3. Natural Hazards

Question 1

What is a natural event

Answer 1

Something happening in the physical environment, such as a storm, volcanic eruption or earthquake.

Question 2

What is a hazard

Answer 2

An event which threatens the well-being of PEOPLE and their property

Question 3

What is a natural hazard

Answer 3

A natural hazard is an extreme natural event that can cause loss of life, extreme damage to property and disrupt human activities.

Question 4

Give 3 examples of a geological hazard

Answer 4

• earthquake
• tsunami
• volcanic eruption

Question 5

Give 3 examples of a climatic hazard

Answer 5

• hurricane
• tornado
• blizzard

Question 6

Give 3 examples of a biological hazard

Answer 6

• fires (grassland/forest)
• plague/ insect infestation
• diseases

Question 7

Give 3 examples of a technological hazard

Answer 7

• nuclear explosion
• pollution
• accidental release of toxic chemicals

Question 8

What is a natural disaster

Answer 8

A disaster is the realisation of a hazard.

Question 9

What is a tropical cyclone

Answer 9

A tropical cyclone is a weather system of very low-pressure formed over tropical seas and involving strong winds and heavy rainfall (also known as a cyclone, hurricane or typhoon).

Question 10

What is the Saffir-Simpson Hurricane Wind Scale (measurement)

Answer 10

The Saffir-Simpson Hurricane Wind Scale is a 1 to 5 rating based on a hurricane’s sustained wind speed. This scale estimates potential property damage.

Question 11

What is the range in wind speed of the Saffir-Simpson Hurricane Wind Scale

Answer 11

74mph (category 1) - 157mph (category 5)

Question 12

Where are tropical cyclones distributed

Answer 12

Between roughly 5-20° north/south of the equator where water is deep and warm

Question 13

Where do we call a tropical cyclone a ‘hurricane’

Answer 13

Atlantic and Northeast Pacific - hurricane

Question 14

Where do we call a tropical cyclone a ‘typhoon’

Answer 14

Northwest Pacific

Question 15

Where do we call a tropical cyclone a ‘cyclone’

Answer 15

South Pacific and Indian Ocean

Question 16

Key characteristics of a tropical cyclone

Answer 16

• Humid, warm, unstable air, low pressure
• A constant supply of energy (the warm water)
• Warm water above 27*
• A circulatory motion of air and small changes in wind speed and direction

Question 17

Is a tropical cyclone a weather system of low or high pressure

Answer 17

LOW PRESSURE (A low pressure system has lower pressure at its centre than the surrounding areas. Winds blow towards the low pressure, and the air rises in the atmosphere where they meet. As the air rises, the water vapour within it condenses, forming clouds and often precipitation.

Question 18

Weather conditions when the hurricane approaches

Answer 18

• temp and pressure begin to fall

- (winds from the north-west)

Question 19

Weather conditions for the first ‘wall’ of the storm

Answer 19

• pressure falls rapidly

- cumulonimbus clouds with thunder and torrential rain

Question 20

Weather conditions in the eye of the hurricane

Answer 20

• period of calm, sun makes a brief appearance

- pressure very low

Question 21

Weather conditions for the second ‘wall’ of the storm

Answer 21

• hurricane winds and torrential rain

- (south-east winds, temp drops, pressure rises)

Question 22

Weather conditions towards the end of the hurricane

Answer 22

• pressure and temperature rise

- rain and wind decrease

Question 23

What is the Coriolis force

Answer 23

• scientist’s explanation for why a moving object (tropical cyclone) will veer towards the right in the Northern Hemisphere and the south in the Southern Hemisphere
• due to the earth’s rotation on its axis (rotates faster at the equator than at poles)

Question 24

What is wind shear

Answer 24

Wind shear is the change in speed or direction of wind over a relatively short distance or time period. Hurricanes need small changes in wind speed and direction, but if the wind shear force is too strong, then hurricanes may dissipate because the storm is pushed or spread over a larger area

Question 25

Specify what is meant by ‘unstable air pressure’

Answer 25

Where areas of high pressure and low pressure meet

Question 26

State and explain 3 physical effects of a tropical cyclone

Answer 26

1. flooding - crop damage - food shortage - starvation
2. heavy rain causing freshwater flooding - spread of disease due to unhygienic conditions - drinking contaminated water - illness + death
3. strong winds - destroy infrastructure/ housing - homelessness, loss of income - social disorder/conflict

Question 27

Give one short term impact of a tropical cyclone

Answer 27

Strong winds - destroy infrastructure/ housing - leaving people homeless

Question 28

Give one long term impact of a tropical cyclone

Answer 28

-

Question 29

What is a volcanic eruption

Answer 29

Volcanic eruptions happen when lava and gas are discharged from a volcanic vent.

Question 30

What is lahar

Answer 30

lahar is a mudflow caused by water and debris mixing during a volcanic eruption. It is an Indonesian term that describes a mixture of water and rock fragments.
It makes a hot, muddy flow that usually flows down existing river valleys, collecting debris and causing severe destruction to property.

Question 31

What is pyroclastic flow

Answer 31

A pyroclastic flow is a hot moving current of ash and gas. It is the most dangerous characteristic of a volcanic eruption.

Question 32

What dangerous gasses are released after a volcanic eruption

Answer 32

• sulphur
• cyanide
• carbon dioxide

Question 33

Why are ash clouds dangerous

Answer 33

• Ash causes damage by blanketing everything e.g. crops and roads
• Roofs of buildings often collapse under the weight of deposited ash

Question 34

What is a destructive/convergent plate boundary

Answer 34

This occurs when oceanic and continental plates move together. The oceanic plate is forced under the lighter continental plate. Friction causes melting of the oceanic plate and may trigger earthquakes. Magma rises up through cracks and erupts onto the surface.

Question 35

What is a constructive/divergent plate boundary

Answer 35

A constructive plate boundary occurs when plates move apart. Volcanoes are formed as magma wells up to fill the gap, and eventually new crust is formed.

Question 36

What are hotspots

Answer 36

• Some volcanoes do not occur on plate boundaries, so they can be formed over hotspots.
• These are fixed points in the mantle that generate intense heat (in a mantle plume). Small, long lasting, exceptionally hot areas of magma exist under the Earth’s surface which in turn sustains long-lasting volcanic activity.
  At areas where the pressure is greater in the mantle, magma erupts through the crust as when the plume reaches the crust it causes the crust to dome (and crack).
  Volcanoes are created if the magma rises above the ocean surface.

Question 37

What is a collision plate boundary

Answer 37

Collision zones form when two continental plates collide. Neither plate is forced under the other, and so both are forced up and form fold mountains.

Question 38

What is a conservative plate boundary

Answer 38

A conservative plate boundary, sometimes called a transform plate margin, occurs where plates slide past each other in opposite directions, or in the same direction but at different speeds.

Friction is eventually overcome and the plates slip past in a sudden movement. The shockwaves created produce an earthquake.