Plate Tectonics

Question 1

Natural Hazard

Answer 1

Naturally occurring event that threatens human lives and causes damage to properties

Question 2

Characteristics of core layer

Answer 2

Approximately 1400 km thick, the inner core is in solid state due to extreme pressure exerted on it. The outer core is in liquid layer of approximately 2100 km thick. The core is composed mostly of iron and nickel. The temperature in the core is estimated to be between 3000C and 5000C

Question 3

Characteristics of mantle layer

Answer 3

The mantle occupies 80 percent of the earth’s total volume and is approximately 2900 km thick and is made up mostly of solid rocks that flow under high temperatures and pressure. Its temperature ranges between 800C and 3000C

Question 4

Characteristics of crust layer

Answer 4

The crust is the earth’s outermost layer and is also the Earth’s surface. It is less than 1% of the Earth’s volume. The crust is made up of the oceanic and continental crust. The crust can range in thickness from a few km to more than 70 km. Hot molten rocks known as magma is formed when the rocks in the lithosphere melt.

Question 5

Oceanic and Continental Plates

Answer 5

Oceanic plates are made up of denser basaltic rocks and are beneath deep oceans. Its thickness is about 5 to 8 km and it is denser than continental plates.
Continental plates are made up of less dense granitic rocks and is beneath the earth’s continental land masses and under shallow seas close to continents. Its thickness is about 30 to 70 km and is less dense than oceanic plates.

Question 6

Main plates

Answer 6

Pacific plate
North American plate
Nazca plate
South American plate
African plate
Eurasian plate
Indo-Australian plate
Antarctic plate

Question 7

Convection currents

Answer 7

Convection currents are movements of heat within the mantle. Material in the mantle is heated by the core, causing the mantle material to expand, rise and spread out beneath the plates. This causes plates to be dragged along and to move away from each other. Then, the hot mantle material cools slightly and sinks, pulling the plates along. The sinking mantle material heats up again as it nears the core and the whole process repeats.

Question 8

Slab-pull Force

Answer 8

Slab-pull force occurs when a denser oceanic plate is forced beneath a less dense continental plate or oceanic plate in a process called subduction. As the plate subducts, it pulls the rest of the plate along. The subducting or sinking plate drives the downward-moving portion of convection currents. The mantle material which is found away from where plate subducts drives the rising portion of convection currents.

Question 9

Continental-Continental plate divergence

Answer 9

Convection currents cause two continental plates to move apart, forming a divergent plate boundary. The two continental plates are stretched, causing fractures to be formed at the plate boundary. As the crust continues to be pulled apart, the land in between the two continental plates sink, forming a linear depression known as a rift valley. The remaining highland next to the rift valley is known as a block mountain. An example is the East African Rift Valley, formed when the Nubian boundary of the African plate moved away from the Somalian boundary of the African plate. A number of active volcanoes and earthquake fractures can also be found along the East African Rift Valley.

Question 10

Oceanic-Oceanic plate divergence

Answer 10

Convection currents cause two oceanic plates to move apart, forming a divergent plate boundary.
This causes fractures at the plate boundary. Magma rises from the mantle through the fractures to fill the gap between the plates and creates a ridge of new sea floor. This process is sea-floor spreading where the lave cools and solidifies after flowing out into the sea-floor. A mid-oceanic ridge is formed eventually, which is a central ridge structure that divides ocean basin in half. At various points along the mid-oceanic ridge, magma builds up and solidifies to form undersea volcanoes. When these volcanoes eventually grow above sea level, they are known as volcanic islands. An example is the Mid-Atlantic Ridge in the middle of the Atlantic Ocean, formed when the North American Plate and the Eurasian Plate moved away from each other.

