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GCSE Geography > GCSE Natural Hazards > Flashcards

GCSE Natural Hazards Flashcards

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1
Q

What is a constructive plate boundary?

Can you give an example?

A

This is where two plates move apart.
As the plates move apart magma from the mantle rises up to fill the space.
Volcanic eruptions occur here, often under water.
An example - the North American plate and Eurasian plates are moving apart in Iceland.

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2
Q

What is a destructive plate boundary?

Can you give an example.

A

This is where two plates are moving apart.
The oceanic plate is denser (heavier) and is subducted (pushed) under the lighter continental plate.
The subducted plate is melted by the heat of the mantle, and this material is returned to the surface as a volcano.
Earthquakes are also common here.
An example - the Pacific plate is being pushed under the Eurasian plate in Japan.

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3
Q

What is a collision plate boundary?

Can you give an example?

A

This is where two plates collide.
Neither plate is subducted as they are both continental, so instead as they crash into each other they are forced upwards and form mountains.
An example - the Indo-Australian plate and the African plate collided to form the Himalayas.

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4
Q

What is a conservative plate boundary?

Can you give an example?

A

This is where two plates slide past each other at different speeds.
As they slide past friction builds up.
When this friction becomes too great it is released as an earthquake.
An example - the North American plate is sliding past the Juan de Fuca plate along the San Andreas fault.

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5
Q

What is a convection current?

A

Radioactive decay in the core causes heat to be generated.
The heat rises from the inner and outer core, through the mantle.
When it reaches the underside of the crust, the majority is unable to break through so travels along the underside of the crust.
This material is sticky so pulls the crust along with it.
As the material cools it sinks back towards the core, and new heated material rises upwards.

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6
Q

What is the difference between the epicentre and the focus of an earthquake?

A

The focus is the point deep inside the earth where an earthquake starts.

The epicentre if the point on the earths surface where an earthquake is felt by humans and seismograph machines.

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7
Q

What are some of the primary effects of an earthquake?

A
  • Homes destroyed
  • Transport links destroyed
  • People killed
  • Avalanches / landslides
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8
Q

What are some of the secondary effects of an earthquake?

A
  • Disease due to all the dead bodies
  • Deaths are medical supplies can’t get though
  • Fires as gas and power lines are destroyed
  • Loss of money to the economy as services are disrupted / destroyed
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9
Q

How do tropical storms form?

A

Sea surface temperature of at least 26°C, which is why they usually occur over tropical seas between 5 and 20° north or south of the equator.
The warm and wet air rises, it condenses to form towering clouds, heavy rainfall (this creates a low pressure zone)
More rising warm air causes the pressure to decrease at higher altitudes, so the cold air to be ‘sucked in’
This causes the mixing warm and cold air t begin to spiral at very high speeds - anti-clockwise in the northern hemisphere
Air is ejected at the top of the storm
The faster the winds blow, the lower the air pressure in the centre, and so the hurricane grows stronger and stronger.
Seen from above, hurricanes are huge circular bodies of thick cloud around 450 km (300 miles) wide

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10
Q

Why do some people choose to live near volcanoes?

A
  1. The dramatic scenery created by volcanic eruptions attracts tourists. This brings income to an area
  2. The lava and ash deposited during an eruption breaks down to provide valuable nutrients for the soil. This creates very fertile soil which is good for agriculture
  3. The high level of heat and activity inside the Earth, close to a volcano, can provide opportunities for generating geothermal energy
  4. Due to increasing population there are now larger numbers of people who are forced to live near volcanoes - such as in Naples near Mt. Versuvius
  5. Some people do not want to move from their homes as the volcano may not erupt frequently, so they assume it will not affect them
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11
Q

What are some of the negatives of living near a volcano?

A
  1. Many lives can be lost as a result of a volcanic eruption
  2. If the ash and mud from a volcanic eruption mix with rain water or melting snow, fast moving mudflows are created. These flows are called lahars
  3. Pyroclastic flows can travel very quickly (up to 60mph) so they are very difficult to escape
  4. Lava flows can destroy settlements and clear areas of woodland or agriculture
  5. Human and natural landscapes can be destroyed and changed forever
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12
Q

What is the scale used to measure the magnitude (strength) of an earthquake?

A

The Richter Scale

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13
Q

What are the 4 parts of the Earth? (from inner to outer)

A
  1. Inner core
  2. outer core
  3. Mantle
  4. Crust
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14
Q

What is a wildfire?

