Topic 1- Hazardous Earth

Question 1

Explain how winds transfer heat from the equator to the poles

Answer 1

.The sun heats the earth’s surface unevenly and the isolation (the solar radiation that reaches the earth’s surface) is greater at the equator than the poles

.The differences in temperature cause differences in air pressure. Winds blow from areas of high pressure to the areas of low pressure transferring heat away from the equator

.Winds are part of global atmospheric circulation loops called cells. These loops have warm rising air which creates a low pressure belt and cool failing air which creates a high pressure belt

.There are three cells in each hemisphere- the Hadley, Ferrel and Polar cells

Question 2

Explain how global atmospheric circulation works

Answer 2

1) At the equator the sun warms the earth which transfers heat to the air above causing it to rise. This creates a low pressure belt. As the air rises, it cools and condenses forming clouds and rain.
2) The cool, dry air moves out to 30 degrees north and south of the equator.
3) At 30 degrees north and south of the equator, the cool air sinks creating a high pressure belt with cloudless skies and very little rainfall.

4) The cool air reaches the ground surface and moves as surface winds either back to the equator or towards the poles:
. Surface winds blowing towards the Equator are called Tradewinds
.Trade winds blow from the SE in the southern hemisphere and the NE in the northern hemisphere. At the equator these trade winds meet and are heated up by the sun which causes them to rise and form clouds
.Surface winds blowing towards the poles are called westerlies. They blow from the NW in the Northern hemisphere and from the SW in the Southern hemisphere.

5) At 60 degrees north and south of the equator, the warmer surface winds meet colder air from the poles. The warmer air is less dense than the cold air so it is forced to rise creating low pressure and frontal rain(rain that forms where the warm and cold air masses meet).
6) Some of the air moves back towards the equator and the rest moves towards the poles.
7) At the poles the cool air sinks creating high pressure. The high pressure air is drawn back towards the equator as surface winds.

Question 3

What are the three cells in each hemisphere called?

Answer 3

.The Hadley, Ferrel and Polar cells

Question 4

How is heat transferred by ocean currents?

Answer 4

.Ocean currents are large scale movements of water that transfer heat from warmer to cooler regions.

.Surface currents are caused by winds and help to transfer heat away from the equator (e.g the Gulf Stream brings warm water from the Caribbean and keeps Western Europe warmer than it would otherwise be)

. There are also deep ocean currents driven by differences in water density. When water freezes at the poles, the surrounding water becomes saltier, increasing its density. As it gets denser, it sinks, causing warmer water to flow in at the surface creating a current. This warmer water is cooled and sinks, continuing the cycle. This cycle of cooling and sinking moves water in a big loop round the Earth which is known as thermohaline circulation

Question 5

What are the different climate zones around the world?

Answer 5

. The pressure belts caused global atmospheric circulation cause variations in climate

.Arid(dry): Sinking air from the Hadley and Ferrel cells meeting causes high pressure and prevents rainfall. Rainfall is very low for all or most of the year. Temperatures are hot or warm.

.Polar: Sinking air from the Polar cells creates an area of high pressure at the poles. Temperatures are low all year round and there’s very little rainfall

.Tropical: Rising air from the two Hadley cells meeting causes low pressure and lots of rainfall. Temperatures are hot all the time and rainfall is high.

Question 6

Explain how the earth’s climate is always changing and what is climate change?

Answer 6

.Climate change is any significant change in the Earth’s climate over a long period. The climate constantly changes.

.The Quaternary period is the most recent geological time period spanning from about 2.6 million years ago to present day

.In the period before the quaternary, the Earth’s climate was warmer and quite stable. Then things changed a lot.

.During the quaternary, global temperature has shifted between cold glacial periods that last for around 100,00 years and warmer interglacial periods that usually last for around 10,000 years

.The last glacial period ended around 15,000 years ago. Since then the climate has been warming

Question 7

Explain how orbital changes are a natural cause of climate change

Answer 7

.Orbital changes are variations in the way the Earth moves around the sun

.Stretch(also called eccentricity): the path of the Earth’s orbit around the sun changes from an almost perfect circle to an ellipse(an oval) and back again every 96,000 years

.Tilt: the Earth’s axis is tilted at an angle as it orbits the sun. This tilt changes over a cycle of about 41,000 years

.Wobble(also called precession): the axis of the Earth wobbles like a spinning top on a cycle of about 22,000 years

.These cycles affect the amount of solar radiation (energy) the earth receives. If the earth receives more energy, it gets warmer

.Orbital changes may have caused the glacial and interglacial cycles of the quaternary period

Question 8

Explain how volcanic activity is a natural cause of climate change

Answer 8

.Major volcanic eruptions eject large quantities of material e.g. ash into the atmosphere

