosphere
What are the 3 circulation cells?
- Hadley Cell
- Ferrel Cell
- Polar Cell
What is wind?
- The movement of air from an area of high to low pressure
- The greater the difference in pressure, the greater the winds
Trade winds
- Winds that blow from high pressure belts to low pressure belts
- Used by trading ships to sail
- Mt. Washington has winds up to 372 km/hp
Katabatic winds
- Caused by air flowing downhill
- In Antarctica, large sloping ice sheets contribute to wind speeds of over 320 km/h
Jet stream
- Winds that are high in the atmosphere
- Speeds of 225 km/h recorded on Mr. Everest
Tropical Storms
(winds)
- Very strong rotating winds
- Start smaller but develop into strongest winds ever recorded
- Die out when they reach land
- Highest speed recorded was 408km/h on Barrow Island in Hurricane Olivia in 1996
The Albedo effect
- How much a surface reflects or absorbs the Sun’s rays
- The more reflective, the less heat it can hold
What happens during El Niño?
(bullet points)
- Trade winds in the western Pacific Ocean weaken, stop or reverse
- The piled up water around Australia and Indonesia moves its way back towards the eastern Pacific Ocean
- Water in eastern Pacific Ocean gets 6-8 degrees warmer than usual
What happens during El Niño?
(high pressure, low pressure etc.)
High pressure- Australia
Low Pressure- Peru
Rainfall- South America
Drought- Australia
Flooding- Peru
Trade winds- Weaken, stop or reverse
What happens during a normal year?
(bullet points)
- Trade winds blow westwards over Pacific Ocean, pushing warm water from Peru to Australia
- In the eastern Pacific, off the coast of Peru, the thermocline is especially low
What happens during a normal year?
(high pressure, low pressure etc.)
High pressure- South America
Low Pressure- Australia
Rainfall- Australia
Drought- N/A
Flooding- N/A
Trade winds- East to West
What happens during La Niña?
(bullet points)
- Doesn’t always come after an El Niño year
- Unusually cold sea surface temperature in eastern tropical Pacific
- More extreme version of a normal year
What happens during La Niña?
(high pressure, low pressure etc.)
High pressure- South America
Low Pressure- Australia
Rainfall- Australia
Drought- Peru
Flooding- Australia
Trade winds- East to West
Thermocline
An abrupt temperature gradient in a body of water such as a lake or ocean, above and below the thermocline the water is at different temperatures
Drought
A period of below average precipitation where the abnormally dry weather leads to a shortage of water, which can have a negative effect on vegetation, animals and people over a large area
Arid
- Lacking moisture
- Very dry
Causes of droughts
Human causes:
- Global warming
- Soil erosion
- Deforestation
- Irrigation
- Population increase
- Urbanisation
Physical causes:
- El Niño
- Climate change
- Position of ITCZ (Inter- tropical convergence zone)
ITCZ meaning
Place where the Hadley cells meet
Tropical Storm
- Areas where air is rising and causing extreme low pressure on the Earth’s surface
- This creates powerful spiralling winds that last 6-14 days with wind speeds of over 120km/h
What are tropical storms called in the Atlantic and Pacific?
Hurrricanes
What are tropical storms called in the Northwestern Pacific?
Typhoons
What are tropical storms called in the Indian Ocean and the Southwestern Pacific?
Tropical cyclones
Inner core
- Solid metal
- Radius of 1220km
- Made up of iron and nickel
- Hotter than the surface of the Sun at 6000 degrees Celsius
- Pressure of other layers compresses inner core
Outer core
- Made up of iron and nickel
- 2300km thick
- 4400 degrees celsius
- Less pressure on it so the metal that it is made up of is liquid
Mantle
- Split into lower mantle (mesosphere) and upper mantle (asthenosphere)
-2900km thick (84% of Earth’s volume) - Made up of magnesium, iron, silicon and oxygen
- Between 1000 and 3700 degrees celsius so in the upper mantle, the solid is mostly putty
Crust
- Thinnest layers of the Earth
- Oceanic crust- Made from balsamic type rocks rich in magnesium and aluminium
- Continental crust- Made of granite type rock, rich in silico and aluminium
Tectonic plates
- Plate tectonics is the theory that Earth’s outer shell is divided into several plates that glide over the mantle, the rocky inner layer above the core
- The plates act like a hand and rigid shell compared to Earth’s mantle
Plate Boundary
- The line where different plates meet
- There are 4 types of plate boundaries: Constructive, Conservative, Destructive and Collision
Earthquake
- The sudden release of energy that is the result of the movement of layers of rock in the Earth’s crust
How do earthquakes happen?
- Rough edges of plates try to move past each other and get stuck, building up energy, which is then released when the plates slip
- Energy is released as seismic waves
How are earthquakes measured?
(most known technique)
Richter Scale:
- Open- ended scale
- Measures magnitude of a tremor
- Uses seismometer
- Logarithmic scale ( so a 2 is 10x more powerful than a 1 and a 3 is 100x more powerful than a 1 etc.)
How are earthquakes measured?
(less known technique)
Mercalli Scale:
- Based on what people felt/ saw during the earthquake
- Subjective scale
- Uses Roman Numerals
Richter Scale
(Advantages)
- Quantitative data
- Objective data
- Accurate
- Factual
Richter scale
(Cons)
- Computer/ Seismometer could malfunction
Mercalli Scale
(Pros)
- Cheaper
- Qualitative data
Mercalli Scale
(Cons)
- Not factual
- People may have different opinions and experiences with earthquake based on where they were when it happened
- Takes longer to get data
- Subjective
How does a tsunami form?
1- Eurasian plate gets dragged down/ subducted by the Pacific plate grinding under it
2- It gets pulled down so much that it springs back up when an earthquake happens
3- This causes a four-mile deep mass of water to thrust upwards
4- When the dome collapses, strong waves of around 3 feet high travel outwards at a blistering speed, creating a tsunami
5- The tsunami gets taller as it gathers more water as the waves get closer to the coast
