IGCSE Theme 2 The Natural Environment Case Studies Flashcards
Describe the cause of the 2011 Tohoku Earthquake
On March 11th 2011, a magnitude 9.0 earthquake occurred off the north-east coast of the main island, Honshu. This was related to the destructive plate boundary where the oceanic Pacific plate and the continental Eurasian Plates collide.
The plates move towards each other at a rate of 83 mm a year. When the earthquake happened the seabed moved 50m sideways and rose by 7m.
The earthquake epicentre was beneath the Pacific Ocean, 129 km east of the port of Sendai and 373 km north of the capital city, Tokyo. The depth of the focus was relatively shallow at 32km.
There were a series of large foreshocks over the previous two days and major aftershocks. The amount of energy released in this single earthquake was 600 million times the energy of the Hiroshima nuclear bomb.
Describe the effects of the 2011 Tohoku earthquake on people
Death – Some 15,894 people died (8% directly related to the earthquake e.g. building collapse and 92% by drowning in the subsequent tsunami).
Economic Impact – The earthquake was the most expensive natural disaster in history, with an estimated cost of US$235 billion. This includes the loss of buildings, infrastructure and business premises and disruption.
Tsunami: The earthquake triggered a tsunami which was up to 40 m high. It passed over the defensive sea wall and caused great destruction inland.
Nuclear disaster – Seven reactors at the Fukushima nuclear power station experienced a meltdown from the impact of the earthquake and tsunami. An evacuation zone affecting 200,000 people was set up.
Describe the effects of the 2011 Tohoku earthquake on the natural environment
Landfall – some coastal areas experienced land subsidence as the earthquake dropped the beachfront in some places by more than 50 cm.
Wildlife - The earthquake and tsunami devastated coastal species. About 110,000 Laysan and black-footed albatross chicks were killed by the tsunami.
Agriculture and plants – Saltwater damage of agricultural lands as a result of the tsunami was so severe that agricultural crops could not be grown on large parts of the tsunami-inundated farmlands even two years after the disaster. This also affected plant life more generally as many species were unable to grow due to the salinity of the soil.
Explain how earthquakes are managed in Japan
Practicing for earthquake emergencies: Disaster Prevention Day - Every year on 1st September an earthquake and tsunami drill takes place to make sure that the rescue and emergency services know how to respond.
Early Warning Systems: The Earthquake Early Warning System was activated one minute before the earthquake and this saved many lives. The system sends a message to mobile phones and is broadcast on TV and radio. Japan Meteorological Agency also issued tsunami warnings three minutes after the earthquake. 58% of people living in coastal areas responded by heading for higher ground.
Search and Rescue: Rescue workers and around 100,000 members of the Japan Self-Defence Force were dispatched to help with search and rescue operations within hours of the earthquake striking and the tsunami hitting the coast. Although many search and rescue teams focused on recovering bodies washing up on shore following the tsunami, some people were rescued from under the rubble with the help of sniffer dogs.
Improved Tsunami barriers - The original 12m tsunami barriers were replaced with ones that were 18m high. However, some scientists have noted that this would still not protect property if a similar earthquake was to take place.
Describe the cause of the 2018 Volcan de Fuego, Guatemala, eruption
Volcán de Fuego in Guatemala is a stratovolcano. Its 2018 eruption on the 3rd June was the deadliest in the 21st century.
Volcán de Fuego is situated at a destructive plate margin where the Cocos plate and Caribbean plate meet. Here, the denser oceanic plate – the Cocos plate – subducts underneath the Caribbean plate. The Cocos plate moves at a rate of around 67mm a year. This occurs due to slab pull – the denser plate sinks into the mantle under the influence of gravity, pulling the rest of the plate along behind it.
As the Cocos plate subducts, it melts due to intense friction in the subduction zone and the heat of the mantle. This leads to a build up of pressure. In 2018, this pressure built up to such an extent that the volcanic eruption occurred with the magma being forced through the volcano’s vent. The eruption included lahars, pyroclastic flows, and clouds of volcanic ash.