Question 11

Oceanic-Oceanic plate convergence

Answer 11

Convection currents cause two oceanic plates to move towards each other, forming a convergent plate boundary. The denser oceanic plate subducts under the less dense oceanic plate, forming a subduction zone. At the subduction zone, a depression in the sea floor called an oceanic trench is created. At the same time, the denser subducting plate causes mantle material above it to melt, forming magma. The magma rises through cracks in the crust to form undersea volcanoes. Eventually, the magma rises above the sea level to form a chain or arc of islands. Earthquakes may also occur at the boundary between the two plates due to the layer of rocks of the two plates rub against each other due to subduction. An example is the Pacific Plate converging with the slower-moving Philippine plate, where the Pacific Plate subducts beneath the Philippine Plate, forming the Mariana Trench and the Mariana Islands.

Question 12

Continental-Continental plate convergence

Answer 12

Convection currents cause two continental plates to move towards each other, forming a convergent plate boundary. As both plates are too thick and buoyant, they collide with one another and resist subduction. This causes the plates to break and slide along fractures in the crust. Layers of rocks in the upper part of the continental crust are then compressed together and fold upwards or sideways, creating fold mountains. An example is the Himalayas, formed by the convergence of the Indian plate and Eurasian plate.

Question 13

Oceanic-Continental plate convergence

Answer 13

Convection currents cause an oceanic plate and a continental plate to move towards each other, forming a convergent plate boundary. The denser oceanic plate subducts under the less dense continental plate. At the subduction zone, a depression in the sea floor called an oceanic trench is created and layers of rocks in the upper part of the continental crust are compressed together and folded, creating fold mountains. At the same time, the denser subducting plate causes mantle material above it to melt, forming magma. The magma rises through cracks in the crust to form active volcanoes. An example is the Sunda trench and Barisan Mountains, formed when the Australian plate subducts under a section of the Eurasian plate.

Question 14

Transform plate movement

Answer 14

Plates slide past each other along transform plate boundaries. This movement results in the formation of a transform fault. In the process, tremendous stress builds up and is eventually released, often in the form of violent earthquakes. An example is the San Andreas Fault between the Pacific Plate and the North American Plate.

Question 15

Comparison of fold mountains and block mountains

Answer 15

Both are formed at continental-continental plate boundaries. Block mountains are formed at divergent plate boundaries while fold mountains are formed at convergent plate boundaries. Fold mountains tend to be taller than block mountains. Fold mountains are formed by folding while block mountains are formed by faulting.

Question 16

Fold Mountains

Answer 16

Over million of years, layers of rocks when compressed and folded form fold mountains. Fold mountains can grow to impressive heights and lengths such as the Himalayas. Fold mountains are formed along convergent plate boundaries where plates move towards each other and collide. The resultant compressional force creates immense pressure which causes the layers of rocks to buckle and fold. This process is known as folding. The upfold is called the anticline and the downfold is known as the syncline. When there is increasing compressional force on one limb of a fold, the rocks may buckle until a fracture forms. The limb may then move forward to ride over the other limb.

Question 17

Rift Valley and Block Mountains

Answer 17

River valley and block mountains are formed at divergent plate boundaries where plates are pulled apart, giving rise to faults. A fault is a fracture in the rocks along which the rocks are displaced. The tensional forces from these movements result in parts of the crust being fractured. This process is called faulting. Along these faults, sections of the crust can extend. A rift valley is a valley with steep sides that is formed when sections of the crust extend along fault lines. The central block off land subsides between two parallel faults due to tensional forces. The sections which are left standing beside the rift valley are block mountains.

Question 18

Volcanoes

Answer 18

A volcano is a landform formed by magma ejected from the mantle onto the earth’s surface. Magma is molten rock found below the earth’s surface and builds up within the crust to form a magma chamber, which is a reservoir of molten rock beneath the earth’s crust. Volcanoes can be found at divergent and convergent plate boundaries where there is subduction. At these subduction zones, magma rises and accumulates in the magma chamber, where pressure builds up until the magma forces its way onto the earth’s surface through vents. Vents are openings in the earth’s surface with a pipe leading into the magma chamber. Magma that is ejected onto the surface is known as lava, which builds up around the vent to form a volcano.

