Tectonic Hazards

Question 1

Earthquakes

Answer 1

a sudden or violent movement withing the Earth’s crust followed by a series of shocks

Most occur at the margins of slowly moving tectonic plates. Friction and sticking between the plates creates enormous pressures and stresses which build up to breaking point. However, activities such as mining or oil extraction can cause them.

Question 2

Volcanoes

Answer 2

they are large, and often cone shaped landforms, formed over long periods by eruptions. They are fed with molten rock (magma) from deep within the earth’s mantle. Like earthquakes, most occur in belts along plate margins (e.g. the ‘pacific ring of fire’ and the mid-Atlantic ridge). But some occur at hot spots where the crust is thin and magma breaks through.

Question 3

Describe the different types of crusts

Answer 3

Oceanic crust - dense, thin

Continental crust - less dense, thicker

Question 4

Overview on Plate margins

Answer 4

Plates move, driven by convection currents within the mantle and under gravity.

At constructive plate margins, plates separate, forming new crust, causing massive volcanic eruptions.

At destructive plate margins, plates collide, causing subduction, earthquakes, volcanic eruptions and fold mountains.

At conservative plate margins, plates slide by each other, causing earthquakes.

Question 5

Constructive Margins

Answer 5

The convection currents move the plates apart. This allows the magma to force its way up. Once it hits the sea, it cools and solidifies forming new land which can be ocean ridges such as the Mid Atlantic ridge in Iceland, cone volcanoes or cause earthquakes.

e.g. Iceland

Question 6

Destructive Margins

Answer 6

two plates move towards each other due to convetion currents pulling and dragging the plates. The plates are jammed together causing friction. The rocks are constantly against together and the pressure builds up over a large period of time. Once the pressure overcomes the friction, the thin oceanic plate is sub-ducted beneath the thick continental plate. Friction between the plates causes strong earthquakes . The sinking oceanic plate creates sticky, gas rich magma. This results in steep-sided composite volcanoes which erupt violently as the melting crust feeds it.

e.g. Nazca plate sub ducting underneath the South American plate

Question 7

Conservative Margins

Answer 7

The convection currents move two places in opposite directions or different speeds.
Friction builds up between these two plates and they suddenly move apart. This causes an earthquake.

E.g. San Andreas Fault
The faster moving Pacific Plate is sliding in the same direction next to the slower moving North American Plate.

Question 8

Collision boundary

Answer 8

Where two continental plates meet there is no subduction, so there is no magma to form volcanoes. The crust crumples and lifts to form fold mountains (e.g. the Himalayas). Powerful earthquakes can be triggered.

Question 9

Geographical location of Chile

Answer 9

• SW of South America
• west of Chile is the Pacific Ocean
• East is the Andes and Argentina
• Borders with Peru and Bolivia in the north

Question 10

Contextual information about Chile

Answer 10

Population: 16.7 million
Urban Population: 89%
GDP: 38th of 193 countries
HDI: 41st out of 187 countries

Question 11

Overview of Chile 2010

Answer 11

Magnitude = 8.8
Feb 2010
Close to the Coast therefore cause Tsunami

Question 12

Primary Effects of Chile 2010 earthquake

Answer 12

• 500+ died
• 12,000 injured
• Cost estimated US $30 billion
• Widespread power cuts
• 220 000 homes, 4500 schools, 53 ports, 56 hospitals and other public buildings destroyed.

Question 13

Secondary Effects of Chile 2010

Answer 13

• Tsunami
• 1500km of roads damaged, mainly by landslides – remote communities cut off for many days.
• A fire at a Santiago chemical plant – area had to be evacuated

Question 14

Immediate Responses of Chile 2010

Answer 14

• Swift and effective response by emergency services
• Key roads repaired within 24h
• Water and power restored to 90% of homes in 10 days
• US$60 million national appeal built 30 000 emergency wooden shelters.

Question 15

Long Term Response of Chile 2010

Answer 15

• Strong economy reduced the need for foreign aid, based on copper exports.
• Government reconstruction plan to help 200 000 households
• Full recovery estimated took 4 years.

