Topic 2 - Tectonic Hazards Flashcards
Unit 1: Living with the Physical Environment (Section A - The Challenge of Natural Hazards)
What is an earthquake?
An earthquake is a sudden and violent period of ground shaking, which is most commonly caused by sudden movements of rocks within the Earth’s crust.
Why is there a pattern of earthquakes?
They all occur at plate margins
Why do some earthquakes not occur at plate margins?
They are caused by human activity such as underground mining, reservoir construction or oil extraction.
How thick are tectonic plates?
100 km thick
What are the two types of crust?
- Oceanic crust: dense, thin
- Continental crust: less dense, thick
How do constructive plates move?
The plates move past each other. The build up of friction causes a sudden release which causes an earthquake.
Are there any tectonic hazards at a constructive plate margin?
- No land is created or destroyed
- As magma breaks through the surface, it triggers mild earthquakes
- There are shield volcanoes, as lava erupts and flows a long way before cooling
How do destructive (subduction) plates move?
The plates move towards each other, and the oceanic crust ends up subducting beneath the continental crust, as it is denser.
Why do plates move in relation to one another?
Due to the convection currents deep within the Earth
What is an example of a constructive plate margin?
‘Eyjafjallajokul’ in Iceland
How do destructive (collision) plates move?
The plates move towards each other, and neither are more dense, so they collide with each other.
Are there any tectonic hazards at a destructive (subduction) plate margin?
- The sudden vertical displacement over such large areas, disturb the ocean’s surface, and generate destructive tsunami waves
- There are composite volcanoes, as magma breaks through the surface to form steep-sided volcanoes, where eruptions are violent and explosive
What is an example of a destructive (collision) plate margin?
Himalayas - Indian and Eurasian plates collision
What is an example of a destructive (subduction) plate margin?
West Coast of South America
Are there any tectonic hazards at a conservative plate margin?
- Volcanoes do not form as there is no magma
- Earthquakes happen along this plate margin, as stresses gradually build up over many years. They can be destructive as they are close to the Earth’s surface. These are released when suddenly the plates slip and shift.
Are there any tectonic hazards at a destructive (collision) plate margin?
- As the plates collide, they are forced upwards, and they form fold mountains
- There are very destructive earthquakes, which are caused by plates sticking, so pressure builds up, and there is a sudden release as the plates slip. The secondary effects of an earthquake, can include fires, tsunamis, and aftershocks
- There are no volcanic eruptions here as there is no magma.
How do conservative plates move?
The plate move away from each other
What is an example of a conservative plate margin?
San Andreas Fault in California
What is a volcano?
A large, and often conical-shaped landform usually formed over a long period of time, by a series of eruptions
Where do volcanoes happen?
Like earthquakes, the majority of volcanoes occur in long belts that follow the plate margins, for example around the edge of the Pacific Ocean. This is known as the ‘Pacific Ring of Fire’. There is also a belt of volcanoes through the middle of the Atlantic Ocean. This is the Mid-Atlantic Ridge which includes the Azores and Iceland which are volcanic islands.
Why is there a pattern of volcanoes?
Volcanoes are fed by hot molten rock (magma) from deep within the Earth. This rises to the surface at constructive and destructive plate margins. Volcanoes also form at hotspots, where the crust is thin and magma is able to break through to the surface. The Hawaiian Islands in the Pacific Ocean are a good example of volcanoes forming at a hotspot.
What are some important facts about the Chile earthquake?
- 27 February 2010
- Destructive Subduction - Nazca Plate is moving beneath the South American Plate
- 8.8 magnitude
- Epicentre location: Sea
- 3 minutes long
- Followed by small aftershocks
- Tsunami warnings
- Waves rushed across the Pacific Ocean at 800km/hr
What are some important facts about the Nepal earthquake?
- 5 April 2015
- Destructive Collision, caused by Himalayas formation - Indo-Australian plate colliding with Eurasian plate, at a rate of 45mm/year
- Epicentre Location: Urban towns and villages (80 km northwest of Nepal’s capital Kathmandu)
- Very shallow earthquake - 15 km below Earth’s surface
- Severe ground shaking
- Wide spread landslides
- 7.9 magnitude
- Damage to hundreds of km away, in Pakistan, Tibet and India
- Avalanches
What are the (social) primary effects of the Chile earthquake 2010?
