Understanding Earthquake Hazards
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Which of the following is NOT a type of volcanic hazard mentioned in the text?

  • Earthquake (correct)
  • Ballistic Projectiles
  • Lava Flows
  • Pyroclastic Flow

    • High silica magma results in low viscosity lava flows, moving at high speeds.

    False

    What is the main difference between a pyroclastic flow and a pyroclastic surge?

    A pyroclastic surge is a diluted form of a pyroclastic flow with greater mobility, posing a higher risk to communities.

    The speed of a lava flow is influenced by the ______ of the slope and the ______ of the magma.

    <p>steepness, viscosity</p> Signup and view all the answers

    Which volcanic gas is the most abundant?

    <p>Water Vapor</p> Signup and view all the answers

    Match the following volcanic features with their descriptions:

    <p>Ballistic Projectiles = Large blocks of material ejected during an eruption Pyroclastic Surge = A fast-moving, diluted flow of hot gas and volcanic debris Lava Flow = A stream of molten rock flowing from a volcano Volcanic Gas = A mixture of various gases released during an eruption</p> Signup and view all the answers

    Volcanic gases are only released during an eruption.

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

    Describe one way in which volcanic activity can be monitored to predict potential eruptions.

    <p>Monitoring seismic activity, gas emissions, or ground deformation can indicate changes in volcanic pressure and potentially warn of an impending eruption.</p> Signup and view all the answers

    Which of the following is NOT a sign of an impending volcanic eruption?

    <p>Decrease in steam and gas emissions</p> Signup and view all the answers

    Camiguin is ranked as the province with the highest risk for volcano-related damage.

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

    Name one of the two provinces ranked second for volcano-related risk.

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

    The increased _____ emission is an indicator that magma is close to the surface.

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

    Match each province with its risk level for volcano-related damage:

    <p>Camiguin = Highest risk Sulu = Second risk Biliran = Risk present Albay = Moderate risk</p> Signup and view all the answers

    What is one natural sign that a tsunami may be approaching?

    <p>Ground shaking</p> Signup and view all the answers

    Earthquakes can only cause landslides due to their force and speed.

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

    List one of the three parts that comprise a landslide.

    <p>source, path, or deposit</p> Signup and view all the answers

    Unusual sea level changes can signify a ______ is approaching.

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

    Match the terms related to landslides and their descriptions:

    <p>source = The origin point of a landslide path = The route taken by the sliding material deposit = The area where the landslide material accumulates overloading = Increased weight on a slope that contributes to landslides</p> Signup and view all the answers

    Which of the following is NOT a trigger for landslides?

    <p>High winds</p> Signup and view all the answers

    Landslides can only occur in mountainous regions.

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

    What force is always the primary factor enabling landslides to occur?

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

    Which of the following describes lahar?

    <p>A wet, cement-like mixture of volcanic material and water</p> Signup and view all the answers

    Ashfalls consist of volcanic particles that are all larger than 2 mm in diameter.

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

    What is a significant health hazard associated with ashfall?

    <p>Respiratory diseases</p> Signup and view all the answers

    The explosive materials released from a volcano, including volcanic particles and hot gases, are classified as _________.

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

    What type of current is a pyroclastic flow classified as?

    <p>A dense current that moves slower than a surge and is attached to the ground</p> Signup and view all the answers

    What is tephra?

    <p>Fragmented volcanic particles</p> Signup and view all the answers

    Match the volcanic hazards with their characteristics:

    <p>Lahar = A wet mixture of volcanic material and water Ashfall = Fragmented particles less than 2 mm in diameter Pyroclastic Flow = Dense current of volcanic particles and hot gases Volcanic Gas = Gaseous emissions from volcanic eruptions</p> Signup and view all the answers

    The area where tectonic plates collide, leading to the formation of volcanoes, is known as a __________.

    <p>subduction zone</p> Signup and view all the answers

    What occurs during ground rupture?

    <p>Ground movement causes the surface to break.</p> Signup and view all the answers

    Liquefaction leads to the ground becoming solid and stable.

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

    What can cause earthquake-induced ground subsidence?