.Some of these particles reflect the Sun’s rays back out to space so the earth’s surface cools

.Volcanic activity may cause short term changes in the climate, e.g. the eruption of Mount Tambora in Indonesia in 1815 lead to the ‘year without a summer’ in 1816

Question 9

Explain how solar output is a natural cause of climate change

Answer 9

.The Sun’s output of energy isn’t constant as it changes in short cycles of about 11 years and possibly also in longer cycles of several hundred years

.Periods when solar output is reduced may cause the Earth’s climate to become cooler

.The Maunder Minimum was a period of reduced solar activity between 1645 and 1715 which coincided with the Little Ice Age

Question 10

Explain how asteroid collisions are a natural cause of climate change

Answer 10

. Asteroids hitting the Earth’s surface can throw up huge amounts of dust into the atmosphere

.These particles prevent the Sun’s energy from reaching the Earth’s surface so global temperatures fall(possibly for several years)

.Some scientists believe that an asteroid collision caused a period of global cooling around 12,000 years ago

Question 11

How are tree rings evidence for natural climate change?

Answer 11

. Most rings produce one ring within their trunk every year

.The thickness of the ring depends on the climate when the ring was formed, when it’s warmer the rings are thicker

.Scientists take cores through tree trunks then date each ring by counting them back from when the core was taken. By looking at the thickness of the rings, they can see what the climate was like each year

Question 12

How are ice cores evidence for natural climate change?

Answer 12

. Ice sheets are made up of layers of ice as one layer is formed each year

.Scientists drill into ice sheets to get long cores of ice

.By analysing the gases trapped inside the layers of ice they can tell wha the temperature was each year

.One ice core(the vostok ice core) from the Antarctica shows the temperature change over the past 400,000 years

Question 13

How are historical records evidence for natural climate change?

Answer 13

.Since the 1850s global temperature have been accurately measured using thermometers. This gives a reliable but short-term record of climate change

. Historical records(e.g. diaries and paintings) can extend the record of climate change a bit further back. For example, historical diaries can show what climate change was like in the past, e.g. by giving the number of days of rain or snow and the dates of harvests

.Paintings of fairs and markets on frozen rivers show that winters in Europe were regularly much colder 500 years ago then they are now

Question 14

Explain the medieval warm period

Answer 14

. The medieval warm period was a period of warming between 900 and 1300

.Harvest records show that England was warm enough to grow large amounts of grapes

.Tree ring data suggests this was also the case during Roman times were temperatures were 1 degrees warmer than today

Question 15

Explain the little ice age

Answer 15

.The little ice age was a period of cooling that followed the medieval warm period

.Paintings from the 17th century shows the London frost fairs which took place on the frozen River Thames

.Historical records talk about arctic ice reaching as far south as scotland and sightings of insuits

Question 16

Explain how the natural greenhouse effect is essential for keeping our planet warm

Answer 16

1) The temperature of the earth is a balance between the heat it gets from the Sun and the heat it looses to space
2) The incoming energy from the sun is short-wave radiation. The outgoing energy from the Earth is long-wave radiation
3) Gases in the atmosphere naturally act like an insulating layer- they let short-wave radiation in, but trap long-wave radiation, helping to keep the Earth at the right temperature
4) This is called the greenhouse effect
5) Gases that trap heat are called greenhouse gases- they include carbon dioxide and methane
6) Some greenhouse gases are stronger than others,e.g. methane absorbs more heat than carbon dioxide
7) Different greenhouse gases stay in the atmosphere for different lengths of time. For example, methane usually stays in the atmosphere for 10 years after being emitted
8) The longer the gases stay in the atmosphere, the more they’ll contribute to warming

Question 17

Explain how human activities are making the greenhouse effect stronger

Answer 17

.The rate of the recent rise in global temperature is unheard of

.There’s a scientific consensus(general agreement) that human activities are causing global warming by making the greenhouse effect stronger. This is called the enhanced greenhouse effect

.Too much greenhouse gas in the atmosphere means too much energy is trapped and the planet warms up

.Humans are increasing the concentration of greenhouse gases

Question 18

Explain how farming increases the concentration of greenhouse gases

Answer 18

.Farming of livestock produces a lot of methane( cows fart)

.Rice paddies contribute to global warming, because flooded fields emit methane

.Trees absorb and store co2. When land is cleared of trees for agriculture it stops the absorption of co2, which leaves more co2 in the atmosphere

Question 19

Explain how industry increases the concentration of greenhouse gases

Answer 19

.Most industry uses a lot of energy

.Some industrial processes also release greenhouse gases,e.g. cement is made from limestone, which contains carbon. When cement is produced, lots of co2 is released into the atmosphere

