Topic 3, Chapter 3.2, Part 2
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Questions and Answers

Which characteristic of magma is most closely associated with effusive volcanic eruptions?

  • Presence of volcanic bombs
  • Low viscosity (correct)
  • High silica content
  • High gas content

    • Pyroclastic flows are more commonly associated with volcanoes that erupt magma with low silica content.

    False (B)

    What is the primary factor that determines whether a volcanic eruption will be explosive or effusive?

    Silica content of the magma

    The 2010 eruption of Mount Merapi in Indonesia caused death and widespread damage due to highly destructive ______ flows.

    <p>pyroclastic</p> Signup and view all the answers

    Match the volcanic hazard with its primary contributing factor:

    <p>Pyroclastic Flow = High Silica Magma Lahars = Abundant Surface/Groundwater Widespread Lava Flows = Low Silica Magma Volcanic Bombs = Violent Eruption</p> Signup and view all the answers

    Which characteristic of magma is most associated with violent volcanic eruptions?

    <p>High silica content (B)</p> Signup and view all the answers

    Eruptions with low-silica magma are typically associated with pyroclastic flows and widespread devastation.

    <p>False (B)</p> Signup and view all the answers

    What type of secondary hazard is most directly linked to the availability of surface and groundwater during or after a volcanic eruption?

    <p>lahars</p> Signup and view all the answers

    The 2016 Kilauea eruption in Hawaii, characterized by ______ magma, resulted in significant property damage but relatively few injuries.

    <p>low-silica</p> Signup and view all the answers

    If a volcano, irrespective of its magma composition, is located in a region with substantial snow and ice cover and is entering a period of increased volcanic activity, which of the following represents the most critical immediate risk to nearby communities?

    <p>The formation of lahars triggered by rapid snow and ice melt. (B)</p> Signup and view all the answers

    How does an increase in the availability of surface and groundwater affect the likelihood and impact of lahars in volcanic regions?

    <p>It increases both the likelihood of lahar formation and the overall disaster risk due to increased exposure. (B)</p> Signup and view all the answers

    During a volcanic eruption, what role does groundwater play in the formation of lahars?

    <p>Groundwater can be released through cracks and fractures during an eruption, contributing to lahar formation. (D)</p> Signup and view all the answers

    What hydrometeorological factor significantly contributed to the severity of lahars following the 1991 Mount Pinatubo eruption?

    <p>Heavy rainfall due to the monsoon season, saturating the volcanic ash deposits. (B)</p> Signup and view all the answers

    Which of the following describes the most direct impact of lahars on communities located near a volcano?

    <p>The burial and destruction of properties, leading to injuries and fatalities. (C)</p> Signup and view all the answers

    Consider a scenario where a volcano is located in a region experiencing both heavy rainfall and rapid snowmelt. What is the most likely primary consequence?

    <p>An increased risk of lahars due to the saturation of volcanic materials. (A)</p> Signup and view all the answers

    How does the chemical composition of magma indirectly affect earthquake risks?

    <p>By influencing the type and intensity of volcanic eruptions. (A)</p> Signup and view all the answers

    The availability of surface and ground water does not influence the severity of damage from earthquakes.

    <p>False (B)</p> Signup and view all the answers

    What geological phenomenon can occur in water-saturated soil during an earthquake, leading to increased damage?

    <p>Liquefaction</p> Signup and view all the answers

    Disaster risks from seismic activity are not _______ across different locations, due to variations in factors such as water availability and local soil conditions.

    <p>uniform</p> Signup and view all the answers

    Imagine two locations with identical building structures. Location A is situated on dry, compact soil, while Location B is on water-saturated, loose soil. If an earthquake of equal magnitude strikes both locations, which area would likely experience more severe damage, and why?

    <p>Location B, due to the increased risk of liquefaction in water-saturated soil. (A)</p> Signup and view all the answers

    Flashcards

    Low Silica Magma

    A type of magma that is less viscous and leads to gentle, effusive eruptions.