Question 19

Shield Volcanoes

Answer 19

Shield volcanoes have gently sloping sides and a broad summit. These volcanoes are formed when low-silica lava has been ejected. Low-silica lava flows easily and spreads out over a large area before solidifying. Since the lave does not trap much gas, eruptions are usually not explosive. With successive eruptions, the base of the volcano increases in size as lava accumulates. Shield volcanoes are common near divergent plate boundaries where magma can rise directly from the mantle. An example is Mount Washington in the United States of America.

Question 20

Stratovolcanoes

Answer 20

Stratovolcanoes develop from successive eruptions of lava and ash. Ash deposits can also contain coarser rock fragments ejected from the vent. After an initial eruption, the subsequent eruption ejects lava which covers the soft ash and prevents it from being eroded away. Over time, successive eruptions build a high volcano with a slightly concave profile, which means the volcano is steeper at the top and gentler at the base. Secondary cones may develop as magma from the vent seeps into the sides of the cone and erupts. Pyroclastic flow and lahars may result from volcanic eruptions. Pyroclasts refer to hot rock fragments and super heated gases ejected during a volcanic eruption. The movement of such rock fragments and gases down the slopes of an erupting volcano is known as pyroclastic flow. Lahars refer to a mixture of pyroclasts and melted ice from the mountains, which are wet volcanic debris flowing down the slopes of an erupting volcano. The eruptions of Mount Pinatubo, a stratovolcano in the Philippines in 1991, emitted 10 million tonnes of lava, 20 million tonnes of sulfur dioxide and millions of tonnes of ash. It was the second largest volcanic eruption that occurred on land in the 20th century.

Question 21

Massive destruction by volcanic materials

Answer 21

When an volcano erupts, lava and pyroclasts are released that consists of ash, rock fragments and volcanic bombs. These volcanic materials can cause widespread damage of property. Lava of high temperatures between 500C and 1400c can burn down the areas it flows through. Low-silica lava flows easily and quickly over long distances and can destroy larger areas. A pyroclastic flow contains hot rock fragments ranging from ash to boulders. It moves at speeds of more than 80km/h and damages everything in its path. When people breathe in hot ashes and gases, they can suffer serious injury or even die. The large volcanic bombs of heated rocks can destroy property in the area where they fall. The ongoing eruption of Kilauea in Hawaii has damaged many houses and infrastructure since 1983. This causes loss of lives, homelessness and economy impact as people and government need to pay for repairs.

Question 22

Landslides

Answer 22

Landslides can occur due to the structural collapse of a volcanic cone during a volcanic eruption. Large scale landslides can block the flow of river and result in flooding, road blockage and bury villages and farmlands. In 1995, a pyroclastic flow from the eruption of Nevado del Ruiz in the Andes mountains of South America triggered lahars which buried the town of Armero and killed more than 20 000 people. This causes loss of lives, homelessness and economy impact as people and government need to pay for repairs.

Question 23

Pollution

Answer 23

A volcanic eruption can release ash particles which can disrupt human activities over large distances from the volcano. This is because fine ash particles of less than 0.001 mm can spread easily over thousands of km by winds to affect areas further away from the eruption source. When thick plumes of ash settle on the ground, they can block sunlight, suffocate crops and trigger severe respiratory problems in humans and animals. Volcanic eruptions can release various gases such as CO2, SO2, H2 and CO which are harmful to people. In 2010, the eruption of Eyjafjallajökull in Iceland emitted large amounts of volcanic ash clouds containing tiny particles of abrasive glass, sand and rock. These tiny particles can damage aircraft engines and structures. This caused the extensive closure of air space in many European countries. The airline industry suffered economic losses of about US$1.8 billion due to worldwide connecting flight cancellation.