.Industrial waste may end up in landfill sites where it decays, releasing methane

Question 20

Explain how energy increases the concentration of greenhouse gases

Answer 20

.co2 is released into the atmosphere when fossil fuels like coal, oil and natural gases are burnt,e.g. in power stations

Question 21

Explain how transport increases the concentration of greenhouse gases

Answer 21

.Most cars,lorries,ships and planes run on fossil fuels, which release greenhouse gases when burnt

.Car ownership is rapidly increasing in countries that are developing,e.g. china

.This means there are more cars on the roads especially in urban areas

.This increases congestion. As a result, car engines are running for longer, so the amount of greenhouse gases released increases

Question 22

How is declining arctic ice evidence for human activity causing climate change?

Answer 22

.Sea ice forms around the poles in winter when ocean temperatures fall below -1.9 degrees and melts during the summer when its warmer

.The extent of arctic sea ice in winter has decreased by more than 3% each decade over the past 35 years

Question 23

How is sea level rise and warming oceans evidence for human activity causing climate change?

Answer 23

.Since 1901 sea levels have risen by almost 0.2m. Scientists have highlighted two factors behind the rise

1) Eustatic sea rise- warmer temperatures are causing glaciers to shrink and ice sheets to melt. The melting of ice on land, especially from the Greenland and Antarctic ice sheets, means that water stored on land as ice returns to the oceans. This causes sea levels to rise
2) Thermal expansion- water in the oceans expands as it gets warmer which is called thermal expansion. Scientists think this accounts for about half of the measured rise in sea levels

Question 24

How is global temperature rise evidence for human activity causing climate change?

Answer 24

.Temperatures have increased by nearly 1 degree since 1880 and are expected to rise by 0.3-4.8 degrees between 2005 and 2100. The top ten warmest years since records began have all been since the year 2000

Question 25

How are extreme weather events evidence for human activity causing climate change?

Answer 25

.Since 1950 there has been a higher frequency of heat waves in many areas and fewer cold weather events

.In the UK, more rainfall records were broken in 2010-2014 than in any other decade on record, even after only half a decade. 2013 was one of the wettest years on record and December 2015 was the wettest month ever recorded in the UK

Question 26

Explain what serious impacts climate change can have on people

Answer 26

.In some places deaths due to death have increased but deaths due to cold have decreased

.Some areas could become so hot and dry that they’re difficult or impossible to inhabit. Low-lying coastal areas could be lost to the sea or flood so often that they are also impossible to inhabit. This could lead to migration and overcrowding in other areas

.Farming is being affected by climate change. Globally some crops have suffered from climate change but some farmers in high-latitude countries which are countries further away from the equator are finding that crops benefit from warmer conditions

.Lower crop yields could lead to malnutrition,ill health and death from starvation particularly in lower latitudes which are away from the equator

.Climate change means the weather is getting more extreme. This means that more money has to be spent on predicting extreme weather events, reducing their impacts and rebuilding after them

Question 27

Explain how data about climate change can be used to make predictions

Answer 27

.Physical processes can be modelled on computers such as atmospheric circulation and volcanic eruptions

.Human activity such as growth of industry can also be modelled using data that has been collected about greenhouse gas emissions

.Scientists can use these models to work out how the climate would be affected under certain scenarios such as what would happen if there was a volcanic eruption in 20 years time and there were still high levels of greenhouse gas emissions

. The Intergovernmental Panel on Climate Change (IPPC) is an international group of scientists that uses models to predict how the climate may change and the consequences

.The IPPC have chosen four “Representative Concentration Pathways” which are possible scenarios covering the best and worst possible outcomes. The IPPC use projection graphs to show the predicted changes in temperature and sea level rise by 2100.Lines for the best and worst scenarios are plotted on graphs. All other outcomes fall in between the lines

.Scenario 1: Minimum emissions- The best outcome in which levels of greenhouse gases peak and then reduce

.Scenarios 2 and 3: Stabilising scenarios- Where gas levels continue to increase but eventually level off after steps are taken to reduce emmisons

.Scenario 4: Maximum emissions- Worst outcome in which the rate of production of emissions continues to increase and greenhouse gases end up very high

Question 28

Explain how there is a lot of uncertainty about future climate change

Answer 28

.Emissions- we don’t know how emissions will change. Predictions have to take into account factors such as population increase and economic development. It’s hard to know how global population will change in the future or how much development will take place

.Complexity-we don’t know what exact climate changes each scenario will cause. There are lots of natural processes we don’t understand which makes it difficult to predict what will change. We don’t know what the effect these natural processes will have on the environment