A

The uncontrolled burning of combustible material (material that is easy to burn)

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15
Q

What are some of the human causes of wildfires?

A
  1. Campfires
  2. Disguarded cigarettes
  3. Arson (deliberately setting it on fore)
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16
Q

What are some of the natural causes of wildfires?

A
  1. Lightning
  2. Volcanic lava
  3. Dry conditions and hot temperatures
17
Q

How can you protect your home from a wildfire?

A

Create a clear zone around your home with no flammable material in it and if you have a garden keep the grass watered

Make your property out offline retardant material

Make sure there is space between your property and others

Thin out trees close to your house so there is less material if a fire does start

18
Q

What is an earthquake?

A

The sudden release of built up pressure as two plates slide past each other.

19
Q

Why is the damage caused by tropical storms often more devastating in an LEDC? (E.g. The Philippines)

A

Higher population density

More slum settlements - the houses in them are not regulated by strict rules so are easily destroyed

Limited access to warning systems

Poor medical care and facilities to help people who are injured

Not as much money available to develop new buildings

20
Q

Why was Hurricane Katrina so devastating to the southern USA?

A

A large number of people lived on the floodplain of the River Mississippi so when the levees broke the land was flooded.

A large housing area of poor Black Americans was damaged by the winds and water, with many of them not having insurance so there homes are still damaged today.

The economy was massively disrupted as infrastructure was damaged and businesses were flooded.

Looting was a massive issue, as many people affected were poor.

21
Q

What can be done to protect buildings from earthquakes?

A
  1. Pendulum buildings
  2. Shock absorber foundations (also called base isolators)
  3. Reinforced walls
22
Q

How does a pendulum building help protect against an earthquake?

A

A weight ia built into a tall building which sways the opposite way to the earthquake. This helps the building stay standing.

This method has been used in the Skytree News Tower in Tokyo.

23
Q

On what type of plate boundary/boundaries would we find volcanoes?

A

Constructive - E.g. Iceland where the North American and Eurasian plates are pulling apart

Destructive - E.g. Japan where the Pacific plate is being subducted beneath the Indo-Australian and Philippine plates

24
Q

Where are most volcanoes and earthquakes found?

A

The ‘Ring of Fire’ in the Pacific Ocean

25
Q

What is machine called that measures the magnitude (strength) of an earthquake?

A

Seismograph

26
Q

Why do both earthquakes and volcanoes occur on a destructive plate boundary?

A

As the oceanic plate and the continental plate move towards each other, the oceanic plate is subducted (pushed under) as it is denser (heavier).
As the plate is pushed down into the mantle it is heated and melts.
This melted material is forced back to the surface as a volcano.

Earthquakes are caused as when the oceanic plate is being subducted under the continental plate friction is generated.
This friction builds up, and when it becomes too great it is released as an earthquake.

27
Q

How could an LEDC prepare for a tropical storm?

A
  1. Have warning sirens to alert people
  2. Build emergency shelters for people to go to
  3. Encourage people to create an emergency kits (with food, water, first aid, clothes, etc.)
28
Q

Why can the damage of a tropical storm be high in an MEDC?

A
  1. High population density - lots of people living in a small area will be effected
  2. The buildings and infrastructure is expensive so will cost a lot to replace if it is damaged.

An example of a severe and expensive tropical storm was Hurricane Katrina which hit the USA in August 2005.

Cost of damage - $135 billion

Displaced from home - over 1 million

Deaths - over 1,800

29
Q

What is population density?

A

This means the number of people living in an area.

A high population density means there are lots of people living in that area (E.g. like a city environment)

A low population density means there are fewer people living in that area (E.g. like the countryside)

30
Q

Describe a shield volcano.

Where might we find one?

A

Low sides that covers a large area.
Thin, runny lava.
Frequent, but non-violent eruptions.

Example - Kilauea, Hawaii

31
Q

Describe a composite volcano.

Where might we find one?

A

Steep sides.
Thick, sticky lava.
Violent eruptions - frequency varies depending upon the location.

Example - Mt. Fuji, Japan

32
Q

What is a tsunami?

A

An earthquake that occurs underwater and produces a large wave.

The word tsumani is Japanese for ‘harbour wave’

33
Q

Where do most tropical storms occur?

A

Around the equator where the water is above 26oc

GCSE Geography (4 decks)

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