Geological Hazards: Landslide Quiz
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Questions and Answers

What natural phenomenon can occur when groundwater abstraction creates a cavity?

  • Earthquake
  • Sinkhole (correct)
  • Landslide
  • Flood
  • Which factor contributes to ground subsidence during the dry season in areas with clay soil?

  • Soil expansion
  • Increased water levels
  • Soil saturation
  • Soil shrinkage (correct)
  • How does oil and natural gas extraction affect rock layers?

  • Weakens the pressure supporting rock layers (correct)
  • Adds more voids to the layers
  • Increases pressure between layers
  • Creates new underground reservoirs
  • What is the typical wind speed classification of a typhoon?

    <p>118-220 kilometers per hour (D)</p> Signup and view all the answers

    What happens to the pressure between rock layers due to groundwater withdrawal?

    <p>It lessens and can lead to subsidence (C)</p> Signup and view all the answers

    What are the signs that indicate a typhoon is close to landfall?

    <p>Increased ocean swell (A)</p> Signup and view all the answers

    Which process is a common natural cause of ground subsidence?

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

    What role do underground mining activities play in ground subsidence?

    <p>They displace large amounts of material (C)</p> Signup and view all the answers

    Which factor contributes to oversteepening of a slope?

    <p>Excavation of the base of the slope (D)</p> Signup and view all the answers

    What process leads to the formation of a void underground when limestone is involved?

    <p>Dissolution of calcite by acidic water (D)</p> Signup and view all the answers

    Which geological hazard is described as settling of the earth's surface below its natural level over time?

    <p>Ground subsidence (A)</p> Signup and view all the answers

    What effect does adding a landfill or construction on top of a slope typically have?

    <p>Increases the risk of landslides (A)</p> Signup and view all the answers

    Which natural process is a primary contributor to ground subsidence?

    <p>Carbonate dissolution in limestone regions (C)</p> Signup and view all the answers

    What creates acidic water that can dissolve limestone?

    <p>Combination of carbon dioxide with water vapor (B)</p> Signup and view all the answers

    What is the consequence of acidic water reacting with limestone underground?

    <p>Creation of voids leading to subsidence (D)</p> Signup and view all the answers

    Which of the following is a characteristic of geological hazards?

    <p>They can disrupt economic and social activities (A)</p> Signup and view all the answers

    What is a common result of an incoming typhoon?

    <p>A swell of about a meter every 10 seconds (D)</p> Signup and view all the answers

    Which cloud type typically fills the sky about 36 hours before a typhoon?

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

    What indicates that a thunderstorm may be developing?

    <p>Cumulonimbus clouds forming (C)</p> Signup and view all the answers

    What is one of the impending signs of a thunderstorm?

    <p>The sky turns dark (D)</p> Signup and view all the answers

    What happens to atmospheric pressure as a typhoon approaches?

    <p>It drops significantly (B)</p> Signup and view all the answers

    What might signify a severe thunderstorm in terms of wind conditions?

    <p>Sudden gusts of wind and shifting wind direction (D)</p> Signup and view all the answers

    What can happen if a thunderstorm becomes severe?

    <p>It may lead to heavy rainfall and strong winds. (D)</p> Signup and view all the answers

    Which of the following is NOT typically associated with an approaching typhoon?

    <p>A clear sky with no wind (C)</p> Signup and view all the answers

    Which factor is a natural cause of landslides?

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

    What is the primary reason for slope failure in oversteepening?

    <p>Increase in the slope angle (B)</p> Signup and view all the answers

    How does vegetation contribute to slope stability?

    <p>Balances the slope load (A)</p> Signup and view all the answers

    What might artificially increase the risk of landslides on a slope?

    <p>Constructing infrastructures (C)</p> Signup and view all the answers

    What is one effect of prolonged heavy rainfall on slopes?

    <p>Weakens soil hold on the slope (D)</p> Signup and view all the answers

    Which process may lead to overloading of a slope?

    <p>Excavating the base of the slope (C)</p> Signup and view all the answers

    How does human activity typically contribute to landslides?

    <p>By increasing vibrations on slopes (D)</p> Signup and view all the answers

    Which of the following is NOT a cause of landslides?

    <p>Planting vegetation (D)</p> Signup and view all the answers

    Which scenario illustrates natural landslide oversteepening?

    <p>Erosion of the slope's base due to rain (D)</p> Signup and view all the answers

    What role does slope angle play in stability?

    <p>Steeper angles may lead to slope failure (D)</p> Signup and view all the answers

    What are the three primary elements needed to sustain a fire?

    <p>Oxygen, heat, fuel (A)</p> Signup and view all the answers

    During which stage of a fire is it considered to be at its hottest point?

    <p>Fully Developed (D)</p> Signup and view all the answers

    What is a common cause of fires related to electrical systems?

    <p>Faulty electrical wiring (C)</p> Signup and view all the answers

    Which of the following is considered a dangerous stage of fire, even when it is running out of fuel?