.Management- we don’t know what attempts there will be to manage the amount of greenhouse gases in the atmosphere and how successful they’ll be

Question 29

Explain the formation of a tropical cyclone

Answer 29

1) Tropical cyclones develop when the sea temperature is 26.5 degrees or higher and when the wind shear(difference in wind speed) between higher and lower parts of the atmosphere is low
2) The source area of most tropical cyclones is between 5 degrees and 30 degrees north and south of the equator as any further away from the equator and the water isn’t warm enough
3) The majority of cyclones occur when sea temperatures are highest- in the northern hemisphere this is June to November. In the southern hemisphere this is November to April
4) Warm,moist air rises and condensation occurs. This releases huge amounts of energy, which makes the storms powerful. The rising air creates an area of low pressure which increases surface winds
5) The Earth’s rotation deflects the path of winds, which causes the cyclone to spin
6) Tropical cyclones move towards the west because of the easterly winds near the equator
7) When cyclones travel further away from the equator, their path may start to curve to the east as they get caught in the mid-latitude westerlies
8) Cyclones intensify (get stronger) due to energy from the warm water
9) They diessapitate (lose strength) when they move over land or cooler water because the energy supply from the warm water is cut off. Changes in windspeed, from meeting other weather systems, can also cause a cyclone to diessapitate
10) Climate change may cause tropical cyclone source areas to change. If sea temperatures rise, more of the world’s oceans could be above 26.5 degrees which means more places in the world may experience tropical cyclones

Question 30

List the features and structure of a tropical cyclone

Answer 30

.Tropical cyclones are circular in shape, hundreds of kilometres wide and often last 7-14 days

.Eye: The centre of the cyclone is called the eye- it’s up to 50km across and is caused by descending air. There’s very low pressure,light,winds,no clouds, no rain and a high temperature in the eye

.Eye-wall: The eye is surrounded by the eyewall, where there’s spiralling rising air, very strong winds(around 160 km per hour), storm clouds,torrential rain and a low temperature

.Edges: Towards the edges of the cyclone the wind speed falls, the clouds become smaller and more scattered, the rain becomes less intense and the temperature increases

.Tropical cyclones spin anticlockwise in the Northern hemisphere and clockwise in the southern hemisphere

Question 31

What are some of the physical hazards of tropical cyclones?

Answer 31

.High winds-wind speeds in a tropical cyclone can reach 250km/h

.Intense rainfall-tropical cyclones can release trillions of litres of water per day as rain.The rain gets heavier as you get closer to the eye of the cyclone

.Storm surges-a storm surge is a large rise in sea level caused by low pressure and high winds

.Coastal flooding-flooding happens as a result of storm surges and strong winds driving large waves onto the shore

.Landslides-heavy rain makes hills unstable,causing landslides

Question 32

Explain how physical hazards of tropical cyclones have an impact on people

Answer 32

.People may drown in the strong currents created by floodwater and storm surges

.Windspeeds in tropical cyclones can be strong enough to completely destroy buildings leaving people homeless

.High winds and flood water can carry large amounts of debris, which can kill or injure people

.Electricity supplies are cut off because cables are damaged or swept away by floodwater

.Flooding causes sewage overflows which contaminate water supplies

.The shortage of clean water and lack of proper sanitation makes it easy for disease to spread

.In poorer countries, there’s often a shortage of food because crops are damaged and livestock are killed

.Unemployment increases because businesses are damaged or destroyed

.Damaged roads make it very difficult for aid and emergency vehicles to get through

Question 33

Explain how physical hazards of tropical cyclones have an impact on the enviroment

Answer 33

.Trees are uprooted by high winds which can damage or completely destory wooded habitats

.Storm surges can erode beaches and damage coastal habitats

.Flooding caused by storm surges can pollute freshwater environments with salt water

.Landslides deposit sediment in rivers and lakes which can kill fish and other wildlife

.Flooding can cause damage to industrial buildings on the coast,e.g. coal or oil factories. This causes harmful chemicals to leak into the environment and cause pollution

Question 34

How are some countries more vulnerable to tropical cyclones than others

Answer 34

.Physical vulnerability: low lying coastlines are vulnerable to storm surge flooding as well as large waves caused by high winds. Areas in the path of tropical cyclones are hit more frequently. Steep hillsides may increase the risk of landslides

.Economic vulnerability: poorer countries are economically vulnerable. Many people depend on agriculture which is often badly affected and leads to the loss of livelihoods. People may not have insurance to cover the cost of repairing damage caused by cyclones. However, the economic impact is often greater in countries that are richer because the buildings and infrastructure damaged are worth a lot more money (e.g. roads,bridges and rail)