Question 16

Geographical Information of Nepal

Answer 16

• in Asia specifically in the Himalayas
• Bordering India and China
• Land locked
• On a destructive plate margin. (Indian plate sub ducting the Eurasian plate)

Question 17

Contextual Information about Nepal

Answer 17

Population: 29million in 2010
GDP: 109/193
HDI: 145/187

Question 18

Overview on Nepal 2015 earthquake

Answer 18

7.8 on Richter scale. Shallow (only 15km below ground), epicentre was 80km north-west of Kathmandu, Nepal’s capital.

Question 19

Primary Effects of Nepal 2015

Answer 19

• 9000 people dies and 20 000 injured, over 8 million people affected (1/3 of population) affected.
• 3 million left homeless.
• 50% of shops destroyed, affecting people’s livelihoods and food supplies.
• Cost estimated at over US$5 billion.

Question 20

Secondary Effects of Nepal 2015

Answer 20

• Landslides and avalanches triggered, they blocked roads and hampered relief efforts.
• Avalanches killed at least 19 people on mount Everest
• 250 people missing after avalanche in Langtang region.

Question 21

Immediate Responses in Nepal 2015

Answer 21

• Aid included helicopters to reach cut of areas
• Half a million tents needed to provide shelter for the homeless.
• Financial aid pledged from many countries including India
• 300 000 people migrated from Kathmandu
• Local people played a central role in the search and rescue of people
• emergency services were disorganised at times

Question 22

Long term Responses in Nepal 2015

Answer 22

• Roads repaired, landslides cleared and flood lakes drained.
• In June 2015 Nepal hosted an international conference to discuss reconstruction.
• Tourism to be boosted, by July 2015 some heritage sited reopened.
• in August 2015 Everest reopened for climbers after repairing the Everest Base camp and trekking routes

Question 23

Why do people live with tectonic risk

Answer 23

E.g. Iceland

• cheap electricity + heating
• hydroelectric power
• Geothermal energy generates 25% of Iceland’s electricity
• Industries: Tourism and Fishing
• Large earthquakes and volcanic eruptions don’t occur that often, so people aren’t so scared.
• Better building design makes people feel less at risk
• More effective monitoring can help evacuations

Others:

• Volcanoes bring benefits: fertile soil, rocks for building, rich mineral deposits and hot water.
• Plate margins often coincide with favourable areas for settlement, such as coastal areas where there are ports.

Question 24

Managing Earthquakes Strategies: Monitoring

Answer 24

Scientists are yet to find reliable ways to monitor and then predict them. However, they can try with; laser beams, gas, animal behaviour, seismometer, water pressure, ground deformation and minor prior tremors.

Question 25

Managing Earthquakes Strategies: Prediction

Answer 25

impossible to make accurate predictions but studying historical records can give scientist ideas about areas most at risk.

Question 26

Managing Earthquakes Strategies: Protection

Answer 26

1. Rolling weights on roof to counteract shock waves
2. Walls reinforced with steel and concrete to reduce movement
3. Automatic shutters come down over windows to prevent glass falling
4. Reinforced Foundations and Shock absorbers to absorb ground shaking
5. Open areas for evacuation

Question 27

Managing Earthquakes Strategies: Planning

Answer 27

– maps can be produced to show the effects so areas of high risk can be identified and high-value land uses can then be protected in those areas.
- earthquake drills in school

Question 28

Managing Volcanoes Strategies: Monitoring

Answer 28

Modern hi-tech equipment is used to monitor volcanoes and give warning signs when necessary. This is done with; remote sensing = satellites that detect heat and changes to volcano’s shape
seismicity = seismography record earthquakes
ground deformation = changes to the shape of the volcano are measure using laser beams
Gas = instruments detect gases released as magma rises
hydrology = measurements of gses dissolved in H2O

Question 29

Managing Volcanoes Strategies: Prediction

Answer 29

Based on scientific monitoring

Question 30

Managing Volcanoes Strategies: Protection

Answer 30

their sheer power means that not much can be done, but earth embankments can help divert lava flow.

Question 31

Managing Volcanoes Strategies: Planning

Answer 31

Hazard maps have been created for the most dangerous volcanoes, which can be used in planning to restrict certain land uses to identify which areas need to be evacuated when an eruption is about to happen.
- drills can also take place

Question 32

Different types of Management Strategies

Answer 32

Monitoring = using scientific equipment to detect warning signs of events
Prediction = using historical evidence and monitoring, scientists can make predictions
Protection = designing buildings that will withstand tectonic hazards.
Planning = identifying and avoiding places most at risk