Global Hazards Flashcards

where does weather happen

troposphere

why does temperature decrease as altitude increases

because you get further from the ground as the sun releases softwave radiation but when it hits the earth it gets transferred into longwave radiation and in that process on the ground heat is released

why is the equator hot

the suns rays hit it in a smaller more concentrated area making that area hotter

why are the poles cold

the suns rays hit a larger area so are less concentrated and the heat is spread

what is the global circulation system

world wide system of winds responsible for transport of heat from tropical to polar latitudes and 80% of heat is transferred this way

how does air move

from areas of high pressure to low pressure

what happens in low pressure areas

air rises because it is less dense than the air around it and as it rises it cools which causes water vapour in the air to condense as cold air can’t hold as much water vapour as warm air so the water vapour is forced to change state. the condensed water forms clouds which leads to precipitation

what happens in high pressure areas

air sinks because it is more dense than the air around it and as it sinks it heats up which causes water to evaporate to form water vapour which means no clouds form and there is no precipitation

why do winds blow anti-clockwise in the northern hemisphere

the coriolis effect deflects winds to the right

what does the global circulation system look like

POLAR CELL

low pressure

FERREL CELL

high pressure

HADLEY CELL

low pressure

HADLEY CELL

high pressure

FERREL CELL

low pressure

POLAR CELL

how can global atmospheric circulation cause extreme winds

it causes areas of high and low pressure when the land heats up faster than the sea so there is a high pressure gradient over a short distance so winds can be extremely strong and fast as they try to equalise the pressure difference

what are normal conditions in the pacific ocean

easterly trade winds push warm water towards australia in the west

there is warm sea and low pressure in australia so the water evaporates to form water vapour and rises resulting in rain

when warm water is pushed towards the west the cold water from the deep ocean rises up next to south america causing high pressure to air sinks and there are no clouds and no rain so no rain in south america

what happens during el nino

easterly trade winds weaken or reverse so warm waters move towards south america

south america has intense low pressure leading to heavy rainfall and flooding making the wet peruvian boy

australia has intense high pressure due to colder water leading to no rain and droughts

what happens during la nina

easterly trade winds strengthen pushing more warm water towards australia

australia has extreme low pressure leading to heavy rainfall and possibility of floods

south america has extreme high pressure leading to no rain and droughts

how are tropical storms formed

when there is **low pressure** and the sea is above **26c** water from the warm ocean evaporates which becomes water vapour and rises due to the low pressure. as it rises it cools and condenses releasing **latent heat** which causes the water to evaporate again to become water vapour and rise even further causing rain and cumulonimbus clouds

why has wellington new zealand got an average wind speed of 29 km/h with gusts of up to 248 km/h

the land heats up faster than the sea so the land has low pressure and the sea has high pressure and the winds move from the sea to the land to equalise the pressure. also because of the mountain range around wellington winds are funnelled in and their speeds increase

why did hurricane ima have wind speeds of up to 300km/h

there was a very big pressure difference of 274mb between the eye and eyewall causing a very high pressure gradient over a short distance and fast winds trying to equalise the pressure

what is the weather associated with tropical storms

strong winds and heavy rainfall

how many tropical storms are there

on average there are 80 tropical storms per year with the most occuring in the western pacific as it is a large ocean with warm water

how have tropical storms changed over time

number of tropical storms has increased in the atlantic since 1995 and the average hurricane now releases 70% more energy than the average hurricane 30 years ago which could be linked to global warming

how do el nino and la nina affect the amount of tropical storms

during el nino winds high over the atlantic are stronger than normal causing less storms there as they blow apart however in the eastern south pacific there are more during el nino and less during la nina

what is a drought

a period of time with abnormally dry weather leading to a shortage of water which can have a negative effect on vegetation animals and people over a large area

what is a human cause of drought (o)

**soil erosion**: overgrazing when cows eat too much means the soil is less well bound together so it is exposed to wind erosion which blows away soil meaning grass cannot grow there so the grass and soil are not able to hols and store water so all the water there evaporates and the soil dries up completely causing a drought

what is a human cause of drought (d)