- 500 people killed
- 12,000 people injured
- 500,000 people affected
What are the (economic) primary effects of the Chile earthquake 2010?
- Cost of earthquake estimated at US $30 billion
- 220,000 homes, 4,500 schools, 53 ports, 56 hospitals and other public buildings affected
- Port of Talcahuano and Santiago airport badly damaged
What are the (environmental) primary effects of the Chile earthquake 2010?
Much of Chile lost power, water supplies and communications
What are the (social) primary effects of the Nepal earthquake 2015?
- 9,000 people killed
- 20,000 people injured
- Over 8 million people (a third of Nepal’s population) affected
- 3 million people left homeless when houses were destroyed
- 1.4 million people needed food, water and shelter in the days and weeks after the earthquake
What are the (economic) primary effects of the Nepal earthquake 2015?
- Cost of earthquake estimated over US $5 billion
- 7,000 schools destroyed and hospitals overwhelmed
- International airport became congested, as aid arrived
- 50% of shops destroyed, affecting food supplies and people’s livelihoods
What are the (environmental) primary effects of the Nepal earthquake 2015?
Electricity, water supplies, sanitations and communications affected
What are the (social) secondary effects of the Chile earthquake 2010?
Several pacific countries struck by tsunami - warnings and loss of life
What are the (economic) secondary effects of the Chile earthquake 2010?
- Several coastal towns devastated by tsunami waves
- A fire at a chemical plant near Santiago - area had to be evacuated
What are the (environmental) secondary effects of the Chile earthquake 2010?
Remote communities had been cut off for many days
What are the (social) secondary effects of the Nepal earthquake 2015?
- Avalanches on Mount Everest killed at least 19 people - the greatest loss of life on the mountain in a single incident
- An avalanche in the Langtang region left 250 people missing
- Many people evacuated in case of flooding
What are the (economic) secondary effects of the Nepal earthquake 2015?
- Ground shaking triggered landslides and avalanches, blocking roads and hampering relief efforts
- The earthquake occured on land, so it didn’t cause a tsunami
What are the (environmental) secondary effects of the Nepal earthquake 2015?
A landslide blocked the Kali Gandaki River, 140 km (90 miles) northwest of the capital Kathmandu
What are the immediate responses of the Chile earthquake 2010?
- Emergency services acted swiftly. International help needed to supply field hospitals, satellite phones and floating bridges.
- Temporary repairs made to the important Route 5 north-south highway within 24 hours, enabling aid to be transported from Santiago to affected areas.
- Power and water restored to 90% of homes within 10 days.
- A national appeal raised US $60 million - enough to build 30000 small emergency shelters
What are the immediate responses of the Nepal earthquake 2015?
- Search and rescue teams, water and medical support arrived quickly from countries
such as UK, India and China. - Helicopters rescued many people caught in avalanches on Mount Everest and delivered
supplies to villages cut off by landslides. - Half a million tents needed to provide shelter for the homeless.
- Financial aid pledged from many countries.
- Field hospitals set up to support overcrowded main hospitals.
- 300,000 people migrated from Kathmandu to seek shelter and support with family and friends.
- Social media was widely used in search and rescue operations and satellites mapped damaged areas
What are the secondary responses of the Chile earthquake 2010?
- A month after the earthquake, Chile’s government launched a housing reconstruction plan to help nearly 200,000 households affected by the earthquake.
- Chile’s strong economy, based on copper exports, could be rebuilt without the need for much foreign aid.
- The President announced it could take four years for Chile to recover fully from the damage to buildings and ports
What are the secondary responses of the Nepal earthquake 2015?
- Roads repaired and landslides cleared. Lakes, formed by landslides
damming river valleys, needed to be emptied to avoid flooding. - Thousands of homeless people to be rehoused, and damaged homes repaired. Over 7000 schools to be re-built or repaired.
