3.1.1.2 Tectonic hazards

Question 1

Name and describe the 4 layers that make up the Earth

Answer 1

1. Core of Earth is a ball of solid (inner) and liquid (outer) iron and nickel
2. Around core is mantle → semi-molten rock that moves very slowly
3. Outer layer of Earth is crust

Question 2

Name and describe the 2 types of crust

Answer 2

Oceanic crust - Thinner (5-10km) and more dense

Continental crust - Thicker (30-50km) and less dense

Question 3

Why do tectonic plates move?

Answer 3

Plates are moving because of convection currents in mantle underneath crust

Question 4

What are plate margins/plate boundaries?

Answer 4

Places where plates met

Question 5

Name the 3 types of plate margins

Answer 5

Destructive Margins
Constructive Margins
Conservative Margins

Question 6

What are destructive margins and give an example where they can be found?

Answer 6

Where two plates are moving towards each other e.g along west coast of South America

Question 7

Where and how are ocean trenches formed?

Answer 7

Formed at a destructive margin, where an oceanic plate meets a continental plate, denser oceanic plate is formed down into mantle and destroyed = often creates ocean trenches

Question 8

What are ocean trenches?

Answer 8

Very deep sections of ocean floor where oceanic plate goes down

Question 9

Where and how are mountain ranges formed?

Answer 9

Formed at a destructive margin, where two continental plates meet, plates collide and ground is folded and forced upwards to create mountain ranges

Question 10

What are constructive margins and give an example where they can be found

Answer 10

Where two plates move away from each other e.g. At mid-Atlantic ridge

Question 11

Where and how is new crust formed?

Answer 11

At constructive margin, where two plates move away from each = magma (molten rock) rises from mantle to fill gap and cools, creating new crust

Question 12

What are conservative margins and give an example where they can be found?

Answer 12

Where two plates are moving sideways past each other, or are moving in same direction but at different speeds e.g. Along west coasts of USA

Question 13

Is crust destroyed or created at conservative margins?

Answer 13

No

Question 14

Where are volcanoes formed?

Answer 14

Volcanoes are found at destructive and constructive plate margins

Question 15

How does a volcano form at a destructive margin?

Answer 15

At destructive plate margins, oceanic plate goes under continental plate because it’s more dense.
Oceanic plate moves down into mantle where it’s melted and destroyed
A pool of magma forms.
Magma rises through cracks in crust called vents.
Magma erupts onto surface (called lava) forming volcano.

Question 16

How does a volcano form at a constructive margin?

Answer 16

At constructive margins magma rises up into gap created by plates moving apart = forming a volcano

Question 17

Where else can a volcano form and give an example?

Answer 17

Volcanoes also form over parts of mantle that are really hot called hotspots e.g. Hawaii

Question 18

What does a volcano emit when it erupts?

Answer 18

Lava and gases

Question 19

What happens when a volcano emits a lot of ash? (name 3 things)

Answer 19

The ash can cover land, block out the sun and form pyroclastic flows

Question 20

What are pyroclastic flows?

Answer 20

Super-heated currents of gas, ash and rock

Question 21

Where do earthquakes occur?

Answer 21

At all three plate margins

Question 22

How are earthquakes caused?

Answer 22

Earthquakes are caused by tension that builds up at all 3 types of plate margin
Plates eventually jerk past each other, sending out shock
waves (vibrations - earthquakes)
Shock waves spread out from focus (point in earth
where earthquake starts)

Question 23

Describe how tension is built up at each plate margin

Answer 23

Destructive - Tension builds up when one plate gets stuck as it’s moving down past other into mantle
Constructive - Tension builds along cracks within plates as they move away from each other
Conservative - Tension builds up when plates that are
grinding past each other get stuck

Question 24

Where are the shock waves the strongest and most damaging?

Answer 24

Near focus, waves are stronger and cause more damage

Question 25

What is an epicentre?

Answer 25

Epicentre is point on the Earth’s surface straight above focus

Question 26

What are the primary effects of an earthquake (name 4)?

Answer 26

1. Buildings + bridges collapse/homes are destroyed
2. People are injured/killed by collapsed building + falling debris
3. Road, railways, ports and airports are damaged
4. Electricity cables, gas and water pipes and communications networks = damaged, cutting off supplies

Question 27

What are the secondary effects of an earthquake (name 4)?

Answer 27

1. Earthquakes = landslides and tsunamis = destroy more buildings + = injuries/deaths
2. Leaking gas - ignited = fires
3. People are left homeless + could die
4. Shortage of clean water + lack of proper sanitation = diseases spread
5. Blocked/destroyed roads = aid + emergency vehicles can’t get through + trade is difficult
6. Businesses are damaged/destroyed = unemployment + lost income + tourism decreases
7. Repairs + reconstruction = expensive = weaken country’s economy

Question 28

What are the immediate responses of an earthquake (name 4)?