Question 24

Fertile soil

Answer 24

When lava and ash from volcanic eruptions break down, they form fertile volcanic soils and can support agriculture. Volcanic rocks contain minerals. However, these minerals in the newly formed rocks are not available to plants. After they are weathered and broken down for a very long period of time, the minerals will then be available to plants. many people have been living near the volcanic areas in Java and Bali because the fertile volcanic soils support the cultivation of crops such as tea, coffee and rice. The soils remain fertile than in most non-volcanic areas even after many rounds of cultivation.

Question 25

Previous stones and minerals

Answer 25

Magma rising from deep inside the earth contains a range of previous stones and minerals. They can be extracted after the upper layers of volcanic rocks have been eroded millions of years ago. Diamonds are an example of precious stones from volcanic rocks. They are formed from the heated and pressurised carbon which are cooled in magma pipes beneath the earth’s surface. The refined diamonds are useful as industrial tools, in scientific research and for making jewellery. Volcanic rocks are also a rich source of building materials and the production of other daily useful items. The old volcanic rocks in Kimberley in South Africa are one of the world’s richest sources of diamonds. These precious stones and minerals are formed after millions of years, where they are dug out and sold for income.

Question 26

Tourism

Answer 26

Volcanic areas can attract millions of tourists as there are a variety of activities conducted in these areas for example, camping, hiking or enjoying the scenery. Volcanic areas may also be rich in history that can encourage people to come and learn more about these areas. In 79 CE, huge plumes of volcanic ash from the eruptions of Mount Vesuvius buried the Roman city of Pompeii. As the ash buried the city in its entirety, it has helped preserve entire buildings, painting and artefacts. The place receives about 3 million visitors a year. The natural scenery and history attract many tourists, which provide income for locals involved in the tourism industry

Question 27

Geothermal energy

Answer 27

Geothermal energy is energy derived from the heat in the earth’s crust. When groundwater is heated up by hot rocks beneath the surface, it erupts as hot water or steam. The hot water or steam is then used to drive turbines or produce electricity. In Iceland, almost two-thirds of the electricity supply is produced from geothermal energy due to the presence of the large number of volcanoes. More than 70% of homes in the country are heated by volcanic steam. heat from volcanoes can be used to turn turbines and generate electricity for people to use.

Question 28

Earthquake

Answer 28

An earthquake is a vibration in the earth’s crust caused by the sudden release of stored energy in the rocks along fault lines. Plate movements cause the slow build-up of stress on the rocks at the fault and when rocks can no longer withstand the increasing stress, they suddenly slip many metres, causing an earthquake.

Question 29

Magnitude

Answer 29

The magnitude of an earthquake refers to the amount of energy released by the earthquake. The magnitude of an earthquake is measured by the Ritcher Scale. The greater the magnitude on the Rictcher Scale, the greater the impact of the earthquake on the land. The impact of an earthquake is 10 times greater for each increasing magnitude on the Ritcher Scale. However, earthquakes of greater magnitude may not always result in extensive damage and destruction. There are other factors that can affect the extent of damage and destruction by earthquakes. In Tohuku, Japan, a 9.0 magnitude earthquake in 2011 had a death toll of 28000 people. However, in Haiti, a 7.0 magnitude in 2010 had a death toll of more than 300 000 people. The greater the amount of seismic energy received, the more shaking of the ground, resulting in more destruction.

Question 30

Population Density

Answer 30

Population density refers to the number of people living in a particular area. There are more people in a highly populated area than in a sparsely populated area. Therefore, an earthquake in a city is likely to cause more casualties than in a countryside. Higher population density suggests more tall buildings which could collapse, causing greater destruction.

Question 31

Level of Preparedness

Answer 31

The level of preparedness is the amount of preparation taken by the authorities and citizens to reduce the impact of an earthquake. The preparations include evacuation plans, trained rescue workers and other action plans. When people are well-prepared, they are able to cope with the aftermath of the earthquake and reduce its impact.

Question 32

Distance from the epicentre

Answer 32

When an area is close to the epicentre of an earthquake, it is likely to suffer extensive damage than places further away from it. The city centre of Christchurch in New Zealand experienced extensive damage by an earthquake in 2011 than places away from the city because the city was close to the epicentre. When the people are nearer to epicentre, they experience more seismic energy resulting in more shaking of the ground and more destruction.