**dam building**: the gibbe III scheme in ethiopia of building a dam on the river omo caused there to be less water in kenya so lake turkana dries up meaning they have to rely on water from the rain which there is not enough of causing a drought

what are the physical causes of drought

**intertropical convergence zone ITCZ**: is a low pressure belt which moves north and south to the tropics of cancer and capricorn bringing rain but if it doesn’t move as far northward or southward to reach some of the driest areas they face droughts

**el nino**: brings descending air and high pressure over indonesia and australia causing droughts

extreme weather non uk: what happened during The Big Dry

the big dry was a drought period in australia between 2002-2009 and it was the driest period australia had experienced in 125 years. areas in the east such as queensland and new south wales suffered most with the lowest rainfall ever recorded there experienced

the big dry case study facts

in bundarra in new south wales the temperature was 36c in january when it is normally 30c in january and there was 10mm of rainfall per month when there is normally 50-80mm of rainfall per month

what are the physical causes of the big dry

during el nino the trade winds over the pacific ocean weaken meaning less warm water is brought from south america so there is high pressure there meaning there is no rain and a drought

what are the human causes of the big dry

farmers in the murray-darling river basin took too much water because their local government in new south wales allowed them to meaning there was not enough water for farmers further downstream to use for crop irrigation and for their animals

evaluate the causes of the big dry

the physical causes had a greater influence on the big dry because they caused the problem and although the human causes worsened the problem even without the farmers over extracting water el nino made the drought extreme and last for 7 years

what were economic consequences of the drought

water bills rose by 20% in 2008 to encourage people to use less water as there wasn’t enough in the murray-darling so people would use less if it meant they had to pay more money

10000 people directly employed by the cotton industry were affected as cotton requires a lot of water to grow effectively but there was not enough so they had to reduce their number of farmers

how did eutrophication cause lower water quality

farmers near the murray darling used excess fertiliser to help their plants grow however excess nutrient from it washed into the water causing algae to grow on the surface taking oxygen from the water and blocking sunlight reaching other life in the water. this caused problems for the fish in the sea which did not have enough oxygen to breathe and the plants which could not grow which continued until no life was possible and the water quality was reduced

what was a long term response to the big dry

a multimillion dollar desalination plant was built in sydney as it is a big city with lots of people and water shortages to turn seawater of which there is a lot of into drinking water

what is a flash flood

a sudden localised flood due to heavy rain

how extreme was the Boscastle flood

boscastle received 70mm of rainfall on August 2004 in two hours whereas on average it usually receives 70mm in the whole of August and the flash flood was a 1 in 400 year event

what were the physical causes of the Boscastle flood

there had already been above average rainfall for the previous two weeks in Boscastle 2004 so the ground was already saturated meaning it could not absorb any more rainfall so the 70mm of rainfall in 2 hours flowed quickly over the surface as surface runoff to the rivers (especially due to the steep land around Boscastle as it is in a valley) instead of slowly through the ground causing the flood. also Boscastle is the meeting point of three rivers valency Jordan and paradise which caused huge volumes of water from the rivers overwhelming the village and causing a flash flood

what were the human causes of the Boscastle flood

the sewer systems and drains weren’t big enough for the volume of water suddenly in Boscastle causing them to flood

assess what was worse the human or physical factors in causing the Boscastle flood

the physical factors were worse because they caused the flood and even though the human factors made the flood worse they could not alone cause it

what is the distribution of earthquakes and volcanoes

tectonic hazards occur in bands that follow the edges of plate boundaries and earthquakes and volcanoes are found on all plate boundaries

what happens at a destructive boundary (convergent)

two plates of different densities push together and the denser plate (oceanic) will subduct meaning it sinks below the less dense (continental) plate

what happens at a collision zone (convergent destructive) boundary

two plates push together or converge but they are both the same density (both continental) so they just collide and push up against each other with no subduction

what happens at a constructive (divergent) plate boundary

two plates are separated and pulled away from each other in opposite directions (iceland mid atlantic ridge) allowing magma from the mantle to reach the surface through volcanic ridges