    High Silica Magma

    More viscous magma that causes violent eruptions, including pyroclastic flows.

    Pyroclastic Flow

    A fast-moving current of hot gas and volcanic matter that causes widespread destruction.

    Lahars

    Volcanic mudflows formed by the mixing of volcanic material with water, posing significant risks.

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    Impact of Eruptions

    Volcanic eruptions can cause infrastructure damage, injuries, and fatalities depending on magma type.

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    Volcanic Eruption Types

    Classified based on the magma's silica content, determining explosiveness and lava flow.

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    Effects of Low Silica Magma

    Typically leads to gentle, effusive eruptions causing property damage but fewer casualties.

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    Destructive Nature of High Silica Magma

    Results in explosive eruptions and dangerous pyroclastic flows, causing injuries and fatalities.

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    Lahar Triggers

    Lahars can occur from rapid melting, rainfall, or groundwater release, increasing risk during eruptions.

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    Impact of Lahars

    Can destroy homes and infrastructure significantly, as seen after Mount Pinatubo's eruption.

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    Availability of Surface Water

    Increased surface water makes lahars more likely to occur.

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    Disaster Risk Increase

    Greater water availability raises the risk to people and buildings.

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    Lahars and Property Damage

    Lahars can bury and destroy properties, leading to injuries and deaths.

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    Sources of Lahars

    Lahars can result from melting ice, groundwater, lakes, rivers, or heavy rain.

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    1991 Mount Pinatubo Example

    Heavy rains after the eruption led to 100,000 destroyed homes due to lahars.

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    Factors Affecting Earthquake Damage

    Several elements like magma composition and soil characteristics influence earthquake impacts.

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    Magma Composition

    The chemical makeup of magma affecting eruption types and intensities, influencing earthquake risk indirectly.

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    Impact of Water on Earthquake Damage

    Surface and ground water availability can increase vulnerability of structures to earthquake damage.

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    Liquefaction

    A phenomenon where water-saturated soil loses strength during an earthquake, causing buildings to sink.

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    Geological Characteristics

    Local soil and rock features that affect earthquake severity and impact on infrastructure.

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    Study Notes

    Chemical Composition of Magma (Nature of Hazard)

    • Magma type determines if an eruption is explosive or effusive

    • Low silica magma:

      • Less viscous (thick, sticky)
      • Gentle, effusive eruptions
      • Lava flows far, damages infrastructure over large areas
      • Rarely kills people (they can avoid lava flows).
      • Example: 2016 Kilauea eruption (Hawaii)
        • 24 injuries
        • 600 homes destroyed
        • $800 million damage

    • High silica magma:

      • More viscous
      • Violent eruptions
      • Highly destructive pyroclastic flows (widespread damage, injuries, and deaths)
      • Volcanic bombs may strike people, causing injuries and death.
      • Example: 2010 Mount Merapi eruption (Indonesia)
        • Pyroclastic flow traveled 3 km
        • Volcanic bombs spread over 10 km

    Availability of Surface and Groundwater (Vulnerable Conditions)

    • Greater availability of surface and groundwater increases the likelihood of lahars.
    • More people and buildings are exposed, increasing disaster risk.
    • Sources:
      • Rapid melting of snow and ice on volcano's summit (before/after eruption)
      • Groundwater released through cracks and fractures during eruption
      • Existing lakes and rivers
      • Heavy rainfall
    • Lahars bury and destroy property, increasing injuries and deaths.
    • Example: 1991 Mount Pinatubo eruption (Indonesia)
      • Many lahars following the eruption
      • Heavy rain (monsoon season)
      • More than 100,000 homes destroyed

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    Description

    This quiz explores the nature of hazards related to different magma types and their effects during volcanic eruptions. Learn about low and high silica magma, their eruption styles, and the resulting impacts on communities, using recent volcanic examples to illustrate these concepts.

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