.Social vulnerability: poorer countries are often more socially vulnerable. Buildings are poorer quality so more easily damaged. Healthcare isn’t as good so they struggle to treat all the casualties. There is little money for flood defences or training emergency teams. It is harder to rescue people because of poor infrastructure

Question 35

List some of the strategies to prepare for and respond to tropical cyclones

Answer 35

.Forecasting: when and where tropical cyclones will hit land can be predicted. Scientists can use weather forecasting and satellite technology to monitor cyclones. Computer models are then used to calculate a predicted path for the cyclone. The cyclone’s magnitude can be monitored by measuring its wind speeds. Predicting where and when a tropical cyclone is going to happen gives people time to evacuate and protect their homes and businesses, e.g. by boarding up windows

.Evacuation: warning strategies are used to alert people to a tropical cyclone. An alert will give people enough time to leave their homes and get to a save place. Governments can plan evacuation routes to get people away from storms quickly. In Florida, evacuation routes are signposted all along the coast. Successful evacuations can reduce the number of deaths and injuries. Emergency services can train and prepare for disasters,e.g. by practising rescuing people from flooded areas with helicopters. This reduces the number of people killed

.Defences: defences such as sea walls can be built along the coast to prevent damage from storm surges. Buildings can also be designed to withstand a storm surge, e.g. they can be put on stilts so they’re safe from the floodwater. This will reduce the number of buildings destroyed, so fewer people will be killed, injured, made homeless and made unemployed

Question 36

Give an example of a tropical cyclone in a developed country and in a developing country

Answer 36

Tropical cyclone in a developed country: Hurricane Katrina,category 3 at landfall,South east USA,29th August 2005

Tropical cyclone in a developing country: Cyclone Nargis,Category 4 at landfall, Irrawaddy delta Myanmar,2nd may 2008

Question 37

Explain the features of Hurricane Katrina

Answer 37

.Forecasting: the USA had a sophisticated monitoring system to predict if and where a hurricane will hit. The National Hurricane Centre in Florida tracks and predicts hurricanes using satellite images and planes that collect weather data upon approaching storms

.Warning and Evacuation: the NHC issued a hurricane warning on the 26th August for Louisiana,Mississippi and Alabama. It continued to track the hurricane updating the government on where and when it would hit. Mississippi and Louisiana declared states of emergency and 70%-80% of New Orleans residents were evacuated before the hurricane reached land. This reduced the number of people killed because lots of people had left the areas where the hurricane hit

.Defences: The city of New Orleans was very badly damaged – flood defences (e.g.embankments) that were supposed to protect the city failed. This caused widespread flooding (over 80% of the city was underwater)

.Impacts on the environment: coastal habitats such as sea turtle breeding beaches were damaged. Some coastal conservation areas were destroyed, e.g. around half of Breton National wildlife refuge in Louisiana was washed away. Flooding damaged oil refineries in Louisiana, causing massive oil spills

Impacts on people: more than 1800 people were killed. 300,000 houses were destroyed and hundreds of people were made homeless. 3 million people were left without electricity. Roads were damaged and some bridges collapsed. 230,000 jobs were lost from damaged businesses

Question 38

Explain the features of cyclone Nargis

Answer 38

.Forecasting: Myanmar doesn’t have a dedicated monitoring centre for tropical cyclones. Myanmar doesn’t have a radar network that can predict the height of storm surges and waves caused by cyclones

.Warning and evacuation: Indian weather agencies warned the government of Myanmar that hurricane Nargis was going to hit the country 48 hours before it did.Warnings were issued on the TV and radio but they didn’t reach the poor rural communities. This meant more people were killed because they didn’t know what to do or where to evacuate to. There were no emergency preparation plans,no evacuation plans and the country didn’t have an early warning system

.Defences: Mangrove forests protected the coast from flooding but loads had been chopped down in the decade before Nargis hit, reducing the natural protection

.Impacts on the environment: the Irrawaddy delta in Myanmar was the hardest hit area and a large proportion of it is only just above sea level and 14000km2 of land was flooded. 38000 hectares of mangrove forests were destroyed.The flooding caused erosion and salination(increased salt content) of the land

.Impacts on people: more than 140,000 people were killed. 450,000 houses were destroyed, 350,000 were damaged. Around 65% of rice paddies in the Irrawaddy delta were damaged, which lead to a loss of livelihoods. A lot of people suffer from diseases caused by poor sanitary conditions and contaminated water

Question 39

Explain the structure of the earth

Answer 39

Inner core,outer core,mantle and crust

.At the centre of the earth is the core: the core is a ball of solid(inner) and liquid(outer) iron and nickel. At the centre, its very dense. It becomes less dense further out. The temperature inside the core ranges from 4400-6000 degrees