what happens at a conservative plate boundary

plates slide past each other in the same direction at different speeds or in opposite directions but they will snag which builds up pressure until they finally jolt past each other (san andreas fault)

what hazards are created at a destructive plate boundary (convergent)

as the denser plate sinks into the mantle it rubs and causes friction which melts the plate and creates magma which can lead to volcanic eruptions as the magma reaches the surface. earthquakes are also felt due to the stress caused by the friction of the plates such as in the 1991 eruption of mount pinatubo causing global temperatures to drop by 1c

what hazards are created at a collision zone (convergent destructive) boundary

the collision causes land to squeeze upwards and fold mountains to form such as the himalayas as the ground buckles and reshapes under pressure. severe earthquakes can occur in the process

what hazards are created at a constructive (divergent) boundary

as plates move apart magma from the mantle can reach the surface and erupt through fissures and faults causing volcanoes and creating new land as lava emerges and spreads out such as in the eyjafjallajokull eruption in 2010

what hazards are created at a conservative plate boundary

as the plates move past each other their rough edges snag and stick like velcro causing friction and stress to build up until they jolt forwards causing violent earthquakes and some rifts in the land such as in the lake kiva earthquake in 2008

what is the crust like

oceanic crust is 5-10km thick such as the pacific plate and the continental crust is 25-100km thick such as the north American plate

what is the mantle like

starts underneath the crust and continues 3000km below the earth’s surface and it behaves like a solid but flows slowly with temperatures that can reach 4000c

what is the outer core like

depth starts 2890km and extends down to 5270km and it is a liquid with temperatures ranging between 4030 and 5730c

what is the inner core like

depth starts at 5270km and continues down to 6354km and is made of solid nickel and iron as they are magnetic metals

what is continental drift

the process of tectonic plates moving over time causing the changing relative positions of continents

what is the theory of plate tectonics

the outer layer of the earth is split up into plates which all move in different directions

explain convection currents

convection currents cause tectonic plates to move and radioactive decay in the core causes plumes of magma in the mantle to rise because they are hot so less dense and lighter than the material around it. when it reaches the crust it can no longer rise because the magma below it is still rising meaning it splits apart and slowly pulls the crust apart with it. as they go further apart they cool down and sink down again and overall these are called convection currents and the cycle repeats

what is an earthquake

a violent shaking of the earth’s crust

what causes an earthquake

tectonic plates are not smooth but jagged and rocky so when they move past each other they grind together and snag/stick which causes stress and friction between the plates so pressure and potential energy build up and the rock at the stress point beneath the surface starts to deform. eventually when the energy reaches a certain point the rocks will suddenly move or slip and break at the focus point causing the plates to jolt forwards which is the start of an earthquake. this sudden movement releases energy through seismic waves which radiate from the focus to the surface shaking the crust and moving the plates again causing an earthquake

what is the focus

the point where the earthquake starts

what is the epicentre

it is a point directly above the focus point above the surface

what are seismic waves

they are waves of energy released from the focus of an earthquake. p waves are fast but cause not much damage whereas s waves are not fast but cause lots of damage

what are primary effects and give examples for earthquakes

occur instantly and as a direct result of the hazard such as the ground shaking and buildings collapsing

what are secondary effects and give examples for earthquakes

consequences of something else happening such as people being injured from falling debris from the collapsed buildings and tsunamis and landslides and avalanches

what factors impact the amount of damage

time population density size of area enough warning preparation and aftermath

what is the Richter scale

measures the power of the shaking based on measurements from a seismometer and the scale is logarithmic so every time you go up one on the scale there is 10x amplitude and 30x energy

what is the Mercalli scale

measures the intensity of the impacts of the earthquake so the damage

evaluate the usefulness of the Richter scale and the Mercalli scales in measuring the impact of earthquakes