Question 33

Time of Occurrence

Answer 33

The time of occurrence of an earthquake determines people’s activities at that time and affects their chances of survival in the earthquake. When an earthquake occurs during the time when most people are sleeping, there is a higher chance of many people being trapped and killed by collapsed houses. When the earthquake occurs in the city during the day, many people will be affected as they would be working or going about their daily lives there. An earthquake occurred after midnight in the Sun Moon Lake Region in Taiwan in 1999 and killed more than 2400 people.

Question 34

Type of Soil

Answer 34

The seismic waves released from an earthquake can be amplified in places with loose and unconsolidated sediments, so these places can experience greater damage caused by the earthquake. Buildings built on saturated and unconsolidated sediments can be damaged by liquefaction, which is a situation when the ground becomes unstable and the saturated soil flows like a liquid. After the earthquake in Christchurch in 2011, many houses and buildings became unsafe to occupy due to the threat of liquefaction.

Question 35

Threat of Tsunamis

Answer 35

Tsunami is a series of great sea waves caused by an earthquake, landslide or volcanic eruption occurring underwater. Seismic energy from an offshore earthquake forces out a large amount of sea water. The height of the initial tsunami waves is less than 1m. They travel very fast and may pass undetected. When reaching the coast with shallower water, the waves slow down due to friction, causing the waves to increase in height as they are pushed forward by the waves behind them. The tsunami waves hit the shore with a powerful force and this results in extensive damage. In 2004, a 9.2 magnitude earthquake in the Indian Ocean triggered a tsunami, which destroyed the coastal communities in 12 countries. The low-lying coastal areas of Western Sumatra in Indonesia, including the city of Banda Aceh, experienced great destruction as far inland as 10 km by the tsunami waves with heights ranging from 4 to 39 m. People were washed away and buildings were destroyed by the waves, causing loss of lives and homelessness. The government will also need to spend lots of money to rebuild the area.

Question 36

Disruption of essential services

Answer 36

Earthquakes can disrupt basic services such as the supply of water, electricity and gas in the affected area. The vibrations caused by earthquakes can snap pipes and break cables to trigger the outbreak of fires. Communication services such as television broadcasts and telephone connections can also be interrupted. In Kobe, Japan, the earthquake in 2004 damaged pipes and transmission lines, affecting about 1 million residents in the city and they had no access to basic services. There is a lack of clean water to drink, resulting in people drinking contaminated water and getting water-borne diseases. There is also no electricity and gas to their daily lives.

Question 37

Landslides

Answer 37

The vibrations caused by earthquakes can weaken the slopes of hills and mountains and make them become unstable. The unstable slopes may result in landslides. Landslides are rapid movements of rock, soil and vegetation debris down a slope. Their length and width can range from several metres to kilometres. Earthquakes can also trigger mudflows when heave rainfall saturates the soil and cause the mixed soil debris to flow down a slope. In 1970, an earthquake off the coast of Peru triggered a massive landslide, which travelled at a speed of more than 160km/h and buried the town of Ranrahirca within seconds. More than 18000 people were killed and only 2000 people survived the disaster. This causes homelessness, loss of lives and affected the people’s businesses and daily lives.

Question 38

Destruction of properties

Answer 38

The vibrations caused by earthquakes can destroy homes and make people become homeless. People may have to stay at temporary shelters for a significant period of time before their homes are rebuilt completely. In Tohuku, Japan, the 2011 earthquake caused extensive structural damage that left many people homeless because their homes became unsafe to live in. This causes a severe shortage of housing and concerns about the long-term consequences on the health of the people. Businesses and people’s daily lives are affected.

Question 39

Destruction of Infrastructure

Answer 39

Earthquakes may cause cracks to form in infrastructure such as roads and bridges. This can disrupt transport routes as they become unsafe to use. The 1995 earthquake in Kobe, Japan, damaged the infrastructure and caused many places in the city to become inaccessible. Japan’s total cost of repair after the earthquake in Tohoku was US$300 billion. This causes businesses and people’s daily lives to be affected.

