challenge of natural hazards

Question 1

What is a ‘natural hazard’?

Answer 1

A
A natural event (for example earthquake, volcanic eruption, tropical storm, flood) that threatens people or has the potential to cause damage, destruction and death

Question 2

what are the risk

Answer 2

hazard risk is the chance or probability of being affected by a natural event

Question 3

List some examples of natural hazards (and their category if you can)

Answer 3

A
Tectonic hazards (e.g. earthquake, tsunami, volcanic eruption)
Atmospheric hazards (e.g. hurricanes)
Geomorphological hazards (e.g flooding)
Biological hazards (e.g. forest fires)

Question 4

What factors affect hazard risk?

Answer 4

Poverty - poorer places will struggle to adequately prepare for a hazard or be able to respond.
Magnitude - the severity of the hazard will make the impacts worse
Population density - areas that have high populations will experience more destruction.
Education - how educated the population are to react and prepare for the hazard

Question 5

Describe the structure of the earth starting from the outermost layer?

Answer 5

OUTERMOST: 1. Crust - the outermost layer of the Earth, broken into tectonic plates.
2. Mantle - semi-molten part of the Earth.
3. Outer core - liquid iron and nickel

CENTRE: 4. Inner core - solid iron and nickel

Question 6

What causes the plates to move?

Answer 6

A
Convection currents in the mantle

Question 7

What are convection currents?

Answer 7

Circulating movements of magma in the mantle caused by the heat of the core

Question 8

Describe the global distribution of earthquakes?

Answer 8

Earthquakes occur in lines which coincide with plate margins. There are many along the western coast of North and South America.

Question 9

Describe the global distribution of volcanic eruptions.

Answer 9

Volcanoes are found both on land and in the sea. They tend to be found along plate margins. Some volcanoes are found in the centre of plates. These are known as hot spots. There is a large band of volcanoes around the Pacific Ocean known as the Ring of Fire.

Question 10

What is oceanic crust?

Answer 10

The part of the Earth’s crust which is below the oceans.

Question 11

What is continental crust?

Answer 11

The part of the Earth’s crust that makes the continents

Question 12

What is the difference between oceanic and continental crust?

Answer 12

Oceanic crust is thinner (5-10km thick) and more dense than continental crust.
Oceanic crust is recycled at destructive margins as it subducts under the continental crust.
Continental crust is thicker (20-200km thick) and is less dense than oceanic crust.
Continental crust cannot be destroyed.

Question 13

conservative plate margin?

Answer 13

A plate margin where the tectonic plates are sliding past each other

Question 14

constructive plate margin?

Answer 14

A plate margin where the tectonic plates are moving apart

Question 15

destructive plate margin?

Answer 15

A plate margin where an oceanic and a continental plate collide.

Question 16

tectonic hazards?

Answer 16

Threats posed by earthquakes, volcanoes etc

Question 17

What is subduction?

Answer 17

The transformation into magma of a denser tectonic plate as it dives under a less dense plate

Question 18

Define ‘epicentre’?

Answer 18

The point on the ground directly above the focus (centre) of the earthquake

Question 19

Define ‘focus’?

Answer 19

The point of origin of an earthquake

Question 20

Define ‘magnitude’?

Answer 20

The size of an earthquake

Question 21

What is an ocean trench?

Answer 21

A deep depression on the ocean floor formed at the subduction zones of destructive plate margins

Question 22

What are tectonic plates?

Answer 22

The large pieces of broken crust that cover the earth

Question 23

What is a plate margin?

Answer 23

The boundary between two tectonic plates

Question 24

What are primary effects?

Answer 24

The impacts of a natural disaster that happen immediately or soon after the event

Question 25

Define response?

Answer 25

The way in which people react to a situation eg. an earthquake

Question 26

What are secondary effects?

Answer 26

The after effects of a disaster eg. disease spreads or economic losses

Question 27

Define ‘tsunami’?

Answer 27

Huge waves caused by earthquakes under the sea

Question 28

List two characteristics of an oceanic crust

Answer 28

5-10 km thick
Dense
Destroyed at destructive plate margins
Forms constantly at constructive plate margins
Geologically young compared to continental crust

Question 29

List two characteristics of a continental crust

Answer 29

20-200km thick
Less dense (than oceanic)
Cannot be destroyed. New crust is not formed
It is geologically old 3-4 billion years old

Question 30

What is an earthquake?

Answer 30

Earthquakes are vibrations in the Earth’s crust that create shaking at the surface. They are highly unpredictable and often occur suddenly without warning, mainly on the plate margins

Question 31

Do earthquakes happen on all four plate boundaries?

Answer 31

yes

Question 32

Why do earthquakes happen?

Answer 32

Earthquakes occur because stresses build up between the plates as one plate passes another.
As the plates move past one another they don’t do so smoothly, rather, they snag and grind, allowing energy to build up.
When the plates eventually move again this energy is released as shock or seismic waves through the Earth’s crust.
The point at which the earthquake is occurring is called the focus.
The point above this on the surface of the earth is called the epicentre.

Question 33

List two characteristics of a composite volcano?

Answer 33

Made up of alternating layers of lava and ash (other volcanoes just consist of lava)
Found at destructive boundaries
Often has pyroclastic flows. A pyroclastic flow is a mixture of hot steam, ash, rock and dust
A pyroclastic flow can roll down the sides of a volcano at very high speeds and with temperatures of over 400°C

Question 34

List two characteristics of a shield volcano?

Answer 34

Shield volcanoes are usually found at constructive or tensional boundaries
They are low, with gently sloping sides
They are formed by eruptions of thin, runny lava
Eruptions tend to be frequent but relatively gentle

Question 35

Can we predict volcanic eruptions and earthquakes?

Answer 35

Volcanoes - Yes
Earthquakes - No

Question 36

List some reasons why people live in areas at risk from tectonic hazards?

Answer 36

Fertile farmland on volcanic soil (environmental)
Income from tourism (economic)
Lack of other alternatives (social)
Mining precious minerals (socio-economic)

Question 37

How do we measure the size of the earthquake?

Answer 37

Richter Scale - Measured from 1-9

Question 38

At which plate margin can earthquakes occur?

Answer 38

All plate margins (constructuve, destructive and conservative)

Question 39

At which plate margin can volcanoes occur?

Answer 39

Shield volcanoes form at constructive margins

Composite volcanoes form at destructive margins

Question 40

Describe the primary effects of the Nepal earthquake

Answer 40

9,000 deaths
20,000 people injured
3 million without a home
US$5 billion of damage
50% shops destroyed
Airport became congested as aid arrived
Schools and buildings destroyed
1.4 million people needed food and water days after the quake

Question 41

Describe the secondary effects of the Nepal earthquake

Answer 41

Ground shaking triggered landslides and avalanches, blocking roads, making relief difficult
Avalanches killed 19 people
A landslide blocked the Kali Gandaki River - causing risk of flood