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Geography IBDP > Geophysical hazards > Flashcards

Geophysical hazards Flashcards

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1
Q

What are the 5 main mechanics of plate movement?

A

Internal heating

Plumes

Subduction

Rifting at margins

Convection currents

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2
Q

What are the 2 main sources of heat flow within the Earth?

A

Radiogenic - decay of materials

Primordial heat - heat lost by earth as it begins to cool

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3
Q

Describe convection currents

A

Hot magma near to the core to the surface heats up, becoming less dense and so moving upwards and spreads out at mid-ocean ridges.

The cold solidified crust sinks back into the earth’s interior because it is heavier and denser than the surrounding material.

This is caused by heat from radioactive decay of uranium and potassium in mantle

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4
Q

Describe the distribution of earthquakes

A
  • occur near plate boundaries
  • For example: centre of Atlantic ocean in association with mid-atlantic ridge
  • There are many earthquakes around the edge of the Pacific Ocean
  • Broad belts of earthquakes
  • some anomalies
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5
Q

Describe the human causes of earthquakes

A
  • construction of large dams
  • mining
  • testing of weapons
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6
Q

Describe the distribution of volcanoes

A
  • found at plate boundaries
  • some occur over hotspots
  • Pacific Ring of Fire - most active volcanoes
  • some occur in the middle of the ocean e.g: Hawaii.
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7
Q

Describe a hotspot

A

A hotspot is a plume of hot material rising from the deep within the mantle, responsible for volcanoes.

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8
Q

Where are landslides common? Give examples of some regions in the world

A
  • areas with active tectonic processes
  • high rainfall
  • high population density

Examples:

  • Southern Edge of the Himalayas
  • Central China
  • South West India
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9
Q

What is a recurrence interval or return period?

A

The expected frequency of occurrence measured in years for an event of a particular size.

Small events have a short return period whereas large events have a high return period.

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10
Q

Units for recurrence interval?

A

Years

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11
Q

Earthquake frequency and magnitude

A

The richter scale was used, logarithmic. But now M scale is being used. Moment magnitude scale which measures the amount of energy released.

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12
Q

How is strength of a volcano measured?

A
  • Volcanic Explosive Index
  • based on amount of material ejected in the explosion
  • height of cloud it creates
  • damage caused
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13
Q

Describe vulnerability

A

The geographic conditions that increase the susceptibility of a community to a hazard

Not only physical effects of a hazard, but also status and property of people

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14
Q

Describe the economic factors that influence vulnerability (5)

A

Quality of housing

Building styles and codes

Access to technology

Warnings and forecasting

Insurance cover

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15
Q

Describe the social factors that influence vulnerability (4)

A

Education - high education means more income, better quality housing

Public education about how to deal with events

Awareness of hazards

Gender - many women may feel responsible for children/elderly following an event

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16
Q

How do demographic factors affect vulnerability (3)

A

Population density

Age - elderly less mobile

Disability

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17
Q

How do political factors affect vulnerability (2)

A

Nature of society - provision of aid

Effectiveness of lines of communication

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18
Q

Geographic factors affecting impacts of a geophysical event? (8)

A
  • Magnitude and frequency
  • Population density
  • Type of buildings
  • Time of day
  • Distance from event
  • Types of rocks and sediment
  • secondary hazards
  • economic development
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19
Q

Definition of risk

A

A risk is the likelihood of the loss of life, injury, destruction or damage

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20
Q

Factors affecting the perception of risk?

A
  • Experience - the more experience of hazards, the more people become adjusted
  • Material well-being: those who are better off have more choice
  • Personality
21
Q

Describe how hazards are characterized (hazard profile)

A
  • Magnitude
  • Frequency
  • Duration
  • Areal extent
  • Spatial concentration
  • Speed of onset
  • Regularity
22
Q

Describe the trend in geophysical hazards

A

Remained broadly constant

Earthquakes have killed
more people than all disasters put together

Asia suffered the most

23
Q

How is susceptibility to hazards increasing?

A

Population growth is occurring

Higher population density in highly seismic zones

Slums and squatter settlements expand onto high risk areas such as slopes and embankments

24
Q

How are volcanoes predicted?

A

Seismometers to record swarms of tiny earthquakes that occur as magma rises

Chemical sensors to measure increased SULPHUR levels

Lasers/GPS to detect physical swelling of volcano

Ultrasound to monitor low frequency waves in the magma resulting from the surge of gas and molten rock

Difficult to predict volcano eruption

25
Q

How to predict earthquakes?

A
  • Seismometers
  • Magnetometer
  • Near-surface seismometer
  • Vibroseis truck
  • Strain meter
  • Sensors in wells
  • Satellite relays
  • Laser survey equipment
26
Q

How does a seismometer work?

A

To record micro-earthquakes

27
Q

How does a magnetometer work?

A

To record changes in the earth’s magnetic field

28
Q

How does a near-surface seismometer work?

A

To record larger shocks

29
Q

How does a vibroseis truck work?

A

To create shear waves to probe the earthquake zone

30
Q

How do sensors in wells work?

