Hazards

Natural event

Events that occur as a result of natural processes of the Earth.

Hazard

The threat of substantial loss of life, substantial impact upon life or damage to property, socioeconomic disruption & environmental degradation that can be caused by an event (these can be caused by human actions or naturally occuring).

Natural hazard

An event which is perceived to be a threat to people, the built environment & the natural environment (occur in the physical environments of the atmosphere, lithosphere & hydrosphere).

Disaster

Occurs as a result of the hazard involving enormous impacts on people or property - a major natural hazard event.

Criteria (at least one met):

• 10+ people killed

• 100+ people affected

• State of emergency declared by government

• Request by government for international assistance

3 Types of Hazard

• Geophysical Hazards: driven by Earth’s own internal energy sources.

• Atmospheric Hazards: driven by atmospheric processes.

• Hydrological Hazards: driven by water bodies, mainly oceans.

Hazard Perception

The way in which someone understands/interprets a hazard.

Risk (definition)

The exposure of people, their possessions & the built environment to a hazardous event.

Risk (formula)

Risk = (Frequency/Magnitude of hazard x Level of Vulnerability)/Capacity of Population to Cope

Factors affecting Hazard Vulnerability

• Location (close to hazard origin e.g. Pacific Ring of Fire)

• Wealth (low = forced to live in hazard-vulnerable areas without suitable building materials)

• Level of technology

• Education

• Urbanisation (mainly LICs: forces poor into high-risk urban areas, vulnerability increasing as unsustainable development = poor land use/degradation)

• Person (very young/old = dependent populations, women more vulnerable)

• Changing risk (rising sea levels/deforestation)

• Cost vs Benefits (e.g. fertile soils)

Class-quake

Hazards that are unequal in the way that they affect people

Capacity of Population to Cope

Ability for a community to absorb & recover from a hazard

Fatalism

An acceptance that hazards are natural events that we can do little to control & losses have to be accepted

Risk sharing

Idea that loss from natural hazards can be modified using aid (sharing the level of risk between the affected countries and those offering aid)

Integrated risk management

Considering social, economic, political factors involved in risk analysis to minimise damage/disrupction

3-Stages Park Model (1991) (incl. factors affecting disruption & defining stages)

(bear in mind QoL may also increase due to a hazard in the long-term)

• Type of hazard

• Intensity/magnitude

• Immediate environment

• Infrastructure

• Relief: immediate response of aid e.g. medical attention, rescue services, overall care (few hours to several days)

• Rehabilitation: people try to return to normal by providing food, water, shelter for most affected (few days to weeks)

• Reconstruction: infrastructure/property reconstructed & crops regrown, people use experience for better response to next hazard (weeks to several years)

5-Stages Park Model: additional 2 stages

1. Preparation: modifying cause/event

2. Hazard event: QoL dramatically deteriorates & people respond with protection

Hazard Management Cycle

• Preparedness: increases in areas of high risk

Evaluating Park Model

Strengths:

• Charts the stages (QoL) following disaster

• QoL is clear indicator of the impact of hazard

• Can clearly visualise impact

• Shows clearly level of normality, impact of hazard & impact of recover on QoL

• Useful for understanding how prepared a community was & how successful it has been in response

• Models can be used to compare events to understand what factors worsen impact

• Clearly shows rate of recovery

• Very versatile (can be applied to many hazards)

• Allows for disaster planners to prepare for normal progression through a disaster event

• Includes temporal dimension

Weaknesses:

• No quantitative data (e.g. death toll)

• Doesn’t show what was done before event to help mitigate

• Can’t show when a country gets hit by another hazard whilst still recovering from an initial event

• Can’t show when a hazard impacts multiple locations

• Might not show full picture of events

Evaluation of Hazard Management Cycle

Strengths:

• Focus on management of hazard (before & after event)

• Can be used to speed up recovery from events by providing a model of action pre/post-event

• 4 stage sequenced framework for managing hazards

• Clear mitigation stage

• Cyclical (ongoing) modal

Weaknesses (* = most impactful):

• *Doesn’t refer to QoL/speed of response

• More basic than Park model

• Less visually representative

Features of Crust

• Continental: thicker, less dense, older/permanent, mainly granite

• Oceanic: thinner, denser, newer, recycled via subduction, mainly basalt

Thickness:

• Continental: 30-40 km thick below continents, <70 in highest mountain ranges

• Oceanic: 6-10 km thick

Features of Mantle

• 2,900 km

• Elements: silicate rocks rich in magnesium/iron

• Asthenosphere: plastic & moves very slowly due to high pressure/temperatures > convection currents > plate movement

• Lower mantle: hotter/denser than upper mantle, intense pressure keeps lower mantle solid

Features of Core

• Outer Core: semi-molten (liquid iron/nickel), responsible for Earth’s magnetic field

• Inner Core (>5,000*C): solid ball (iron) due to extreme pressures

• Primordial heat/radio. decay > hottest part of Earth > drives tectonic activity

• Diameter: 1,200 km

The boundary between crust & mantle

Mohorovičić discontinuity

The boundary between lithosphere & asthenosphere

Isotherm (1,300*C)

Evidence of Continental Drift:

- Geological: jigsaw shape of continental shelves & similar rock sequences in areas now far apart

- Biological: similar fossils found in areas that are now far apart

- Climatological: location of natural resources & glacial markings > some areas have changed drastically