    <p>Earthquakes and man-made activities such as over-pumping groundwater.</p> Signup and view all the answers

    Ground shaking can lead to ______, causing grains of soil to mix with water.

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

    Match the following earthquake hazards with their definitions:

    <p>Ground Shaking = Movement of the ground caused by seismic waves Ground Rupture = Breaking of the surface along a fault line Liquefaction = Soil behaves like a liquid Tsunamis = Large ocean waves caused by underwater disturbances</p> Signup and view all the answers

    Which of the following is a consequence of liquefaction?

    <p>Uneven land formation</p> Signup and view all the answers

    Earthquake-induced landslides only occur in mountainous regions.

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

    What is the typical effect of ground shaking on structures in liquefaction-prone areas?

    <p>Structures may collapse.</p> Signup and view all the answers

    What primarily causes land subsidence during an earthquake?

    <p>Ground shaking</p> Signup and view all the answers

    Tsunami waves generated by seismic activity are also known as harbor waves.

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

    What is the term for the gradual sinking of land, which can lead to sinkholes?

    <p>land subsidence</p> Signup and view all the answers

    The displacement of the _____ triggers the formation of tsunami waves.

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

    Match the stages of a seismic-related tsunami with their descriptions:

    <p>Initiation = Refers to the formation of waves due to seafloor displacement Splitting = Involves the division of tsunamis into distant and local waves Amplification = Involves the increase in wave height and decrease in wavelength Runup = Refers to the approach of the tsunami's leading wave to the shore</p> Signup and view all the answers

    What happens to ocean water during the amplification stage of a tsunami?

    <p>The waves increase in height</p> Signup and view all the answers

    Earthquake-induced ground subsidence can lead to an increase in flooding susceptibility in an area.

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

    The term ____________ originates from the Japanese words

    Signup and view all the answers

    What is the main cause of tsunami waves generated by seismic activity?

    <p>Sudden vertical displacement of a column of water</p> Signup and view all the answers

    The term 'tsunami' translates to 'harbor wave' in Japanese.

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

    What is the term for the gradual setting or sinking of land that may lead to sinkholes?

    <p>land subsidence</p> Signup and view all the answers

    The _______ of the seafloor is the initiation stage of a tsunami.

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

    Which of the following describes what happens during the amplification stage of a tsunami?

    <p>Waves increase in height while their wavelength decreases</p> Signup and view all the answers

    Ground shaking during an earthquake can lead to liquefaction, causing soil to become unstable.

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

    Tsunamis generated by seismic movement are also referred to as __________ tsunamis.

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

    Study Notes

    Earthquake Hazards

    • Earthquake hazards include ground shaking, ground rupture, liquefaction, tsunamis, earthquake-induced ground subsidence, and earthquake-induced landslide.

    Ground Rupture

    • Ground ruptures, also known as fissures, are tension cracks where the ground surface breaks due to ground movement.
    • They are commonly found near or along fault lines.
    • Structures built on fault lines are prone to breakage, and significant ruptures can cause damage to transportation, power, and communication lines, as well as water lines underneath.

    Liquefaction

    • Liquefaction is a phenomenon where saturated sediment "liquefies" and behaves like water, flowing.
    • On a normal day, water-saturated ground underneath does not cause destruction.
    • However, ground shaking can disturb underlying materials.
    • Grains loosen and mix with water.
    • The flowing water causes structures to collapse.
    • Common signs of liquefaction include ground water leaking and ground undulation causing uneven land formations

    Earthquake-Induced Ground Subsidence

    • Land subsidence results from human activity, such as over-pumping groundwater, and also, from earthquakes.
    • Earthquake-induced ground subsidence is the sinking of the ground, either gradually or suddenly.
    • Sinking land areas become catch basins for rainwater, which increases flooding risk.
    • Subsidence can cause the development of sinkholes in adjacent areas.