the richter scale is useful because it measures the power if the actual shaking so the amount of energy and amplitude. this is useful because it shows the size of the earthquake and bigger earthquakes with more shaking cause more damage and things breaking so the bigger the impact will be. the mercalli scale measures the amount of damage an earthquake causes is useful because it shows how the earthquake impacted the civilians around it and therefore what the infrastructure and preparedness of the city was like. overall the richter scale is more useful because it is objective so everyone will get the same answer unlike the mercalli scale which is subjective so everyone’s view would be different so therefore the richter scale is more reliable

composite volcanoes (aka stratovolcanoes)

found at destructive plate boundaries where the plates are moving towards each other and the magma there is viscous and sticky so moves more slowly and can lead to more explosive eruptions. steeper sided volcanoes are built up in layers every time an eruption occurs a bit like layers on a cake and most of these volcanoes are found along the infamous ring of fire around the pacific ocean in places such as indonesia. often have andesitic lava

sheild volcanoes

found at constructive plate boundaries where the plates moving away from each other allowing hot magma from the mantle to flow up by convection and be erupted to the surface. often the magma erupted is more fluid and spreads out from the cone or through fissures and this builds a gentle volcano shape. you can see these in places like iceland where new oceanic plate is being formed and often have basaltic lava

fissure volcano

found at constructive plate boundaries when the plates separate to leave a rift or a fissure. the eruption does not form a cone but lava flows out along a fault line and builds up for example in iceland or at the mid atlantic ridge

Caldera volcano

occurs when a volcano erupts so explosively that the magma chamber empties and the caldera collapses on itself so eventually magma rises again and and a new cone will grown. calderas can be over 1 mile in diameter for example yellowstone in the USA

what is a volcano

an opening in the earth’s crust through which lava ash and gases are erupted from the mantle

what are lahars

volcanic mudflow

what are lava bombs

bombs of ejected lava that explode as liquid rock

what are pyroclastic flows

mixture of hot gas over 800c and tephra which are rock fragments ejected from the volcano

what are ash clouds

combination of volcanic ash and debris

what are sulphur deposits

solid sulphur rock ejected

what is geothermal power

power generated by water heated up underground by volcanic activity

what are lava flows

outrun that will destroy anything it touches

what are Jokulhlaups

glacial meltwater

what are types of fluid lava and where is it found

basaltic found on constructive plate margins

what are types of viscous lava and where is it found

andesitic and rhyolitic found on destructive plate margins

how does the lava viscosity effect eruptions

for more fluid lava the sulphur dioxide which was trapped can escape more easily and the eruptions will be less vigorous and more often however for more viscous lava the sulphur dioxide cannot escape as easily meaning pressure builds up and the eventual eruptions are more vigorous but less often

explain how composite volcanoes are formed on a destructive plate boundary

due to convection currents in the mantle the oceanic and continental plates move towards each other and at the destructive plate boundary where they meet the oceanic plate is more dense than the continental plate so when it subducts it is forced into the mantle where it melts and becomes magma due to the high temperatures and this magma rises under pressure and erupts as a composite volcano

how do you measure the severity of volcanic eruptions

the volcanic explosivity index VEI which runs between 0 and 8 and takes into account how far the ash plume travelled and the volume of material ejected and how often the eruption happened

explain how hotspot volcanoes happen

a stationary plume of magma in the mantle rises up and creates a fissure in the crust causing magma to rise up and erupt to the surface causing a volcano. as the oceanic plate moves the volcano is no longer over the stationary plume of magma so becomes extinct and is weakened and eroded. meanwhile new active volcanoes are created where the plume of magma is and over time a line of volcanoes is created. usually on oceanic plates

where is Eyjafjallajokull

on the south coast of iceland around 150km away from reykjavik

what are the causes of the E-15 eruption

the north american and eurasian plate move apart on a constructive plate boundary causing fissures in the E-15 composite volcano. lava erupted out of those fissures leaving space for more viscous magma from deeper down to rise up causing a second eription on the 15th of april 2010 which was more explosive. normally eruptions on constructive plate boundaries are not very explosive but because the basaltic lava mixed with viscous lava it was more explosive