Outline the opportunities of living near the Volcan de Fuego
Agriculture: Agricultural production makes up a large part of the economy – the soil is extremely fertile. Dominant crops include coffee beans. Over 17,000 people farm the slopes.
Tourism: As it is the most active volcano in Central America it attracts thousands of visitors each year to observe its violent eruptions. Tourism provides jobs for locals such as being tour guides. A day hike costs $65 a person.
Hot Springs: There are numerous hot springs around the area. People visit these for relaxation as well as drawing in further tourism.
Outline the hazards the Volcan de Fuego presents for people
Ash: The ash cloud from the eruption reached a height of 10km (33,000ft). The ash fall produced by this buried nearby villages and forced the La Aurora International Airport to shut down. In some areas, volcanic ash was 8-10m thick. 115 km2 was covered in ash.
Pyroclastic flows: The pyroclastic flow was estimated to be around 1000°C and travelled at speeds of over 100mph. This was responsible for the majority of casualties and crop damage.
Lahars: Lahars are a type of debris flow composed of a slurry of pyroclastic material, rock debris and water. Heavy rainfall during the eruption led to the formation of lahars. On 9 June, additional lahars prompted preventive evacuations.
Describe the effects of the 2018 Volcan de Fuego eruption on people
Death: 446 people were estimated to have been killed (though some claim it up to 2900). The most common cause of death was asphyxia, followed by burns.
Agricultural Loss: The volcanic material also destroyed an estimated 21,000 acres (8,500 hectares) of corn, bean, and coffee crops.
Building Damage: El Rodeo, a town 35 kilometres southwest of Guatemala City, was completely covered with deep hot ash.
Infrastructural Damage: Ashfall forced the shutdown of La Aurora International Airport, the country’s primary airport.
Describe the effects of the 2018 Volcan de Fuego eruption on the natural environment
Vegetation: With pyroclastic flows covering over 8km, all vegetation in its way was destroyed.
Wildlife: Wildlife including monkeys (such as the Guatemalan black howler) and donkeys were found by rescuers with burns or blinded by the eruption.
Soil Fertility: In the long-term, weathering of the ash will help to renew the fertility of the soil which provides over 17,000 people with a livelihood in the area.
Explain how Guatemala manages the impacts of volcanic eruptions
Monitoring: The volcano was monitored by only one seismometer. Although this provides useful information about movement of magma a range of methods should be used such as tilt meters and gas monitors. The evacuation thus only began as the volcano erupted.
Evacuation: The eruption prompted the evacuation of about 3,100 people from nearby areas with temporary shelters set up for them. Many shelters were in schools such as the Murray D Lincoln school.
Search and rescue: Emergency services, including firefighters, were included in search and rescue attempts in surrounding villages and towns such as El Rodeo. These began two hours after the eruption.
Training: Nearly 800 people have participated in volcanic resilience capacity building and training activities in Guatemala since the Fuego eruption. This included educating and training communities on how to respond to volcanic threats, including evacuation procedures, emergency shelters, and communication plans.
Describe and explain the opportunities presented by the Indus River
Water supply: The Indus and its tributaries are the main water supply for Pakistan’s population of over 220 million.
Agriculture: Rainfall in the southern parts of the country is less than 250 mm per year but there are rich alluvial soils. There is a complex irrigation network of dams and canals, including the 1350m long Guddu Barrage. Pakistan is one of the world’s top ten producers of wheat and cotton.
Hydroelectricity: For example, the Taunsa Barrage near Dera Ghazi Khan produces 100,000 kilowatts of electricity - this is vital for urban centres and heavy industry.
Fishing: This is particularly important in the Sindh area. Palla fish is a delicacy for people living along the river with Sukkur, Thatta, and Kotri being the major fishing centres. Fish farming of pomfret and prawns is important in the delta.