Question 40

Land Use Regulaions

Answer 40

Land use regulations are a set of rules implemented to restrict developments in certain areas. There is also prohibition of constructing new buildings on low-lying lands which are vulnerable to tsunamis.

Land use regulations are enforced in California, USA, to restrict new buildings being constructed across fault lines or areas at risk of liquefaction to minimise the damage caused by earthquakes. Liquefaction can also occur when vibrations of an earthquake cause saturated soil in an area to flow like a liquid. This makes the area become unstable and unsafe for development.
By not having developments near high risk areas, in the event of on earthquake or tsunami, fewer buildings will be damaged. Fewer developments mean reduced populations, which also lead to fewer deaths as a result of earthquakes.
However, they may not be implemented easily in existing built-up areas or privately owned land. Some residents or private owners may not be willing to relocate because they believe that another hazard would not happen. The governments may buy land from private owners or compensate those who need to relocate in order to implement protective measures in the risk areas, which can be very costly.

Question 41

Infrastructure

Answer 41

Effective building design can reduce the collapse of buildings and minimise the damage caused by an earthquake. The government can install damping services in buildings to act as shock absorbers for some of the seismic energy released during an earthquake. As they act as a counterweight which moves in the opposite direction to the motion of the earthquake, the swaying motion of the building is thus reduced, possible preventing the collapse of the building.
For example, Taipei 101 has a damping device made of heavy bars which reduces its susceptibility to earthquakes. Base isolation bearing can also be placed between the ground and the building. These bearings can act as a buffer to avoid excessive shaking during an earthquake, thus preventing them from collapsing.
The benefits of this include a lower death toll, faster rescue and evacuation efforts as well as lower costs in re-building the affected areas.
However, effective building designs may increase both the costs of construction and maintenance to withstand potential earthquakes. It is also extremely expensive to implement reinforced infrastructure which can resist earthquakes.

Question 42

Emergency Drills

Answer 42

Emergency drills are a form of preparedness measure where people practise the necessary actions to take during earthquake events.
In Japan, emergency drills are carried out on 1 September since 1960 to commemorate Disaster Prevention Day by simulating a high-magnitude earthquake. These drills prepare the people mentally to react when earthquakes occur. Emergency vehicles learn how to move about to seek alternative routes to reach the affected areas when main roads are likely to be blocked by fallen objects or damaged.
Emergency drills raise people’s awareness and reduce levels of panic and irrational behaviour when a disaster strikes. People learn from the drills on how to get themselves to safe locations, follow instructions given by trained personnel and carry out first-aid. Some of them can also become members of local response teams to help people during earthquake events.
Emergency drills may be designed based of the most serious earthquake event which took place. However, the 2011 earthquake in Tohoku, Japan, was on a scale never experienced before in the country, so the drills and evacuation plans became inadequate to cut down the extensive damage caused by the earthquake. Emergency drills may not be effective when there is not enough time for people to evacuate because it is difficult the predict the onset of an earthquake.

Question 43

Earthquake monitoring and warning systems

Answer 43

Monitoring and warning systems are technological devices that enable scientists to predict potential hazards and to warn people so that they can prepare for evacuation. By studying the history or timeline of the occurrence of earthquakes, scientists can monitor earthquakes or develop the seismic risk maps. The installation of earthquake sensors in earthquake-prone zones helps monitor the frequency of vibrations and detect possible development of an earthquake.
Earthquake motion data is gathered from hundreds of observation stations installed on bridges and roads in Japan.
Monitoring earthquakes allows scientists to estimate the frequency and magnitude at particular fault lines so that the occurrence of an earthquake can be predicted. Seismic risk maps developed from these studies are useful to identify places that are likely to be at risk from earth movement or liquefaction. The installed earthquake sensors in the observation stations can monitor ground motion and predict the occurrence of an earthquake. These sensors can also help estimate damage to bridges, railways or other infrastructure quickly.
However, earthquake sensors are expensive to obtain, install and use. Furthermore, a earthquake usually occurs seconds after a warning is sounded. Therefore, warnings may not provide sufficient time for an evacuation. Noise, lightning or device failure may interfere with the seismograph and result in false warnings being given. It is also difficult to give accurate warnings when multiple earthquakes occur close to each other.