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

    Which of the following types of fires can be caused by unattended open flames?

    <p>Matchstick or lighter near flammable materials (A)</p> Signup and view all the answers

    What is the primary function of a barograph?

    <p>To continuously record atmospheric pressure (C)</p> Signup and view all the answers

    Which instrument is used to measure the height of the cloud base using time measurement?

    <p>Ceiling balloon (A)</p> Signup and view all the answers

    What does a rawinsonde measure in addition to temperature and pressure?

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

    How does Weather Surveillance Radar function?

    <p>By detecting and monitoring the track of weather events (B)</p> Signup and view all the answers

    Which color indicates a low susceptibility to landslides in rain-induced areas?

    <p>Yellow (C)</p> Signup and view all the answers

    Which instrument uses radar echoes to determine wind speed and direction?

    <p>Wind finding radar (B)</p> Signup and view all the answers

    What does Doppler Radar primarily estimate?

    <p>Type and motion of precipitation (A)</p> Signup and view all the answers

    Which weather monitoring tool is equipped with a transmitter for atmospheric measurements?

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

    Flashcards

    Landslide Causes

    Landslides occur when soil and rock move downhill due to gravity.

    Landslide Cause - Natural

    Natural causes include steep slopes, soil types, water, earthquakes, and volcanic eruptions

    Landslide Cause - Artificial

    Human activities like deforestation, building, mining, and vibrations can trigger landslides.

    Slope Stability

    A stable slope means soil and rock remain in place; instability leads to landslides.

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    Oversteepening

    Reducing the base of a slope, like cutting or excavating, making it unstable.

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    Overloading

    Adding weight to a slope—buildings, landfills, water—increasing the risk of landslides

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    Overloading (Water)

    Water increases a slope's weight and weakens the soil. Excessive rain can saturate the ground.

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    Vegetation Role

    Vegetation helps manage water, stabilizing slopes by reducing erosion and balancing the load.

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    Deforestation Impact

    Removing vegetation increases the risk of landslides, as it removes stabilizing factors.

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    Ground Subsidence

    The gradual settling or sinking of the ground surface due to loss of support.

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    Groundwater Abstraction

    Withdrawal of groundwater from an aquifer, which can lead to the ground sinking.

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    Sinkhole Formation

    A sudden collapse of the ground surface, often formed from a cavity dissolving beneath the ground.

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    Typhoon

    A violent tropical cyclone occurring in the western Pacific Ocean north of the equator.

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    Tropical Cyclone

    A rotating weather system with low-pressure center, wind and precipitation.

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    Ocean Swell

    Series of ocean waves created by strong winds, a tell-tale sign of a approaching storm.

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    Ground subsidence due to mining

    The ground sinking due to removal or displacement of underground materials.

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    Ground subsidence in seasonal changes

    Ground sinking due to the drying of clay soil.

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    Typhoon Swell

    The rise in ocean water level caused by a typhoon, typically reaching about a meter in height and hitting the shore every 10 seconds.

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    Landslide Cause: Oversteepening

    Landslides can happen when the slope becomes too steep due to factors like weathering or excavation at the base.

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    Landslide Cause: Overloading

    A landslide can occur when extra weight is added to a slope, such as building construction, or leaking water sources

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    Typhoon Approach: Wave Changes

    As a typhoon gets closer, the waves become larger and arrive more frequently, indicating an increase in intensity.

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    Typhoon Warning: Cumulus Clouds

    Cumulus clouds filling the sky about 36 hours before a typhoon signals its potential arrival.

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    Typhoon Precursor: Cirrus Clouds

    A veil-like layer of cirrus clouds appearing on the horizon indicates a typhoon may be approaching.

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    Ground Subsidence Cause: Carbonate Dissolution

    Ground subsiding due to slow natural process of dissolving carbonate-rich rocks like limestone by acidic water caused by CO2.

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    Typhoon Sign: Barometric Pressure Drop

    A significant drop in atmospheric pressure, starting around 36 hours before a typhoon, is a key indicator.

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    Geological Hazard

    Naturally occurring events potentially dangerous to people, infrastructure and environment.

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    Thunderstorm: Cumulonimbus Clouds

    Large, towering Cumulonimbus clouds signal the formation of a thunderstorm. They are formed by rising, moist air.

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    Limestone Dissolution

    The process of dissolving limestone by acidic water. Creating voids or empty spaces.

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    Ground Subsidence: Cavity Formation

    Underground erosion of rocks and soil creates voids or cavities, hence causing ground subsidence.

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    Thunderstorm Warning: Darkening Sky

    The sky turns dark due to thick, water-laden Cumulonimbus clouds, indicating an approaching thunderstorm.

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    Thunderstorm Sign: Lightning & Thunder

    Flashes of lightning accompanied by thunder are a clear indication of a thunderstorm, even before rainfall.

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    Acidic Water Formation

    Carbon dioxide (CO2) in the atmosphere combining with water vapor (H2O) to form carbonic acid (H2CO3), eventually falling as acid rain.

