Topic 1 - Global Hazards Flashcards
Outline the global circulation system.
- What are the effect of high and low pressure belts?
GCS: The world-wide system of winds by which the necessary transport of heat from tropical to polar latitudes is accomplished.
OUTLINE - of high and low pressure belts.
TROPICAL RAINFORESTS
LOW PRESSURE BELTS (aka depressions) - How do low pressure belts cause rainy/tropical climate zones?
- At Equator Sun warms the Earth which transfers heat to the air so air becomes less dense and rises as convection currents.
- Rising air creates a low pressure belt.
- As this air rises it moves out and away from equator, cools and condenses to form clouds and convection rain. (CCCR) (this forms the ITCV - Intertropical convergence zone).
DESERTS -
HIGH PRESSURE BELTS (aka anticyclones) - how do high pressure belts cause dry/arid conditions?
- At 30 degrees north and south of the equator, high altitude winds blow air from the equator.
- This cool air now sinks and warms to create high pressure belt regions which causes the clouds to evaporate leading to clear skies and low rainfall.
- Because there are no clouds and no rainfall, there is very dry climate around these high pressure belts and deserts such as the Sahara desert is found around here.
- Trade winds now blow this air back to the equator and to the ITCZ.
These differences in atmospheric pressure is what causes day to day changes in weather.
What is meant by wind?
Large scale movements of air caused by differences in air pressure.
What are the four different climate zones/regions around the world?
How does the global circulation system cause extreme weather in these parts of the world?
- Temperate climate zones
- Polar climate zones
- Tropical climate zones
- Arid/dry climate zones
**Tropical climate zones; (0 to 35 degrees from equator)
At tropical climate zones temperatures are HOT all the times and RAINFALL is HIGH.
This because here, Sun’s rays hit the ground at an angle of incidence and so meaning heat is concentrated in a small area so air warms and rises, and CCCR (this rainfall is known as convection rainfall) - this is why tropical rainforests for along the equator.
**Temperate climate zones (60 degrees N/S from equator).
At temperate climate zones the temperature is moderate during the winter and summers.
This is because the Sun’s rays hit the surface at a lower angle of incidence so heat is spread over a larger area making it cooler. So warmer air rises and CCCR meaning at temperate climate zones there is rain all through out the year (more frequent).
**Subtropical zones (30 degrees N/S from equator)- including arid and dry;
At these climate zones rainfall is very low and temperatures are ver warm/hot.
This is because they receive the highest solar radiation especially during their summer due to the high angle of incidence of the Sun’s rays. This warms the sinking air from the two cells meeting air and it, and so clouds evaporate and clear creating a drier climate because there are no clouds so no rainfall. (S-W-E-C).
**Polar climate zones (66 - 90 degrees from equator)
At polar climate zones the temperatures are low all year round.
At polar climates the temperatures are low all year round.
In polar regions the Sun hits the Earth with the lowest angle of incidence meaning heat is spread over the largest area so temperatures are very low.
At polar regions there are 6 months of night so no light. High pressure due to S-W-E-C means there snowfall is low creating polar deserts.
During 6 months of light, when Sun is up snow covers the ground and ground becomes white. This white snow reflects the heat making it cooler. This is known as the Albedo Effect.
How does global atmospheric circulation cause high/low temperatures?
High pressure and Low pressure belts are caused by the global atmospheric circulation system.
Link this to high and low temperatures.
At high pressure belts what happens?
S-W-E-C - warmer
At lower pressure belts what happens?
C-C-C-R - More humid conditions when near equator
OR
closer to the poles lower temperatures due to less heat from equator - more dense S-W-E-C and freeze, albedo affect reflect heat so even lower temperatures.
How does the global circulation system cause precipitation?
Near equator at low pressure belts, air is heated so becomes less dense and rises - CCCR to cause convection rainfall.
Away from equator at high pressure belts, air cools and becomes denser so S-W-E-C so less clouds so less rain.
How does the global circulation system cause wind (making some parts of the Earth windier than others)?
Large scale movements of air caused by larger differences in air cause strong wind.
Small scale movements of air caused by smaller difference in air pressure at is what causes weaker winds.
Large scale winds associated w low pressure belts.
Smaller winds associated w high pressure belts.
Outline distribution and frequency of tropical storms and drought, and whether these have changed over time.
TROPICAL STORMS:
- Formation:
- Tropical storms develop when sea temperature is 27 deg celc or higher.
- Trade winds must be present
70m
-5 and 20 deg from equator. - This warm ocean temperature means there is a lot of warm/moist air to cause extreme precipitation via RCCCR (warm air rises, cools and condenses releasing huge amounts of energy and precipitation.