.Around the core is the mantle: the mantle is made up of silicon-based rocks. The part of the mantle nearest to the core is quite rigid. The layer above this, called the asthenosphere is semi-molten and it can flow. And the very top bit of the mantle is rigid. The temperature of the mantle is between 1100 and 3700 degrees. It’s hotter towards the core and colder towards the Earth’s surface

.The solid outer layer of the Earth is called the crust: the crust is also made up of silicon based rocks. There are two types of crust, oceanic which is thinner and more dense and continental which is thicker and less dense. The crust is divided into slabs called tectonic plates

Question 40

How do tectonic plates move due to convection currents in the mantle?

Answer 40

1) The tectonic plates float on the mantle
2) Radioactive decay of some elements in the mantle and core,e.g. uranium generates a lot of heat
3) when lower parts of the asthenosphere heat up they become less dense and slowly rise
4) As they move towards the top of the asthenosphere they cool down, become more dense, then slowly sink.
5) The circular movements of semi-molten rock are called convection currents
6) Convection currents in the asthenosphere create drag on the base of the tectonic plates (which are solid and rigid) and this causes them to move

Question 41

What are convection currents?

Answer 41

.Convection currents in the mantle move tectonic plates in different directions

. Plate boundaries are where the plates meet

. The movement of the plates crates three types of boundaries

.Convergent boundaries, divergent boundaries, Conservative boundaries

Question 42

What is a Convergent Boundary?

Answer 42

. Convergent boundaries are where two plates are moving towards each other,e.g. along the west coast of South America

. When an oceanic plate meets a continental plate, the denser oceanic plate is forced down into the mantle and destroyed.This often crates volcanoes and ocean trenches

. When two continental plates meet the plates collide and the ground is folded and forced upwards to create mountain ranges

Question 43

What is a Divergent Boundary?

Answer 43

. Divergent boundaries are were two plates are moving away from each other, e.g. at the mid-Atlantic Ridge. Magma (molten rock) rises from the mantle to fill the gap and cools, creating new crust

Question 44

What is a Conservative Boundary?

Answer 44

. Conservative boundaries are where two plates are moving sideways past each other, or are moving in the same direction but at different speeds,e.g. along the west coast of the USA. Crust isn’t created or destroyed

Question 45

Where are volcanoes found?

Answer 45

.At convergent plate boundaries the oceanic plate goes underneath the continental plate because it’s more dense. The oceanic plate moves into the mantle, where it’s melted and destroyed. A pool of the magma forms. The magma rises through cracks in the crust called vents.The magma eruputs onto the surface (where it’s called lava) forming a volcano

.At divergent boundaries the magma rises up into the gap created by the plates moving apart, forming a volcano

. When a volcano erupts, it emits lava and gases. Some volcanoes emit lots of ash, which covers land, blocks out the sun and forms pyroclastic flows which are superheated currents of gas,ash and rock

Question 46

What are hotspots?

Answer 46

.Some volcanoes form in the middle of tectonic plates over hotspots

.They occur when a plume of hot magma from the mantle moves towards the surface, causing an unusually large flow of heat from the mantle to the crust

.Sometimes the magma can break through the crust and reach the surface. When this happens, there’s an eruption and a volcano forms

.Hotspots remain stationary over time, but the crust moves above them. This can create chains of volcanic islands,e.g. Hawaii is a chain of volcanic islands in the middle of the Pacific plate

Question 47

What are the different types of volcanoe?

Answer 47

1) Composite volcanoes(e.g. Mount Fuji in Japan)
.Occur at convergent plate boundaries
. Subducted oceanic crust contains lots of water. The water reacts with magma and creates gases, which cause the subducted crust erupt
.They have explosive eruptions that start with ashy explosions that deposit a layer of ash
.They erupt andesitic lava that has a high silica content which makes it thick and sticky.The lava can’t flow far so forms a steep sided cone

2) Shield volcanoes(e.g. Mauna Loa in the Hawaiian islands)
.Occur at hotspots or divergent plate boundaries
.They are not very explosive and only contain lava
.They erupt basaltic lava, which has a low silica content and is runny. It flows quickly and spreads over a wide area forming a low,gentle-sided volcano

Question 48

How do earthquakes occur at all three types of plate boundary?

