Tectonic Hazards

Question 1

What is the theory of plate tectonics?

Answer 1

The earth’s lithosphere (crust and upper mantle) is broken into several slabs known as tectonic plates, which can either be oceanic or continental, which float on the mantle and move very slowly due to convection currents in the mantle generated by radioactive decay

Question 2

Describe the earth’s structure

Answer 2

Picture

Question 3

What is a plate margin?

Answer 3

A long, narrow belt, which is the boundary between two tectonic plates (where they meet), which are either moving apart from (constructive), moving alongside (Conservative) or moving towards one another (destructive).

Question 4

Describe the global distribution of volcanoes and earthquakes

Answer 4

Generally found along plate boundaries, e.g. the Pacific Ring of Fire

Volcanoes may also be found at hotspots, which are far from plate boundaries, but where the mantle is simply very hot, e.g. Hawaii (far from the edge of the Pacific Plate)

Question 5

Where are plate boundaries generally found?

Answer 5

Along coastlines, e.g. West North and South American coastlines, south and East Asian coastlines

Question 6

What is a hotspot?

Answer 6

An area far from the edge of a plate boundary where the mantle is very hot. Volcanoes may occur here.

Question 7

Give an example of a constructive plate boundary

Answer 7

Eurasian and North American plates

Question 8

Give an example of a destructive plate boundary

Answer 8

Nazca and South American plates (oceanic and continental)

Question 8

Give an example of a conservative plate boundary

Are the plates moving in different directions, or the same direction at different speeds?

Answer 8

Pacific and North American Plate (San Andreas Fault Line)

Moving in the same direction at different speeds

Question 10

Why do Earthquakes occur at destructive plate boundaries?

Answer 10

Tectonic plates move towards each other at a destructive boundary due to converging convection currents in the mantle.

If the plates are both continental, the collision of plates and crumpling and folding of the crust will cause tension, release energy as shock waves.

If one plate is oceanic and one is continental, when the oceanic is subducted under the continental (due to being less dense), it may become stuck, creating tension due to friction and eventually causing it to fracture, sending out shock waves.

Question 11

Why do Earthquakes occur at constructive plate boundaries?

Answer 11

At constructive plate boundaries, the plates are moving away from each other due to diverging convection currents in the mantle below. As the plate moves, there is tension which builds up along cracks in the plates which may cause them to fracture and send out shock waves.

New plate material may also fracture and send out shock waves as it moves.

Question 12

Why do earthquakes occur at Conservative boundaries?

Answer 12

Plates may become stuck when moving past each other, causing tension to build up, which may cause them to fracture and send out shockwaves

Question 12

Why do volcanoes form at destructive plate boundaries?

Answer 12

When oceanic plates move down into the magma, they are melted and destroyed, forming a pressurised pool of magma.
Since the magma is less dense than the mantle above, it rises, and due to the pressure, rises through cracks in the crust known as vents.
The magma erupts onto the surface as lava at high pressure, forming a linear belt of composite volcanoes

Question 13

Primary Effects of Earthquakes

Answer 13

• buildings and bridges collapse, and homes are destroyed
• people are injured or killed by collapsed buildings and falling debris

– roads, railways, ports and airports are damaged, e.g. roads can buckle and crack

– electricity cables, gas, water pipes and communications networks are damaged, cutting off supplies

Question 14

Why do volcanoes form at constructive plate boundaries?

Answer 14

Magma rises up to fill the gap created by the plates moving apart, and erupts nonviolently onto surface as non-viscous lava, forming shield volcanoes

Question 16

Secondary Effects of Earthquakes

Answer 16

Earthquakes can trigger landslides and tsunamis- please destroy more buildings and cause more injuries and deaths

Leaking gas can be ignited, starting fires

People left homeless and could die, e.g. from cold

There is a shortage of clean water and lack of proper sanitation – this makes it easier for waterborne diseases such as cholera spread

Due to blocked or destroyed roads, aid and emergency vehicles can’t get through, and trade is difficult

Businesses are damaged or destroyed, causing unemployment and lost income, and tourists can be put off visiting the area

Repairs and reconstruction can be very expensive, so can weaken a country‘s economy

Question 16

Do volcanoes form at conservative plate boundaries?

Answer 16

No

Question 18

Immediate Responses to Earthquakes

Answer 18

Rescue people trapped by collapsed buildings, and treat injured people

Recover dead bodies to prevent spread of disease

Put out fires

Set up temporary shelters for people whose homes have been damaged or destroyed

Provide temporary supplies of water, food, electricity, gas and communication systems if regular supplies have been damaged

Foreign governments or charities may send aid workers, supplies, equipment or financial donations the areas affected

Tech companies may set up disaster response tools, allowing damage to be recorded and allowing people to confirm their safety, e.g. Google Crisis Response™️ service

Question 19

Long-term Responses To Earthquakes

Answer 19

Rehouse people who lost their homes

Repair and rebuild damaged buildings, roads, railways and bridges

Reconnect broken electricity, water, gas and communications connections

If necessary, improve building regulations so that buildings are more resistant to damage from earthquakes

Set up initiatives to help economic recovery, e.g. promoting tourism

Question 20

What is the difference between a composite volcano and a shield volcano?