Question 43

Earthquake monitoring and warning systems

Answer 43

Monitoring and warning systems are technological devices that enable scientists to predict potential hazards and to warn people so that they can prepare for evacuation. By studying the history or timeline of the occurrence of earthquakes, scientists can monitor earthquakes or develop the seismic risk maps. The installation of earthquake sensors in earthquake-prone zones helps monitor the frequency of vibrations and detect possible development of an earthquake.
Earthquake motion data is gathered from hundreds of observation stations installed on bridges and roads in Japan.
Monitoring earthquakes allows scientists to estimate the frequency and magnitude at particular fault lines so that the occurrence of an earthquake can be predicted. Seismic risk maps developed from these studies are useful to identify places that are likely to be at risk from earth movement or liquefaction. The installed earthquake sensors in the observation stations can monitor ground motion and predict the occurrence of an earthquake. These sensors can also help estimate damage to bridges, railways or other infrastructure quickly.
However, earthquake sensors are expensive to obtain, install and use. Furthermore, a earthquake usually occurs seconds after a warning is sounded. Therefore, warnings may not provide sufficient time for an evacuation. Noise, lightning or device failure may interfere with the seismograph and result in false warnings being given. It is also difficult to give accurate warnings when multiple earthquakes occur close to each other.

Question 44

Search and Rescue

Answer 44

Search and rescue involves locating and freeing trapped people under collapsed buildings quickly.
For example, after the earthquake in Tohoku, Japan, in 2011, sniffer dogs and heat sensors were deployed and successfully rescued many who were trapped.
This mission is important because it can even save survivors who are trapped without food for a few days.
However, rescue workers have only a limited 72 hours or 3 days to locate the trapped survivors. Many trapped victims are not likely to survive without food and water after three days.

Question 45

Emergency food and medical supplies

Answer 45

It is important to provide immediate medical help to the injured survivors so that they have better chance for recovering. The survivors must also obtain clean drinking water supply before they become dehydrated an to avoid the spread of diseases.
In the 2002 earthquake in Afyon, Turkey, the immediate response from the Turkish Red Crescent Society to supply 20 000 tents, 50 000 blankets and 3000 heaters to the survivors in the affected areas and helped the survivors to cope.
The provision of immediate aid allows the survivors to carry on with their lives easily after a disaster.
When insufficient medical supplies, food and water are provided to large numbers of affected people, the situation may give rise to social unrest.

Question 46

Rebuilding of infrastructure

Answer 46

It is crucial to rebuild and improve infrastructure after an earthquake so that the people in the affected area can resume their normal lives quickly.
After the 1995 earthquake in Kobe, Japan spent billions of dollars to develop technology to build more earthquake-resistant buildings.
The authorities can come up with stricter building codes to ensure the infrastructure being restored at a higher safely level than before.
Reinforced buildings may be able to withstand earthquakes but may not be protected against tsunamis. This requires additional protection in the form of coastal protection structures such as breakwaters.

Question 47

Provision of health care

Answer 47

It is necessary to provide health options for the survivors such as long-term counselling for those who suffered the loss of loved ones, homes or jobs after earthquakes as these incidents could be long-lasting traumas for some.
A year after the 2011 earthquake in Christchurch, New Zealand, the relevant party was able to identify the people of all age groups in the affected areas who developed problems of anxiety and depression. Many health workers were deployed there to help those who are in need of medical attention.
Improving health options, such as restoring the supplies of basic necessities to the people after earthquakes can be very challenging.