what is a primary effect of E-15 on an international scale

there was 250 million cubic meters of ash in the air so 95000 flights were cancelled over a two week period which caused problems on an international scale because lots of airlines around the world could not fly as they were worried their engines would break if ash was drawn into them when they were flying and they would have to be rebuilt. however the flights being cancelled caused airlines to lose a lot of money £2billion in total

what is a secondary effect of E-15 on a local scale

local water supplies became contaminated with fluoride which caused problems on a local scale because farmers could not get all their sheep inside before they drank the water as the sheep were spread out over a large area and there was hardly any visibility. this meant some sheep drank the water with fluoride in it and died however only a small number died because the fluoride was only more concentrated near the volcano

what is a secondary effect of E-15 on a national scale

flooding due to the glacial meltwater which destroyed route 1 which caused problems on a national scale because route 1 is a very important road in iceland so it being destroyed made travelling around the country much more difficult as route 1 connected most places so there was more traffic on other roads and increased commute and travel times without it

what were the responses to the E-15 eruption

icelandic meteorological office IMO used 80 seismometers and 120 GPS antennas to find out any problems with volcanoes and then send alerts to the public telling them to be aware of the risks and take precautions such as wearing goggles. iceland also have a well trained national emergency agency who made pre built structures to dredge blocked rivers and clear away tonnes of ash

what is mitigation and what are the three methods

the act of reducing the impact or risk of a hazard by prediction preparation and protection

what will effect the impact of a tectonic hazard

distance from epicentre as it will have a bigger effect if it is shallower and magnitude and duration of the earthquake and building design and preparedness of the population so if they have advanced warnings and organised relief in place and geology

what are methods of predicting earthquakes

passing electromagnetic shocks or waves through rocks might detect fractures beginning to develop before an earthquake and looking at historic trends to help identify timescale patterns however this is not very useful for predicting earthquakes because although they could tell us roughly when the earthquake might be they do not tell us where

what are methods of predicting volcanoes

satellite imagery as thermal scanning can show if magma is rising up and seismometers can be used because they show where earthquakes are so if you use three or more you can use trigonometry to predict where a magma chamber is rising which build up pressure and results in an eruption making them useful

what is a method of protection against earthquakes

making buildings earthquake resistant so it does not collapse on people trying to get out during an earthquake by putting dampers at the top of buildings to balance them out and make them sway less and using steel to reinforce concrete in buildings as it is flexible and base isolation to dissipate shock waves from earthquakes

what is are methods of protection against volcanoes

buildings can be insulated and barriers put in place to reduce ash entry and gas masks made available. also in Heimaey in Iceland they have a fissure volcano because the north american and eurasian plates are moving apart however the E-15 eruption caused lava to slowly flow towards the ports in Heimaey and as it is a fishing town they protected their ports by using water from the sea to solidify the lava at the front so the still fluid lava behind it would be blocked from reaching the ports and would have to be redirected so take a different route

assess the methods of preparation for earthquakes

in Japan they have earthquake awareness day on the 1st of september where evacuations are practiced and people are educated on what to do in an earthquake and also in Taiwan the skyscraper taipei 101 uses a heavy weight damper at the top of the building so when the building moves one way the damper moves the other and reduces how much it sways. the awareness day is better because it helps the whole of japan reduce the impacts of an earthquake but the damper only helps one building

assess the methods of preparation for volcanoes

the IMO provides warnings to people via text messages tv and radio so people can take safety precautions or focus on a safe evacuation and also scientists can make accurate predictions of volcanic eruptions using seismometers and measuring gas emissions as concentrations of sulfur dioxide increase as the magma rises. the scientist predictions are better because you need to know if and when the volcano is going to erupt before you can send out alerts and prepare the country

how do you know if an exam question is asking about earthquakes or volcanoes

seismic means just earthquakes but tectonic means earthquakes ad volcanoes

what is easier to predict earthquakes or volcanoes and why

volcanoes are easier to predict as they are obvious visible places on the earths surface so lots of measuring equipment can be put there to detect if they are going to erupt soon whereas earthquakes could happen anywhere on a plate margin so are harder to predict