Comp 1 Topic 1- Hazardous Earth Flashcards
What conditions are needed for tropical cyclones to form?
Sea temperature is above 26.5 degrees
Wind shear is low between higher and lower parts of the atmosphere.
Where is the most common place for cyclones to form?
Between 5 and 30 degrees north and south of the equator any further form here and the water isn’t warm enough.
What time of year do cyclones form in the Northern and Southern hemisphere?
NORTH- June to November
SOUTH- November to April
How does a Cyclone form?
Warm, moist air rises and condensation occurs which releases a lot of energy. The rising air creates a low pressure area, which increases surface winds. The earths rotation reflects the wind and causes the cyclone to spin. They move west. As they move away from the equator they move either north or south as they are trapped in the westerlies. They get stronger from energy in water. They lose energy when they move over land or cold water. Climate change means more seas are above 26.5 degrees
Describe the eye of the cyclone.
Its up to 50km across and caused by descending air. There is very low pressure, light wind, no clouds, no rain and a high temperature.
Describe the eye wall of the cyclone
It surrounds the eye, theres spiralling, rising air. Very strong winds around 160km per hr, storm clouds, torrential rain and a low temperature.
Describe the edges of the cyclone
The wind speed falls, the cloud become smaller and more scattered, the rain becomes less intense and the temperature increases
What are the physical hazards of Tropical cyclones?
- High winds - can reach 250km
- Intense rainfall - potentially releasing trillions of litres of water
- Storm surges - low pressure and high waves cause rise in sea level
- Coastal flooding - Flooding happens as a result of storm surges
- Landslides- hills unstable from rain
What are the impacts on people of Tropical Cyclones?
- People drown in the strong currents created by floodwater and storm surges
- Winds can destroy homes
- High winds and floodwater carry debris, can kill
- Electricity supplies can be cut off
- Flooding causes sewage overflows which contaminate water supplies
- Diseases can spread due to lack of sanitation
- shortage of food in developing as animals and plants
- Unemployment Increase because businesses are damaged or destroyed
- damaged roads make it difficult for aid and emergency vehicles
What are the impacts of Tropical cyclones on the environment?
- Trees are uprooted which can destroy wooded habitats
- storm surges erode beaches and damage coastal habitats
- landslides deposit sediment in rivers and lakes which can kill fish and other wildlife
- oil refineries and chemical plants on the coast can leak into the environment
Describe how a country can be Physically, Economically or Socially vulnerable
P- low lying coastlines are vulnerable to storm surge flooding as well as large waves caused by the high winds.
Areas in the path of tropical cyclones hit more frequently, steep hillsides increase the risk of landslides.
E- many people depend on agriculture which is badly affected
- people may not have the insurance to cover repairing damages caused by cyclones
-Economic impact is much higher in developed countries as everything costs lots of money
S- buildings are poor so are damaged easier
-health care isn’t good so they struggle to treat everyone
-little money for flood defences or emergency teams
-its harder to rescue people due to poor infrastructure
What is forecasting and how does it help prepare and respond to Tropical Cyclones
- when and where the cyclone will hit
- they can monitor the path of the cyclone and see where it is going to hit
- the cyclones magnitude can be measured by its windspeed.
- it gives people time to get supplies, protecting their home and evacuate
What is Evacuation and how does it help prepare and respond to Tropical Cyclones
- An alert will give people the time to evacuate
- governments can plan an evacuation route
- successful evacuations can reduce number of deaths
- emergency services can train
What are Defences and how does it help prepare and respond to Tropical Cyclones
Defences can be built along the coast to prevent damage storm surges, they can be built to withstand flood water (stilts)
This will reduce the number of buildings destroyed so fewer people will be killed, injured, made homeless and unemployment
Describe the core
Inner (solid) outer (liquid) made or iron and nickel. At the centre is very dense. The temperature inside the core ranges from 4400-6000 degrees
Describe the mantle
Made of silicon based rock
The part of the mantle nearest the core is quite rigid.
Asthenosphere is semi molten. Very top is rigid.
1000-3700. Hotter towards core cooler the further away
Describe the crust
Made of silicon based rocks
Two types of crust. Continental and oceanic
Continental crust is thicker and less dense
Oceanic is thinner and more dense
How do tectonic plates move?
They float on the mantle
Radioactive decay of some elements in the mantle and core generate heat.
When lower parts of the asthenosphere heat up they become less dense and slowly rise
As they move towards the top of the asthenosphere cool down ,they become less dense and sink
The circular movements of semi molten rock are called convection currents
They create drag on the base of the tectonic plates which cause them to move
How do winds transfer energy from the equator to the poles?
1) The sun warms the earth, transfers heat to the air, it creates a low pressure belt as the air rises it condenses forming clouds, rain.
2) The cool dry air moves out 30degrees north and south of equator
3) the cool air sinks 30 degrees north and south, creating a high pressure belt with cloudless skies and very low rainfall
4) the cool air reaches the ground surface and moves as surface winds either back to the equator as trade winds or to the poles as westerlies.
5) at 60 north and south of the equator the warm surface winds meet colder air which is forced upwards, it forces cold air to rise creating low pressure and frontal rain
6) some air moves to equator, some to poles
7) at poles cool air sinks creating high pressure, the high pressure air is drawn back as surface winds
How is heat transferred by ocean currents?
Currents are mass movements of water which transfer heat energy from warmer to cooler regions.
Surface currents are formed by winds and help transfer heat away from the equator. E,g. Gulf stream transfers heat from caribbean to west Europe.
Deep ocean currents are driven by differences in water density, when water freezes it increases the salt content in the water around it increasing the density as it gets denser it sinks causing warmer water to flow over it creating a current, this process repeats. (Thermohaline circulation)
How do pressure belts cause global atmospheric circulation cause variations in climate?
Arid- sinking air from Hadley and ferrel cells meeting causes high pressure and prevents rainfall. Rainfall is low and temperatures are high
Tropical- Rising air from the two Hadley cells meeting causes low pressure and lots of rainfall. Hot and rainfall is high
Polar- Sinking air from polar cells create an area of high pressure at the poles, temperatures are low all year and very little rainfall.
How was the earths climate in the past?
During the quaternary period global temps has shifted between cold glacial periods that last for 100,000 years and warmer interglacial periods which last for periods of 10000