Answer 48

1) earthquakes are caused by tension that builds up at all three types of plate boundary:
. Convergent boundaries – tension builds up when one plate get stuck as it’s moving down past the other into the mantle
. Divergent boundaries – tension builds along cracks within the plates as they move away from each other
.Conservative boundaries-tension builds up when plates that are grinding past each other get stuck

2) The plates eventually jerk past each other, sending out shockwaves (vibrations). These vibrations are the earthquake
3) Earthquakes are measured using the moment magnitude scale, which measures the energy released by an earthquake.You may still see some references to the Richter scale but it’s no longer used by scientists

Question 49

How do earthquakes occur at various depths?

Answer 49

1) The focus of an earthquake is the point in the Earth where the earthquake starts. This can be at the earths surface, or anywhere up to 700 km below the surface
2) shallow – focus earthquakes are caused by tectonic plates moving at or near the surface. They have a focus between 0 km and 70 km below the Earth surface
3) deep – focus earthquakes are caused by crust that has previously been subducted into the mantle (e.g. at convergent plate boundaries)moving towards the centre of the Earth,heating up or decomposing. They have a focus between 70km and 700km below the Earth’s surface
4) In general, deeper earthquakes do less damage at the surface than shallow earthquakes. Shock waves from deeper earthquakes have to travel through more rock to reach the surface,which reduces their power when they reach the surface

Question 50

How can earthquakes cause tsunamis?

Answer 50

.Tsunamis are a series of enormous waves caused when huge amounts of water are displaced

.Underwater earthquakes can cause the seabed to move, which displaces water. Waves spread out from the epicentre of the earthquake which is the point of the earth’s surface that’s straight above the focus

.The depth of an earthquake affects the size of the tsunami-shallow focus earthquakes displace more water as they’re closer to the Earth’s surface. This increases the size of the tsunami

.The waves travel very fast in deep water so they can hit the shore without much warning. Thus causing a high death toll

Question 51

What are the methods for predicting tectonic hazards for earthquakes?

Answer 51

1) Earthquakes cannot be reliably predicted, but scientists can still monitor certain signs that could indicate that an earthquake is likely
2) Lasers can be used to detect the movement of tectonic plates before an earthquake
3) Vibrations in the Earth’s crust can be monitored using seismometers. If vibrations increase, it could mean there’s going to be an earthquake
4) Scientists can measure gases that escape from cracks in the crust just before an earthquake
5) Rocks will crack and expand because of the increased pressure just before an earthquake

Question 52

What are the methods for predicting tectonic hazards for volcanoes?

Answer 52

1) Volcanic eruptions can be predicted if the volcano is well-monitored to look for the tell-tale signs that come before a volcanic eruption
2) Things such as tiny earthquakes and changes in the shape of a volcano (e.g. bulges in the land where magma has built up under it) all mean an eruption is likely
3) Thermal imaging cameras can be used to detect changes in temperature around the volcano. Temperatures increase before an eruption
4) Scientists can analyse the gases escaping from a volcano. Volcanoes emit lots of sulfurous gases before an eruption

Question 53

How does long-term planning help to prepare a country for tectonic hazards?

Answer 53

.Wealthier more developed countries can plan for tectonic hazards to help reduce the impacts:

1) Emergency services can train and prepare for disasters,e.g. by practising rescuing people from collapsed buildings or setting up shelters. This will reduce the number of people killed
2) Buildings can be designed to withstand earthquakes,e.g. by using strong materials like reinforced concrete or building special foundations that absorb an earthquakes energy
3) People can be educated so they know what to do if an earthquake happens
4) Governments can plan evacuation routes to get people out of dangerous areas quickly and safely in case of an earthquake or volcanic eruption. This reduces the amount of people killed or inured by things such as fire,pyroclastic flows or mudflows.
5) Emergency supplies like blankets, clean water and food can be stockpiled. If a natural hazard is predicted the stockpiles can be moved close to areas likely to be affected

Question 54

How is short-term relief needed after a disaster?

Answer 54

.Short-term relief deals with the immediate impacts of a tectonic hazard. Well-prepared countries are better able to:

1) Provide food and drink and shelter to evacuated people
2) Treat people who have been injured to prevent deaths
3) Recover dead bodies to prevent the spread of disease
4) Rescue people who have been trapped or cut off by damage to roads or bridges
5) Provide temporary supplies of gas, electricity and communications systems if regular supplies have been damaged

Question 55

Explain how some countries are more prepared for tectonic hazards than others using a case study

Answer 55

.Preparedness for tectonic hazards is different in countries of contrasting wealth and development

.Japan(a developed country) and Pakistan (a developing country) have a long history of earthquakes, and both countries have different levels of preparedness

Question 56

How is Japan prepared for tectonic hazards?