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    Fire Triangle

    The three essential components needed for fire to start and sustain itself: heat, fuel, and oxygen.

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    Incipient Stage of Fire

    The initial stage of fire where ignition occurs, but the fire is still small and hasn't spread significantly.

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    Fully Developed Fire

    The most intense stage of fire where it reaches its highest temperature and burns all available fuel.

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    Decay Stage of Fire

    The final stage of fire where the fuel begins to run out, and the fire slowly diminishes.

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    Causes of Fires

    A wide range of factors that can lead to a fire, including electrical faults, unattended flames, flammable substances, and human negligence.

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    Barograph

    A device that continuously records atmospheric pressure changes.

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    Thermograph

    An instrument that continuously measures and records air temperature.

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    Ceiling Light Projector

    Projects a light beam onto clouds to determine cloud base height.

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    Clinometer

    Measures the angle between the ground and the cloud base to determine cloud height.

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    Ceiling Balloon

    A balloon filled with gas lighter than air, released to determine cloud base height by measuring time to disappear into clouds.

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    Theodolite

    An instrument that determines wind speed and direction by tracking a hydrogen-filled balloon.

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    Radiosonde

    An instrument attached to a balloon that measures temperature, pressure, and humidity in the atmosphere.

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    Rawinsonde

    Similar to a radiosonde, but also measures wind velocity.

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    Study Notes

    Geological Hazards

    • Naturally occurring earth phenomena that can cause danger and disrupt economic and social activities.
    • Examples include landslides and ground subsidence.

    Landslide

    • Downslope bulk displacement of soils and rocks due to gravity.
    • Natural Causes:
      • Weathering
      • Slope angle (steepness)
      • Soil profile and its components
      • Groundwater activity
      • Earthquakes
      • Volcanic eruptions
      • Extreme rainfall
    • Artificial Causes:
      • Deforestation
      • Adding weight to slopes (buildings, infrastructure)
      • Vibrations (traffic, human activity)
      • Mining
      • Quarrying
    • Slope Stability and Equilibrium:
      • Slope stability depends on slope angle, slope's load, and slope equilibrium.
      • Failure to achieve equilibrium is caused by increased slope angle (oversteepening) and increased slope load (overloading).
    • Oversteepening:
      • Happens when a part of a slope is cut, excavated or eroded.
      • Happens naturally due to weathering or artificially.
      • Weakens the support of the slope's lower section/base on its load.

    Ground Subsidence

    • Settling or subsiding of Earth's surface below the natural ground surface level.
    • Occurs over a long period.
    • Less dangerous than other hazards.
    • Carbonate Dissolution and Collapse:
      • Slow natural process causing ground subsidence.
      • Common in limestone areas.
      • Limestone is mainly calcium carbonate.
      • Acidic water dissolves limestone, creating voids underground.
      • The voids can cause depressions on the surface, potentially creating sinkholes.

    Ground Subsidence: Causes

    • Groundwater Abstraction:
      • Withdrawal of water from underground sources reduces pressure between rock layers.
      • This can cause surface depression ("subsidence").
    • Underground Mining:
      • Removal of large amounts of underground material can cause subsidence.
    • Change of Season:
      • Dry seasons cause clay soil to shrink, leading to ground subsidence in areas with abundant clay.
    • Oil and Natural gas extraction:
      • The process reduces the pressure between layers, weakening support systems for upper layers.

    Hydrometeorological Hazards

    • Typhoons:
      • Violent tropical cyclones over warm waters (North of equator, Western Pacific Ocean).
      • Counterclockwise winds (speed 118-220 km/h; super typhoons >220km/h).
      • Signs include increased ocean swell, changes in clouds (cirrus, dark clouds), barometric pressure drop, and abrupt changes in wind speed.
    • Thunderstorms:
      • Small-scale storms with lightning and thunder.
      • Usually last 30 min. to an hour.
      • Potential hazards include strong winds and heavy rainfall (hail, tornadoes).
      • Signs include a system of cumulonimbus clouds, dark sky (with tints), lightning and thunder.

    Flood and Flash floods

    • Flooding occurs when land areas are submerged, often after heavy rainfall.
    • Flash floods occur faster, often due to heavy rainfall on already saturated ground.
    • Signs of flooding include standing water, rapidly rising water, muddy water, and debris in water.

    Fire

    • The elements of fire triangle: Oxygen, heat and fuel.
    • Stages of fire: Incipient, growth, fully developed, and decay.
    • Causes of fires: Faulty wiring, gas leaks, neglected stoves/appliances, and cigarettes.

    Tools for monitoring

    • Mention various instruments and tools used to monitor different weather conditions including typhoons, floods, and fires to prevent potential hazards or predict the hazard occurrence.

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    Related Documents

    Geological Hazards PDF

    Description

    Test your knowledge on geological hazards, focusing specifically on landslides. Explore the natural and artificial causes, as well as principles of slope stability and equilibrium. Understand how various factors influence the occurrence of this natural phenomenon.

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