Managing Natural Hazards

Question 1

Structure of Earth

Answer 1

1. Crust
2. Upper Mantle
3. Mantle
4. Outer Core
5. Inner Core

Question 2

Describe the Crust

Answer 2

1. Solid
2. Oceanic Crust- thinner & denser (under oceans)
3. Continental Crust- thicker & less dense (under mountain chains)
4. Fractured into large tectonic plates that are slow and in constant motion

Question 3

Describe the Mantle

Answer 3

1. 84% of Earth’s volume
2. Upper Mantle below the crust & is mostly solid- moves like melted plastic around plate boundaries
3. Lower mantle is hotter & denser
4. Temp & Pressure increases with depth

Question 4

Define plate boundaries

Answer 4

Edges of tectonic plates

Question 5

What is the lithosphere?

Answer 5

Topmost part of the upper mantle & crust

Question 6

Explain the movement of tectonic plates above

Answer 6

Semi-liquid rock in the upper mantle is heated by the core & lower mantle
It rises towards the lithosphere
Descends into giant convection currents which drive the movement

Question 7

Describe the Core

Answer 7

1. Extreme temp derived from the radioactive decay of material from 4.5 billion years ago
2. Layer of liquid iron above

Question 8

Explain Earth’s magnetic field

Answer 8

The layer of cool iron allows the iron and nickel to move in convection currents
This movement creates the field

Question 9

4 main types of plate boundary

Answer 9

1. Constructive/ Divergent
2. Destructive/ Convergent
3. Collision
4. Conservative/ Transform

Question 10

Define Constructive/ divergent plate boundaries

Answer 10

When 2 PLATES ARE MOVING AWAY and a new crust is formed in submarine volcanoes when magma rises

Question 11

Define Destructive/ Convergent plate boundaries

Answer 11

When dense OCEAN CRUST CONVERGES WITH CONTINENTAL crust, it is pushed down into the upper mantle at subduction zones

As it descends it melts, causing magma to rise and form volcanoes & ocean trenches

Question 12

Define collision plate boundaries

Answer 12

Continental crust (same density) collides with others and plates are pushed upwards forming fold mountains

Question 13

Define conservative/ transform plate boundaries

Answer 13

Plates do not slide, instead friction is built up and released using earthquakes

Question 14

How do earthquakes form?

Answer 14

Tectonic plates are stuck due to friction
Pressure builds over time
Releases and huge shock waves of energy travel outwards along the surface, causing things to shake

Question 15

Loss of life depends on a range of factors

Answer 15

1. Depth of earthquake focus
2. Geology of area
3. Size & Magnitude
4. Vulnerability of population

Question 16

Measurements of intensity

Answer 16

1. Mercalli intensity (1-12)
2. Richter magnitude (1-8+)

Question 17

Impacts of earthquakes

Answer 17

1. Loss of life
2. Damage to buildings
3. Destroyed infrastructure
4. Water-borne diseases (cholera)
5. Landslides
6. Tsunamis

Question 18

How do volcanoes form?

Answer 18

They form at constructive and destructive plate boundaries as well as magma hotspots

Question 19

Strength of eruption measure

Answer 19

Volcanic Explosivity Index (VEI)

Question 20

Impacts from eruptions

Answer 20

1. Lava flows
2. Gas clouds (CO2 & nitrous oxide)
3. Volcanic bombs
4. Loss of life
5. Loss of farmland and habitats

Question 21

Reduce earthquake risk beforehand

Answer 21

1. Large scale earthquake drills
2. Retrofitting old buildings
3. Educating population
4. Local govts have detailed emergency management plan
5. Mapping faults

Question 22

Reducing earthquake risk during the event

Answer 22

1. Send signals/ warnings to people
2. Seismometers send signals to medical, fire, rescue stations

Question 23

Reducing earthquake risk after event

Answer 23

1. Search and rescue operation
2. Meeting immediate needs of survivors
3. Clean up, demolish, repair, planning
4. Rebuild, reconstruct, replace

Question 24

Reducing volcanic eruption risk before the event

Answer 24

1. Evacuation plans
2. Gas levels can be monitored
3. Hazard risk maps
4. Volcano shelters
5. Education

Question 25

Reducing volcanic eruption risk during the event

Answer 25

1. Evacuation
2. Ongoing monitoring for lahar
3. Local air traffic will be diverted
4. Resettlement

Question 26

Reducing volcanic eruption risk after the event

Answer 26

1. Rescue from damaged buildings
2. Clear the ash-fall
3. Permanent abandonment of some settlement

Question 27

Why do volcanoes erupt?

Answer 27

Magma collects in magma chamber​
Pressure increases causing fractures​
Magma is less dense than surrounding solid rock so rises​
Erupts on the surface through a volcano as lava, ash and gas​

Question 28

Define epicentre

Answer 28

Point on the Earth’s surface directly above where an earthquake occurs

Question 29

Ways volcanoes are described

Answer 29

1. Still active and erupting frequently
2. Dormant (temporarily inactive but not extinct)
3. Extinct

Question 30

Difference between types of volcanos

Answer 30

1. Dome :
   Thicker, more vicious lava
2. Fissure:
   Lava out of a thin, long vent
3. Shield:
   Runny lava

Question 31

Stratovolcanos

Answer 31

Lava dome with ash
Contain gases that increase explosivity

Question 32

Components of an earthquake-proof building

Answer 32

1. Identification no. for helicopters
2. Open areas for evacuation
3. Weights on roof to counteract shock waves

Question 33

Define lahar

Answer 33

Mix of rainwater and ejected volcanic materials

Question 34

Opportunities from Volcano eruptions

Answer 34

1. Calderas form- agriculture employment
2. Volcanic ash is highly fertile for soil
3. Tourist treks & bike rides
4. Fishing, water sports, irrigation, drinking source
5. Minerals that are mined- volcanic ash
6. Produce electricity (geothermal power)
7. Volcanic rock statues