Explain the causes of flooding along the Indus river
Monsoon rains: In the summer of 2022, as U.N. Secretary-General António Guterres put it, “the monsoon was on steroids”: Pakistan received 190% of its normal rainfall in July and August.
Deforestation: Rapid deforestation has taken place since the 1990s. It is estimated that only about 5% of Pakistan is covered by forests now. This has caused soil erosion and more sediment has been transported down the river, blocking the channel. Deforestation also means less interception so surface run-off increases and quickly inundates the river channel during periods of heavy rainfall.
Global warming and Glacial Melt: could mean more glacial melting and more intense monsoon rains. A study published by Columbia University in 2019 found that Himalayan glaciers melted twice as quickly in 2000-2016 as they did from 1975 to 2000.
Artificial levees: These barriers prevent the rivers from bursting their banks in extreme floods. However, because the Indus is choked with sediment from erosion in the Himalayas, building levees has caused the river channel to silt up, causing even bigger floods when the levees break.
Explain the impacts of Indus river flooding
Displacement: In 2022, 33 million people were displaced from their homes.
Agricultural loss: In 2022, the floodwaters covered roughly 10% of Pakistan’s land area. This included 2 million acres of crops. The analysis indicated expected production losses of 88% for cotton and 80% for rice. 1 million livestock were killed.
Infrastructure damage: In 2022, damage occurred to roads, railways, bridges, the electricity network, and the irrigation system. 13,000 kilometres of roads and 400 bridges were destroyed.
Death: In 2022, 1700 people died directly from the floods. People were killed by drowning or electrocution, or they were crushed when walls or buildings collapsed on them.
Explain how the impacts of river flooding are managed along the Indus River
Artificial levees: Artificial levees provide the bulk of the flood protection infrastructure in the Indus Basin. These increase the capacity of the channel and thus reduce flood risk. 6,800km of artificial levees have been built since 1960 to protect the main towns and important infrastructure. At some locations, construction has caused sedimentation of the riverbed, which may require a continuous increase in the heights of the levee. However, the height of levees is fixed at 1.8 metres here, though some areas need higher levees to prevent flooding.
Dams: The Mangla and Tarbela reservoirs are used to regulate flood flows. The Tarbela Dam has a storage capacity of over 11 billion cubic metres of water, which can be used to regulate the flow of water during heavy rainfall events and reduce the severity of downstream floods.
Dredging: In 2021, dredging was carried out in the river Jhelum (a tributary of the Indus) in response to devastating floods. The carrying capacity of the river was enhanced by 25%, reducing the risk of future flooding. Making the channel deeper increases its capacity and makes it less likely to overflow.
Disaster Risk Reduction: A new national plan put into action in 2017, aims to reduce the risks schools, teachers and students face by improving construction standards for schools, creating disaster management plans and holding evacuation drills. Disaster risk reduction has also become a focus in school curriculums.
Explain the opportunities present at the Holderness Coast
Tourism: The beaches of the Holderness Coast attract around 1 million people each year. Seaside tourism has been estimated to support 3,500 jobs and contributes an estimated £56m to the local economy. This is vital in areas such as Hornsea where 1 in 5 jobs are in the tourist industry.
Energy: The Easington Gas Terminal is one of three main gas terminals in the UK, and is situated on the Holderness Coast. Around 20% of Britain’s imported gas from Norway is brought ashore via a huge 1,200km long underwater pipe known as the Langeled pipeline. Once captured at Easington, the Norwegian gas is then transferred into the UK’s national supply network. This would be very costly to move or repair if damaged.
Fossil Exploration: The Holderness coast is well known for fossils due to the geology of glacial till in the area. A 180 million year old ammonite was discovered in 2020.
Fishing: The Holderness Coast is mostly known for its shellfish. Bridlington, a major town along the Holderness Coast, is now the most important port in the UK and Europe for lobster landings. In 2014 local fishermen caught 420 tonnes of lobster worth £4m.
