Physical Geography > Hazards > Flashcards

Hazards Flashcards

(43 cards)

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1
Q

What is a natural hazard?

A

A natural event that poses a threat to human life and/or property

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2
Q

What is a natural disaster?

A

A natural hazard that has caused significant damage/deahts
A natural hazard that has caused one of the following:

  • 10 or more deaths
  • 100 or more people affected
  • A request for international assistance
  • A declaration of a state or emergency
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3
Q

What are factors affecting the severity of a hazard?

A
  • Natural factors (eg. geology, tides)
  • Magnitude
  • Population density and distribution
  • Management
  • Frequency
  • Education
  • Level of development
  • Time
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4
Q

What is hazard perception?

A

How a person views how dangerous hazards are and what risks they pose -> influences how they react to hazards

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5
Q

What are factors influencing perception of a hazard?

A
  • Wealth
  • Education
  • Experience
  • Religion/cultural beliefs
  • Occupation
  • Family
  • Values, personality
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6
Q

What are the different types of human responses to hazards?

A
  • Fatalism
  • Prediction
  • Adaptation
  • Mitigation
  • Fear
  • Management
  • Risk sharing/community preparedeness
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7
Q

What is fatalism?

A

The viewpoint the hazards are uncontrollable natural events and any losses should be accepted as nothing can be done to stop them

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8
Q

What is prediction?

A

Using scientific research and past events in order to know when a hazard
will take place, so that warnings may be delivered and impacts of the hazard can be reduced.

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9
Q

What is adaptation?

A

Attempting to live with hazards by adjusting lifestyle choices so that
vulnerability to the hazard is lessened

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10
Q

What is mitigation?

A

Strategies carried out to lessen the severity of a hazard

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11
Q

What is fear?

A

When people feel so vulnerable that they leave the area to live in a safer area

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12
Q

What is management?

A

Coordinated strategies to reduce a hazard’s effects. This includes
prediction, adaptation, mitigation

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13
Q

What is risk sharing?

A

A form of community preparedness, whereby the community shares the
risk posed by a natural hazard and invests collectively to mitigate the impacts of future
hazards.

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14
Q

What is a geophysical hazard?

A

A hazard caused by land processes that is primarily driven by tectonic plate movements (eg. earthquake)

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15
Q

What is an atmospheric hazard?

A

A hazard caused by atmospheric processes and the conditions created
because of these, such as weather systems (eg. wildfires)

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16
Q

What is a hydrological hazard?

A

A hazard cause by the movement or related to the distribution of water (eg. flooding)

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17
Q

What are hazards that are both hydrological and atmospheric called?

A

Hydrometeorological hazards (eg. tropical storms)

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18
Q

Describe the Park Model

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A

The Park Model demonstrates how a disaster has varying impacts over time by showing quality of life against time. It includes the pre-disaster, relief, rehabilitation and reconstruction stages. Can be used to compare hazards

19
Q

Describe the Hazard Management Cycle

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A

It is a continuous loop which outlines an approach to managing a hazard, involving preparedness, response, recovery and mitigation phases

20
Q

Outline the structure of the Earth from the outside towards the inside

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A
  • Crust (thin top of the Lithosphere) - can be oceanic or continental
  • Lithosphere (crust and rigid upper section of mantle) - split into plates
  • Asthenosphere (semi-molten layer) - constantly moving due to convection currents powered by heat from the core
  • Mantle (molten and semi-molten rocks) - high silicon content
  • Core (inner and outer) - inner solid, outer molten, iron/nickel alloys
21
Q

Outline older, observed evidence for plate tectonic theory

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A
  • Jigsaw theory (Africa and South America)
  • Mesosaurus fossils found both in Brazil and South Africa despite the Mesosaurus being a freshwater reptile unable to cross the Atlantic
  • Matching geology -> São Francisco Craton (Brazil) matches the Congo Craton (Africa) in rock age and composition, when the continents are fitted together, these rock belts line up almost perfectly.
22
Q

Outline modern evidence of plate tectonic theory

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A
  • GPS/satellite tracking -> eg. at the San Andreas fault, the Pacific plate moves around 10cm/year faster than the North American plate
  • Radiometric dating -> oceanic crust at the Mid-Atlantic ridge is less than 1 million years old but further away, towards the east coast of the US, the crust is around 200 million years old -> supports sea floor spreading
23
Q

What is sea floor spreading?