Answer 20

Composite Volcano in comparison to a shield volcano:

• Longer periods between eruptions
• More violent eruptions
• Alternate layers of ash and lava (whereas shield is just lava)
• Steep sides - lava doesn’t flow far before solidification
• Acidic lava - v. viscous
• Found at destructive plate margins (whereas shield are found at constructive)

Question 21

Primary Effects of Volcanic Eruptions

Answer 21

Buildings and roads are destroyed by lava flows and pyroclastic flows. Buildings may also collapse if enough ash falls on them

People and animals are injured and killed by pyroclastic flows, lava flows and falling rocks

Crops are damaged and water supplies are contaminated when ash falls on them

People, animals and plants are suffocated by volcanic gases

Question 22

Secondary Effects of Volcanic Eruptions

Answer 22

Mudflows (lahars) form when volcanic material mixes with water, e.g. from heavy rainfall or snowmelt. Mudflows and landslides cause more death, destruction and injury

Flooding can be caused by hot rocks, ash and gas melting ice and snow on the volcano. Rock and ash clog up reviews and downs, making flooding worse

Transport networks are blocked or destroyed so aid and emergency vehicles can’t get through, and trade is difficult

People left homeless. Damaged or destroyed businesses can cause unemployment and loss of income

Tourism can be disrupted straight after an eruption – but often it can be increased afterwards with tourists interested in seeing volcanoes

Ash makes fields more fertile once broken down

Recovering after eruption can take a very long time and cost a huge amount of money, which can weaken the country’s economy

Question 23

Immediate Responses to Volcanic Eruptions

Answer 23

Evacuate people before the eruption, if it was predicted, or evacuate as soon as possible after the eruption starts

Provide food, drink and shelter for the evacuated people

Treat people injured by the eruption, e.g. from falling debris or ash inhalation

Rescue anyone cut off by damage to roads or buildings

Provide temporary supplies of electricity, gas and communication systems if regular supplies have been damaged

Foreign governments or charities may send aid workers, supplies, equipment or financial donations to the areas affected

Tech Companies may set up disaster response tools allowing damage to be recorded and people to confirm their safety, e.g. Google Crisis Response™️ service

Question 24

Long-Term Responses To Volcanic Eruptions

Answer 24

Repair and rebuild if possible, or resettle affected people elsewhere

Repair and reconnect infrastructure (roads, rail, power lines and communication networks etc.)

Improve, repair and update monitoring and evacuation plans

Boost economy if possible, e.g. by attracting tourists to see the volcano and its effects

Question 25

Primary Effects of the L’Aquila Earthquake

Answer 25

308 people died, mainly from collapsed buildings

1,500 people were injured

67,500 made homeless

10,000-15,000 buildings were damaged or destroyed, including:

• Churches, medieval buildings and monuments
• San Salvatore Hospital - patients had to be evacuated
• L’Aquila University

A bridge near the town of Fossa collapsed

A water pipe near the town of Paganica was broken

$11,434 million in damage

Question 26

Secondary Effects of the L’Aquila Earthquake

Answer 26

Aftershocks hampered rescue efforts and caused more damage, including landslides and rockfalls

The broken water pipe caused a landslide and mudflow

Electricity and phone disrupted, though most repaired within a day

Fires in collapsed buildings caused more damage

No. Students at L’Aquila Uni have gone down

Lack of housing = house prices and rents up

CBD cornered off = loss of income, business + trade

Question 27

Immediate Responses to the L’Aquila Earthquake

Answer 27

Camps set up for people made homeless = food, water, medical care - 40,000 tents given out

Hotels provided shelter for more than 10,000

Ambulances, fire engines & the army sent in to rescue survivors, and Italian Red Cross sent in within an hour

Silvio Berlusconi (Then prime minister) offered some of his homes as shelters

Cranes & diggers used to remove rubble

British Red Cross raised £171,000 in support

Free mobile phones and SIM cards provided to people who had lost homes

EU granted $559.2 million for rebuilding

Money provided by government to pay rent, and gas and electricity bills were suspended

Question 28

Long-Term responses to the L’Aquila Earthquake

Answer 28

New settlements built to accommodate over 20,000 residents who used to live in the damaged city centre

Most of the city centre is being rebuilt, but there have been criticisms over delays

An investigation was set up into why modern buildings weren’t built to withstand earthquakes, and ensured that new ones were

No taxes in 2010

No university fees at L’Aquila University for three years