A

To monitor changes in groundwater levels

31
Q

How do satellite relays work?

A

To relay data to the US geological survey

32
Q

How does laser survey equipment work?

A

To measure surface movement

33
Q

How to prepare for geophysical hazard adaptation: preparedness

A

Land-use zoning is an important adaptation
Different land uses may be prevented from locations in a zone that is known to be at risk of a hazard e.g: hospitals should not be built near fault lines

Take out insurance cover against natural hazards. LIC residents cannot afford insurance even if it is available. It is always much harder to justify spending money on an event that might not occur.

New technology can be used to record the swelling of volcanoes and changes in water chemistry. Mobile phones with GPS can be used to inform agencies about geophysical changes.

34
Q

How to manage landslides?

A
  • Terracing steep slopes
  • Drainage of water from slopes
  • Building restraining structures such as stone walls
  • Erosion control at the base of cliffs
  • Diversion of roads away from active areas
35
Q

How to manage risk for earthquakes?

A
  • Single storey buildings have greater stability than multi-storey
  • Basement isolation: mounting the foundations of a building on rubber mounts which allow the ground to move under the building. This isolates the building from tremors

Building reinforcement strategies e.g: building on foundations built deep into underlying bedrock and use of steel-constructed frames that can withstand shaking.

  • Land-use planning
36
Q

Managing earthquakes in pakistan

A
  • Light walls and gables are lightweight structures which are subject to smaller forces and are less likely to fall when the ground shakes

Quake-resistant houses are being built in Pakistan of straw. Compressed bales are held together by nylon netting and sandwiched between layers of plaster

37
Q

Managing earthquakes in Haiti

A

In Haiti, heavy concrete roofs collpased on many homes; sheet metal roofs on wooden trusses are more resistant

Small, regularly spaced openings create fewer weak spots in walls. But in Haiti, walls were not properly reinforced

38
Q

Peru earthquake management

A

Reinforced walls are made of natural materials such as eucalyptus or bamboo

Walls of some adobe houses have been reinforced with a plastic mesh to prevent collapse.

39
Q

Earthquake management in Indonesia

A
  • Confined Masonry: brick walls are framed and connected to the roof by corner columns and a crown beam of reinforced concrete. In a quake, the structure moves as a unit
  • Shock absorbers: tyres are filled with stones or sand and fastened between the floor and foundation can serve as cheap ground-motion absorbers for many types of buildings.
40
Q

How to control volcanoes?

A
  • divert lava flows using dry channels or explosives or by pumping water onto the lava front to cool it
  • Little can be done to reduce impacts from pyroclastic flows other than to evacuate the area
  • GPS can be used to monitor the swelling of volcanoes, could indicate eruption
41
Q

How to manage the risk of tsunamis?

A

Sea walls

early warning systems

Walls can only provide a certain amount of protection and will not stop bigger waves.

Cost dictates how high the wall can be built

42
Q

Describe the rescue-rehabilitation-reconstruction

A

Rescue = immediate aftermath of a disaster. Sniffer dogs and search and rescue teams

Rehabilitation = refers to people making their homes safe again and live in them again

Reconstruction = fo r some, rehab isn’t possible, so reconstruction is necessary.

RapidFTR created by a student, used to reunite children with their parents in situations.

In exam, write about how there is a different in rehab and reconstruct in HICs and LICs. LICs takes longer than in HICs as government does not have the funds available.

43
Q

Describe the structure of the earth

A

4 layers:

  • crust - thick continental and thin oceanic
  • liquid mantle - constitutes most of it
  • liquid outer core
  • solid inner core
44
Q

Describe shield volcanoes

A
  • no explosive activity
  • basaltic lava which is runny
  • gently sloping sides
  • shallower crater
  • large circumference
  • Mauna Loa - Hawaii example
45
Q

Describe composite volcanoes

A
  • viscous lava
  • alternating layers of lava
  • large crater
  • steep sides
  • active and explosive
  • sometimes parasitic cones grow on the sides e.g: Mount Etna
46
Q

Describe cinder volcanoes

A
  • formed by fragments of solid material which accumulates as a steep conical hill around the vent to form a cone
  • Concave
  • steep angle of 30-40 deg
  • Cinder and ash cones are not very high
  • eg: Volcano de Fuego (has a high cone)
  • violent eruptions
  • lava breaks up into cinders, ash and other fragments
47
Q

Describe volcanic hazards

A

Pyroclastic flows:

  • Ash and debris that has travelled through the air and fallen to the ground is known as pyroclastic deposits.
  • Fine ash particles damage people’s lungs
  • Ash is fairly heavy, thick enough for a building to collapse
  • Travel at speeds over 500km/hr

Landslides:

Lahars:

  • landslide
  • debris becomes saturated with rainwater

Volcanic gases:

  • C02: Cameroon
48
Q

Focus is the top or bottom?

A

BOTTOM - original source of the release of tension

49
Q

Epicentre top or bottom?

A

TOP - surface on Earth immediately above earth

Geography IBDP (4 decks)

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