Topic 3 Examples (Geog)

Cards (15)

  • Nature of hazards including chemical composition of magma
    Type of magma determines if the eruptions will be explosive and effusive (non-explosive)
  • Nature of hazards including chemical composition of magma
    Low Silica Lava (Often Effusive)
    • Flows a long distance before cooling and solidifying
  • Nature of hazards including chemical composition of magma
    Low Silica Lava (Often Effusive)
    Example :
    • In 2018, Kilauea in Hawaii erupted, resulting in only 24 injuries but destroyed more than 700 homes. The property damage amounted to USD$800 million.
  • Nature of hazards including chemical composition of magma
    High Silica Lava (Often Explosive)
    • Flows a shorter distance before cooling and solidifying
  • Nature of hazards including chemical composition of magma
    High Silica Lava (Often Explosive)
    • It may form highly destructive pyroclastic flows, causing widespread damage to infrastructures, significant injuries and loss of lives.
    • The explosion of volcanic materials such as volcanic bombs may strike people and properties
  • Nature of hazards including chemical composition of magma
    High Silica Lava (Often Explosive)
    Example:
    • In 2010, the eruption of Mount Merapi in Indonesia resulted in pyroclastic flows that travelled 3km down the the heavily populated mountain sides, destroying properties and killing many. Volcanic bombs were ejected and spread over a distance of 10 km. This violent eruption resulted in the evacuation of 350,000 people and 353 lives were lost.
  • Vulnerable conditions
    Availability of surface and ground water in the development of lahars
    • The greater the availability of surface and groundwater, the more likely lahars will develop.
  • Vulnerable conditions
    Availability of surface and ground water in the development of lahars
    The availability of water in an area depends on the following:
    • Rapid melting of snow and ice on the volcano’s summit just before or during an eruption
    • Groundwater released through cracks and fractures during a volcanic eruption
    • Heavy rainfall
    • Existing rivers or lakes nearby
  • Vulnerable conditions
    Availability of surface and ground water in the development of lahars
    • Lahars can bury and destroy properties, increasing the likelihood of injuries and loss of lives.
  • Vulnerable conditions
    Availability of surface and ground water in the development of lahars
    Examples:
    • Many lahars following the 1991 eruption of Mount Pinatubo, Philippines were triggered by heavy rain associated with the monsoon season, destroying more than 100,000 homes.
    • 2017 Mt Agung volcanic eruption where a tropical cyclone resulted in winds and higher rainfall which resulted in lahars being directed towards popular beaches
  • Vulnerable conditions
    Prevailing wind conditions affecting direction and distribution of ashfall and tephra
    • If travels in the direction where there is a higher human settlement, there will be an increase in disaster risk
    • Higher the speed, the further ashfall and tephra are likely to be dispersed, and more areas are affected, causing more places to be vulnerable
  • Vulnerable conditions
    Prevailing wind conditions affecting direction and distribution of ashfall and tephra
    • Prolong exposure may lead to respiratory problems
    • Properties may be damaged by the weigh of ashfall
    • Ash that falls on farmlands cover and suffocates crops
  • Exposure (Presence of Human Settlement)
    If a volcanic eruption occurs in an area that is populated with dense human settlement, the disaster risk from a volcanic eruption is high.
    There is a greater potential for the loss of lives and destruction of properties than if the volcanic eruption occurred underwater, which is devoid of human settlement.
  • Exposure (Presence of Human Settlement)
    Why do people still choose to live in volcanically active areas?
    • Rich, fertile volcanic soils which are ideal for farming
    • Harnessing geothermal energy from naturally occurring hot water and steam, which can be used to provide electricity
    • Valuable minerals such as sulfur which can be mined
  • Exposure (Presence of Human Settlement)

    Mount Sinabung in Indonesia has experienced several explosive eruptions since 2010. Nonetheless, many continue to live and work within the ‘red zone’ , thereby increasing their exposure to volcanic hazards. This is because there are rich, fertile soils which are ideal for farming