- As the air rises it creates areas of low pressure, this increases the surface winds.
- At the same time the Earth’s rotation deflects the path of these winds, this is called the Coriolis effect, causing the cluster of cumulonimbus clouds (thunderstorms) to spin.
- These spinning storms continue to get stronger due to energy from the warm water so in turn the wind speed also increase.
- This causes tropical storms to form.
EXTREME WEATHER CONDITIONS ASSOCIATED WITH TROPICAL STORMS:
1 - Extreme winds found in the eye of tropical storms (formed at low pressure created due to RCCCR).
- Inside the eye of tropical storms wind speeds are more than 250 km/h (this can destroy and damage buildings.)
2- Extreme torrential rain
- Distribution; NOT CHANGING. occur 5 deg and 30 deg North and South of the equator (because any further than this from the equator, the water isn’t warm enough).
They occur in the Northern hemisphere. - Change over time/Trend; number of tropical storms have increased since 1984 but there is no overall trend over the last 130 years.
- Frequency; the number of tropical storms varies each year.
DROUGHTl
- Formation/causes;
- Changes in atmospheric circulation such as El Nino or La Nina can mean there is little to no precipitation and anticyclones block depressions - these are what cause rain.
- Distribution;
Highly variable with no particular pattern; areas most at risk are central and Southern Africa, Middle East and North America. - Change over time/Trend; varied year to year but overall has not changed much since 1950.
Outline the causes of extreme weather conditions associated with tropical storms.
1 - Extreme winds found in the eye of tropical storms (formed at low pressure created due to RCCCR).
- Inside the eye of tropical storms wind speeds are more than 250 km/h (this can destroy and damage buildings.)
2- Extreme torrential rain (large amounts of warm moist air being sucked into the centre of the storm RCCCR).
- This torrential rain can cause flooding and mudslides.
Outline the causes of the extreme weather conditions of El Niño/La Niña leading to drought (how does El Niño/La Niña cause drought?)
How does El nino cause drought?
Pressure rises in the Western Pacific and falls in the Eastern Pacific.
This causes trade winds to reverse.
So higher pressures (so drought - SWEC) over W pacific and lower of E pacific (so wetter).
How does La Nina cause drought?
- Normal GHS are made more extreme.
- Trade winds blow more strongly from eastern to western pacific.
- More cold water here rises - so air above cools, condenses to form heavier rainfall in the Western Pacific and more droughts in the East.
Check case study flashcards.
- Typhoon Haiyan
- UK 2022 Heat wave
The processes that take place at constructive, destructive, conservative and collision plate boundaries as well as hotspots.
PLATE BOUNDARIES:
Constructive - Plates move apart from each other due to convection current creating a gap. Magma from the mantle fills this gap and cools to become a solid creating new crust.
Destructive - oceanic and continental plates move towards each other, and denser oceanic plate is subducted by continental plate and destroyed.
Conservative - 2 plates moving sideways past each other, in the same direction but at different speeds. Smtimes get stuck due to jagged edges causing pressure to form an earthquake.
Collision - 2 continental crusts move towards each other, collide and form mountains.
Hotspots - an area of the Earth’s mantle from which hot plumes rise upward, forming volcanoes on the overlying crust.
How does the movement of tectonic plates cause shallow focus and deep focus earthquakes?
DEEP FOCUS. Occur at destructive plate boundaries - and explain - link to plates getting stuck and pressure being created.
SHALLOW FOCUS - where focus 0km - 70km below Earth’s surface.
Found at constructive plate boundaries - explain.
How does the movement of tectonic plates cause shield and composite volcanoes?
- Collision plate boundaries:
2 continental crusts move towards each other, collide and form mountains.
Tectonic Hazard Case study:
'’On 22 Feb 2011 a 6.3 magnitude earthquake hit the city of CC in NZ’’
CHRISTCHURCH EARTHQUAKE:
- Causes - caused by conservative plate boundaries between Pacific and Australian plate.
- Shallow focus Earthquake only 5m deep.
CONSEQUENCES
- social 185 ppl killed, 80% ppl say lives changed significantly in a survey.
-
RESPONSES
- Building officers assessed safety of 72k buildings
- 80% roads restored by August 2011.
How technological developments can have a positive impact on mitigation in areas prone to a tectonic hazard of your choice (earthquakes).
- Building design
- Early warning systems
- Prediction
- Buildings being assessed, eg 72k after Christchurch Earthquake;
good bc safety, bad bc not all.
- Early warning system - lasers and seismometers monitor Earth’s movements and predict EQ.
Good bc predicts and ppl can prepare eg trains slow down reducing collateral damage eg CC where 185 ppl were killed, bad bc requires internet and not all ppl have that.