Answer 56

.Prediction: The Japan Meteorological Agency (JMA) and local governments monitor seismic activity all over the country. If an earthquake is detected, people are warned immediately

.Preparation: Strict building laws help prevent major damage during an earthquake. Buildings are reinforced with steel frames to prevent them from collapsing. High-rise buildings have deep foundations with shock absorbers to reduce vibrations and shaking in the building. Japan has early warning systems to alert residents to earthquakes and tsunamis. High speed bullet trains automatically brake in the event of an earthquake to stop them derailing. Automatic alarms stop mechanical equipment to alert workers and prevent injuries

Long-term planning: Japan’s population is educated on being prepared for earthquakes. Schools carry out drills to teach children what to do if there’s an earthquake.People living in coastal communities practise getting to higher ground or emergency bunkers in the event of a tsunami

Question 57

How is Pakistan prepared for tectonic hazards?

Answer 57

.Prediction: up until recently there wasn’t extensive monitoring of seismic activity in Pakistan. This could mean earthquakes could strike without warning

.Preparation: as a developing country, Pakistan doesn’t have access to the same building materials or technologies as Japan. Many buildings are constructed using wood and cement which are easily destroyed during earthquakes. Up until recently, building laws didn’t include measures of protection against earthquake damage. Even now they’re often ignored when constructing new buildings. Poor communication networks make it difficult to alert the population

.Long-term planning: there are lots of poor,remote settlements in Pakistan that have no education programme for teaching people what to do if there’s an earthquake. Planning evacuations is difficult because there are very few roads and poor communications

Question 58

How have recent earthquakes tested Japan and Pakistan’s preparedness?

Answer 58

Japan:

1) On 11th March 2011 a powerful earthquake struck north-east Japan
2) It measured 9.0 on the moment magnitude scale and triggered a tsunami that overwhelmed the coast and inland areas
3) Japanese scientists had predicted a smaller earthquake to hit the north of the country, but an earthquake of this magnitude was unexpected

Pakistan:

1) On 8th October 2005 Kashmir Pakistan was struck by a major earthquake
2) It measured 7.6 on the moment magnitude scale,causing landslides,rockfalls and huge amounts of destruction
3) Although scientists monitor seismic activity in the area the earthquake was unoredicted

Question 59

Explain what major impacts the earthquake had on Japan

Answer 59

.Primary impacts: thousands of buildings were damaged. The earthquake caused severe liquefaction (where waterlogged soil acts like a liquid). This caused many buildings to tilt and sink into the ground

.Secondary impacts: the earthquake triggered a tsunami which killed thousands of people.Hundreds of thousands of buildings were completely destroyed. Over 230,000 people were made homeless. The tsunami cut off the power supplies to the Fukushima nuclear power plant, causing a meltdown. Road and rain networks suffered severe damage ,e.g. 325km of railway tracks were washed away

Question 60

Explain what major impacts the earthquake had on Pakistan?

Answer 60

.Primary impacts: the Pakistan earthquake caused around 80,000 deaths mostly from collapsed buildings. Tens of thousands of people were injured. Hundreds of thousands of buildings were damaged or destroyed including whole villages.Around 3 million people were made homeless. Water pipelines and electricity lines were broken, cutting off supply

.Secondary impacts:landslides buried buildings and people. They also blocked access roads and cut off telephone lines. Diarrhoea and other diseases spread due to lack of clean water. Freezing winter conditions shortly after the earthquake caused more casualties and meant rescue and rebuilding operations were difficult

Question 61

What was short-term relief like in Japan?

Answer 61

.International aid and search and rescue teams were brought in

.Rescue workers and soldiers were sent to help deal with the aftermath

.Transport and communications were restored a couple of weeks after the earthquake

.Power supplies were restored in the weeks following the earthquake

Question 62

What was short-term relief like in Pakistan?

Answer 62

.The Pakistani army was initially slow to respond to the disaster.Help from India was refused because of political tensions between India and Pakistan. Help didn’t reach many areas for days or weeks and many people had to be rescued by hand without any equipment or help from emergency services. Tents,blankets and medical supplies were distributed although it took a month for them to reach most areas

Question 63

What was long-term planning like in Japan?

Answer 63

.The Japanese authorities gave an advance warning of the earthquake and the tsunami, which gave people time to evacuate and get to higher ground. Despite very strong shaking in Tokyo, not a single building collapsed thanks to buildings designed to prevent earthquake damage. Nobody died on the bullet train network because of the automatic breaking systems

Question 64

What was long-term planning like in Pakistan?

Answer 64

.Fault lines in the Himalayas were poorly monitored, which meant the Pakistan earthquake was unpredicted. The absence of building laws meant that buildings weren’t reinforced and were extremely vulnerable to damage from earthquake shaking. Most buildings had been constructed using poor quality materials,e.g. cement made from sand which crumbed during the earthquake