    Tsunamis

    • Tsunamis, of seismic origin, are formed when there's a movement beneath the ocean. This is described as a displacement, initiating the tsunami.
    • Tsunamis are a wave or series of waves in a wave train caused by the sudden, vertical displacement of a column of water.
    • They can be triggered by seismic activity, explosive volcanism, or underwater landslides.
    • The term tsunami comes from Japanese words "tsu" (harbor) and "nami" (wave), also called "harbor wave."
    • Stages of a seismic tsunami include 1. Initiation, 2. Splitting, 3. Amplification, and 4. Runup - During Initiation, the displacement of the seafloor is followed by the displacement of ocean water. - Splitting divides tsunamis into two waves, one heading towards the deep ocean, and the second toward the shoreline. - During Amplification, the waves' height increases and their wavelength decreases, making the shore water recede, exposing parts of the beach. - Runup refers to the tsunami's approach to the shore, accumulating in force. The receding of parts of the wave adds to the height of succeeding leading waves.
    • Natural signs of an impending tsunami include ground shaking near a body of water, unusual sea levels, and the sound of rumbling waves.

    Earthquake-Induced Landslide

    • Earthquakes trigger landslides by combining their effects with the force of gravity.
    • Gravity enables landslides to occur when combined with the triggering of earthquakes.
    • Landslides are defined as a mass movement of rock, soil, and debris down a slope due to gravity.
    • Landslides can occur due to ground vibrations caused by tectonic or volcanic earthquakes.
    • Other triggers for landslides include natural triggers (plant and animal movement), rainfall, weathering of rocks, and human activities (excessive mining, massive urbanization in unstable areas).
    • Factors that increase landslide potential in a region are steep slopes, unstable landmass from the weakening of slope material, weathering of rocks affecting slope condition over time, and the overloading of slopes by human activity.
    • Landslides are divided into 3 parts: Source, Path, and Deposit.

    Volcano Hazards

    • Volcano hazards include Lahar, Ashfall, Pyroclastic Flow, Ballistic Projectiles, Volcanic Gas, and Lava Flow.

    Lahar

    • Lahars are wet cement-like mixtures of volcanic material and water, originating from Indonesia.
    • Lahars carry fresh volcanic materials (pyroclastic flows and ashfalls).
    • Lahars are dangerous due to their thickness and toxic chemicals, making survival impossible.

    Ashfall

    • Ashfall events consist of fragmented volcanic particles less than 2mm in diameter.
    • Ashfall follows a volcanic eruption, creating an ash column that settles, blanketing affected areas.
    • Ashfall events can have respiratory health hazards, damage skin, and contaminate water sources.

    Pyroclastic Flow

    • Pyroclastic flows are the results of volcanic explosions.
    • They are dense currents of volcanic particles (pyroclastic, hot gases, and ashes) rushing down from the volcano's mouth after an explosion.
    • Pyroclastic flows are classified by density and viscosity into flow (slower movement attached to the ground) and surges (more mobile currents, with higher risk to communities).

    Ballistic Projectiles

    • Ballistic projectiles, or large blocks/bombs, are volcanic materials (not flows).
    • They are ejected from a volcanic vent at high velocity; their impact is within 2-5km away from the volcano.
    • They can travel further if the volcano is more explosive.

    Volcanic Gases

    • Before eruptions, gases build pressure inside magma and may be released.
    • Various volcanic gases (water vapor, carbon dioxide, sulfur dioxide, hydrogen sulfide, and halogens) are released.

    Lava Flows

    • Lava flows, in a bright red-orange appearance, are from released magma inside volcanoes.
    • Lava flow speed depends on silica content:
      • Low silica magma = low viscosity = high lava flow speeds
      • High silica magma = high viscosity = low lava flow speeds.
    • Lava flow impacts, with its high temperature, are capable of forest fires, burning vegetation, residential houses, and infrastructure.

    Signs of Impending Volcanic Eruptions

    • The Frequency of earthquakes increases.
    • The release of steam or gases from vents near the volcano increases (seen as a cloud afar).
    • Fumarolic activity increases, showing an increase in carbon dioxide concentration in the air.
    • The heat from magma close to the volcano's surface dramatically raises temperatures in the region.

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    This quiz explores various earthquake hazards such as ground shaking, ground rupture, liquefaction, and their impacts. You will learn about how these hazards affect structures and the environment. Test your knowledge on the causes and consequences of these seismic phenomena.

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