Global Hazards Flashcards
Outline of the global circulation system and the effects of high and low pressure belts
Movement of air around the earth in a specific pattern. Air rises at equator causing low pressure and rainfall when air reaches air it travels north and south and air becomes colder and denser and sinks creating high pressure and dry conditions at 30° north of equ and air rises again at 60°
How does global atmospheric circulation cause extreme weather conditions in different parts of the world
Polar - temp are low
Temperate - moderate summers and winters
Low pressure belt at 60°N/S caused by rising air causing frequent rainfall
Tropical - temps are hot and rainfall is high near the equator where rising air from two cells meet causing high rainfall
Arid - low rainfall hot temp near 30° N/S where two cells from sinking air meet preventing rainfall
What are the extremes in weather conditions associated with wind temp and precipitation in contrasting countries.
Wind - air moving from areas of High to low pressure. This means that atmospheric circulation causes winds making some parts windier than other parts. They are weak in high pressure belts and strong in low pressure belts and when the pressure diff is high, winds are very strong.
Precipitation - occurs when wet rises and cools causing water vapour to condense. Air rises in low pressure belts causing frequent precipitation and intense. High pressure belts air sinks low precipitation.
Temp - equator receives most sun poles receive less sun. Temp are high in 30°N/S and there’s few clouds to block sun energy. Temp in polar regions of thee artic and Antarctic is very low
What is the distribution and frequency of tropical storms and drought and have they changed over time
Tropical storms
Distribution - occur between 5° and 30° north and south of equator they mainly occur in the northern hemisphere in late summer and autumn.
Frequency - they vary each year and in the Atlantic they have increased since 1984 but there’s no overall trend
Droughts
Distribution - droughts change distribution areas at most risk is central and Southern Africa Middle East Australia eastern South America and parts of North America since 1950 there has been more droughts is Asian and Africa and less in America and Russia.
Frequency - has not changed much since 1950 but more severe and frequent drought may occur due to climate change.
What are the causes of the extreme weather conditions caused by El Niño and La Niña causing drought
Changes in global atmospheric circulation (el Nino and La Niña ) means it does not rain for ages in an area.or when high pressure weather systems block depressions
What is the causes, consequences and response of the 2003 heatwave .
Causes - anticyclone situated above wester Europe and air moves anti-clockwise in anticyclones so hot dry air was brought and temps in the uk were higher and rainfall was less and the anticyclone blocked low pressure systems that would normally bring cooler fainter conditions from Atlantic oceans
Consequence - people suffered from heat stroke, dehydration and sunburn and breathing problems caused by air pollution. 2000 people died from the causes of heatwave 20 injured when struck by lightning from heatwave livestock died and water suply decreased
Responses - nhs gave public guidance on how to survive heatwave limits were placed on water usage and they created a heatwave plan on how to minimise heat waves in future
What are the causes consequences and responses of the hurricane Katrina
Causes - temp of Gulf of Mexico sea was 27° so tropical storm can form. Storm formed 200 miles from se Bahamas and moved nw over top of Florida into Gulf of Mexico and as it travelled over storm got stringer and stuck land bringing 200%km/ h winds and 200-250mm of rainfall in Louisiana and a storm surge of 8.5 to Mississippi.
Consequences- 1800 killed. 300000 damaged homes. 3Mill with no electricity Costal habitat damaged.
Responses- 70-80% of New Orleans we were evacuated. Mississippi and Louisiana set up control centres emergency shelters and stock pilled supplies.repaired and rebuilt flood defence costing 14.5 billion new buildings rebuilt on stilts in low lying areas.
How do convection currents move
Lower parts of mantle are hotter than upper parts when lower parts heat up they become less dense and it rises as they move up they cool and sink and this circular motion is called a convection current which cause tectonic plates to move
What happens at a destructive plate boundary
Oceanic and continental plate move towards each other and when they meet oceanic plate subducts under continental plate causing magma under to melt and force it’s way up to the surface creating volcanoes
What happens at a constructive plate boundary
Plates move away from each other and magma rises in between and cools and condenses causing volcanoes
What happens at a collision plate boundary
Continental crust move towards each other forcing themselves up creating fold mountains
What happens at a conservative plate boundary
The plates move past each other either in same direction but diff speed or diff direction and the edges are rough causing pressure to build up and. eventually they give in causing earthquakes
What are hotspots and how do they form volcanos
They are a bit of crust that is hotter than usual this is caused when magma moves upto surface creating a large flow of heat. The magma may break through creating a volcanic eruption. Hotspots remain stationary but crust above it move creating a chain of volcanic islands
How does the tectonic plates cause earthquakes
Destructive - tension build up as plates get stuck
Collision - tension build up when plates are pushed
Constructive - tension builds along cracks as plates move away
Conservative - tension build up when plates get stuck from grinding against each other
What is a deep and shallow focus earthquake and how are they caused
Deep - caused by previously subducted crust focus of 70-700km under surface
Shallow - caused by tectonic plates moveping near or on the surface focus of 0-70km under surface
Deeper do less damage