- Stricter controls on building codes.
- In June 2015 Nepal hosted an international conference to discuss reconstruction and seek technical and financial support from other countries.
- Tourism, a major source of income, to be boosted by July 2015 some heritage sites reopened and tourists were starting to return.
- Repairs to Everest base camp and trekking routes - by August 2015, new routes had been established and the mountain re-opened for climbers.
- In late 2015 a blockade at the Indian border badly affected supplies of fuels, medicines and construction materials.
What is Chile’s GDP per capita?
$25,400 per person
What is Nepal’s GDP per capita?
$3,800 per person
What is Chile’s life expectancy for people?
80 years
What is Nepal’s life expectancy for people?
73 years
What is Chile’s rate for doctors per person?
2.84 per 1,000 people
What is Nepal’s rate for doctors per person?
0.85 per 1,000 people
What is Chile’s adult literacy rate?
97% over 15-year-olds can read/write
What is Nepal’s adult literacy rate?
71% over 15-year-olds can read/write
What is Chile’s access to clean water rate?
100% of people have access to clean water
What is Nepal’s access to clean water rate?
94% of people have access to clean water
What is Chile’s GDP?
US $496 billion
What is Nepal’s GDP?
US $15 billion
What is Chile’s GDP rank (out of 229 countries)?
42nd
What is Nepal’s GDP rank (out of 229 countries)?
86th
What is Chile’s GDP per capita rank (out of 229 countries)?
79th
What is Nepal’s GDP per capita rank (out of 229 countries)?
187th
What is Chile’s HDI?
0.832
What is Nepal’s HDI?
0.602
What is Chile’s HDI rank (out of 191 countries)?
42nd
What is Nepal’s HDI rank (out of 191 countries)?
143rd
Why do people live in hazardous areas?
- May not be aware of risks of living close to plate margins
- Volcanoes mean there is fertile soil, rocks for building, rich mineral deposits and hot water
- Earthquake’s fault lines allow water supplies to reach the surface. Important in dry desert regions
- Effective monitoring of earthquakes and tsunamis mean that people receive warnings and have enough time to evacuate
- Better building design can withstand earthquakes
- Volcanic eruptions and earthquakes don’t happen often, so they’re not a threat to many lives
- People in poverty have other things to worry about (e.g., food, money, security and family)
- Plate margins may often coincide with very favourable areas for settlement, such as coastal areas where ports have developed
What are the four main management strategies for reducing the risk from tectonic hazards?
- Monitoring
- Prediction
- Planning
- Protection
What is monitoring?
Using scientific equipment to detect warning signs of events such as a volcanic eruption
What is prediction?
Using historic evidence and monitoring, scientists can make predictions about when and where a tectonic hazard can happen
What is protection?
Designing building that can withstand tectonic hazards
What is planning?
Identifying and avoiding places most at risk
How are volcanoes monitored?
- Remote sensing: satellites detect heat and changes to the volcano’s shape
- Seismicity: seismographs record earthquakes
- Ground deformation: changes to the shape of the volcano are measured using laser beams
- Geophysical measurements: detect changes in gravity as magma rises to the surface
- Gas - instruments detect gases released as magma rises
- Hydrology: measurements of gases dissolved in water
How are earthquakes monitored?
Cannot be monitored, as they occur with little or no warning
How are volcanoes predicted?
Based on scientific monitoring
How are earthquakes predicted?
Impossible to accurately predict earthquakes, due to the lack of clear warning signs, however scientists due study historical records, and know where earthquakes will happen soon
How do people protect themselves from volcanoes?
Earth embankments or explosives to divert lava flows away from property. This has been done on the slopes of Mount Etna in Italy
How do people protect themselves from earthquakes?
- Concrete columns strengthened by steel frames
- Tsunami walls
- Shock absorbers, to absorb ground shaking
- Rolling weights on roofs to counteract shock waves
- Automatic shutters to stop broken glass from falling
- Open areas for easy evacuation
How do people plan for a volcano?
Hazard maps
How do people plan for an earthquake?
Maps