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A

The process where new oceanic crust is formed at mid-ocean ridges and spreads laterally, pushing older crust away

24
Q

What is gravitational sliding/ridge push

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A

Magma rises at the ridge and forms new oceanic crust which is elevated due to heat and buoyancy. As it cools and thickens, it becomes denser and gravity causes the cooling plate to slide downslope away from the ridge.

25
What is slab pull?
The heavier, denser oceanic plate subducts under the less dense continental plate. As the plate sinks, gravity pulls the plate down into the mantle -> drags the entire plate towards the benioff zone
26
Explain the formation of rift valleys
- As two continental plates move apart, the brittle crust fractures into sections - Some drop down to form the rift valley and the sections left standing above the valley are called horsts - As the plates continue to move apart, the valley will continue to drop and extend, eventually allowing ocean water to flood the valley - Example is the East African Rift Valley
27
Explain the formation of ocean ridges
At constructive plate boundaries with oceanic plates underwater, convection currents drive plates away from each other. Ridge push occurs when magma rises where the crust is pulled apart and extrudes, which cools and solidifies. Over time this repeated process forms long ridges underwater such as the Mid-Atlantic Ridge.
28
How do deep sea trenches form?
Deep sea trenches form at destructive boundaries when the denser plate subducts the other plate. The denser oceanic plate is pulled into the asthenosphere via slab pull and this causes the lithosphere and the sea floor to form a steep V shaped depression. Example is the Peru-Chile trench (Nazca subducts South American)
29
How do island arcs form?
Island arcs form at destructive plate boundaries when the subducting ocean plate melts and rises due to its lower density. This rises through the fractured continental plate and forms offshore volcanoes known as island arcs. An example is the Aleutian Islands (Pacific subducts North American)
30
What proportion of active volcanoes lie on the Pacific Ring of Fire?
75%
31
What is used to measure the magnitude of volcanic eruptions?
VEI (Volcano Explosivity Index), scale 0 to 8
32
What are magma plumes?
Upwellings of intensely heated rock that rise from the mantle upwards
33
How do hotspots form?
Hotspots form when magma plume wears away the crust until the magma is able to reach the surface, causing volcanoes to form. As the tectonic plate is moving, this leads to island chains forming such as Hawaii, where the volcano furthest away from the active ones are 5 million years older
34
What are pyroclastic flows/Nuees Ardentes
Very hot clouds of burning hot ash, gas and tephra that collapse down a volcano at high speeds -> can reach over 1000 degrees celsius and 430 mph
35
What is tephra?
Any type of rock that is ejected by a volcano, ranging from volcanic bombs to ash
36
What is ash fallout?
When volcanic ash made up of tiny fragments of pulverised rock less than 2mm in diameter covers wide areas
37
What is a volcanic mudflow/lahar?
A destructive, fast moving flow of volcanic ash, rock debris, tephra and water that rushes down a volcano
38
What gases do volcanoes release?
Water vapour, carbon dioxide, sulphur dioxide
39
How does acid rain form?
When fume clouds contain water droplets in which acid gases have dissolved (especially sulphur dioxide). These droplets fall as acid rain
40
What are the types of lava flows?
- Block lava flows - Aa lava flows - Pahoehoe lava flows - Pillow lava
41
What is the spatial distribution of volcanoes?
Volcanoes are generally concentrated in linear clusters at destructive and constructive plate boundaries
42
What is the frequency of volcanic eruptions?
Completely unreliable
43
How do fold mountains form?
Movement of plates at destructive/collision boundaries causes the continental plate to crumple Eg. Andes where the Nazca subducts the South American plate
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