Answer 28

1. Rescue people trapped + treat injured people
2. Recover dead bodies to prevent spread of disease
3. Put out fires
4. Set up temporary shelters (for homeless)
5. Provide temporary supplies (water, food, electricity, gas) + communications system
6. Foreign governments/charities send aid workers, supplies, equipment or financial donations
7. Tech companies set up disaster response tools = damage can be recorded + people confirm their safety

Question 29

What are the long-term responses of an earthquake (name 4)?

Answer 29

1. Re-house people
2. Repair/rebuild damaged infrastructure
3. Reconnect broken electricity, water, gas + communications connections
4. Improve building regulations (buildings more resistant to earthquakes)
5. Set up initiatives to help economic recovery

Question 30

What are the primary effects of an volcano eruption (name 4)?

Answer 30

1. Buildings and roads = destroyed by lava flows and pyroclastic flow
2. People, animals are injured/killed by pyroclastic flows, lava flows and falling rocks
3. Crops = damaged + water supplies = contaminated due to ash
4. People, animals and plants = suffocated by volcanic gases

Question 31

What are the secondary effects of an volcano eruption (name 4)?

Answer 31

1. Mudflows (lahars) more destruction, death, injury
2. Flooding caused by hot rock, ash and gas melting ice and snow on volcano
3. Transport networks = blocked/destroyed = aid and emergency vehicles can’t get through = trade is difficult
4. Ash makes fields more fertile once it’s broken down
5. Tourism disrupted straight after eruption but cam increase afterwards
6. Damaged/destroyed businesses = unemployment and loss of income
7. Recovering = expensive, weakening country’s economy

Question 32

What are the immediate responses of an volcano eruption (name 4)?

Answer 32

1. Evacuate people before eruption or evacuate ASAP after eruption starts
2. Provide food, drink and shelter for evacuated people
3. Treat people injured
4. Rescue anyone cut off by damage to roads or bridges
5. Provide temporary supplies of electricity, gas and communications system
6. Foreign governments or charities may send aid workers, supplies, equipment or financial donations
7. Tech companies set up disaster response tools = damage cam be recorded + people confirm their safety

Question 33

What are the long-term responses of an volcano eruption (name 4)?

Answer 33

1. Repair/rebuild or resettle affected people
2. Repair and reconnect infrastructure
3. Improve, repair and update monitoring and evacuation plans
4. Boost economy (e.g. Attracting tourists to see volcano and its effects)

Question 34

Name 4 reasons why people live in areas at risk from tectonic hazards

Answer 34

• Always lived there, moving away = leaving friends and family
• Employed in area = would have to find new job
• Confident of support from their government after tectonic hazard
• Soil around volcano is fertile (full of minerals from
  volcanic ash and lava)
• Some think severe earthquakes/eruptions won’t happen again
• Lots of tourists visit volcanoes + people live around volcanoes to work in tourist industry

Question 35

What are main 4 management strategies for tectonic hazards

Answer 35

Monitoring
Prediction
Protection
Planning

Question 36

Name 2 examples of monitoring

Answer 36

1. Seismometers + lasers monitor earth movements = used in early warning systems to warn people before earthquake occurs
2. Scientists can monitor signs that come before volcanic eruption

Question 37

Name 2 examples of prediction

Answer 37

1. Earthquakes ≠ reliably predicted BUT can monitor movement of tectonic plates = can forecast which areas need to be prepared
2. Volcanic eruptions = predicted if volcano well-monitored
   Predicting area of eruption = gives people time to evacuate = reduces no. of injuries and deaths

Question 38

Name 3 examples of protection

Answer 38

1. Buildings designed to withstand earthquakes
2. Existing buildings + bridges can be strengthened (e.g. wrapping pillars in steel frames) = less likely to collapse
3. Automatic shut-off switches fitted = turn off gas + electricity supplies = prevent fires if earthquake detected by monitoring system

Question 39

Name 4 examples of planning

Answer 39

1. Future developments planned to avoid areas at risk from tectonic hazards
2. Emergency services can train and prepare for disasters = reduce no. of people killed
3. People can be educated = know what to do if volcano erupts/earthquake occurs
4. Government can plan evacuation routes = get people out of dangerous areas quickly and safely = reduces no. of people killed or injured
5. Emergency supplies can be stockpiled

Question 40

What are lahars?

Answer 40

Aka mudflows - when volcanic material mixes with water e.g. From heavy rainfall or snow melt