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Questions and Answers
What is the primary factor that distinguishes shield volcanoes from composite volcanoes?
What is the primary factor that distinguishes shield volcanoes from composite volcanoes?
Which feature is formed as a result of explosive eruptions that lead to a collapse?
Which feature is formed as a result of explosive eruptions that lead to a collapse?
What is the most significant sign of impending volcanic activity?
What is the most significant sign of impending volcanic activity?
Which type of lava is most commonly associated with volcanic activity?
Which type of lava is most commonly associated with volcanic activity?
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What was the initiating factor that triggered the blast of Mt. St. Helens?
What was the initiating factor that triggered the blast of Mt. St. Helens?
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What year did Hurricane Katrina occur?
What year did Hurricane Katrina occur?
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Which of the following is NOT a criterion for an event to be classified as a natural disaster?
Which of the following is NOT a criterion for an event to be classified as a natural disaster?
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What relationship exists between magnitude and frequency of natural hazards?
What relationship exists between magnitude and frequency of natural hazards?
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What primarily causes a tsunami to develop?
What primarily causes a tsunami to develop?
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At what speed can a tsunami move in the deep ocean?
At what speed can a tsunami move in the deep ocean?
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Which of the following factors does NOT contribute to the transformation of natural processes into hazards?
Which of the following factors does NOT contribute to the transformation of natural processes into hazards?
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What occurs to a tsunami as it approaches land?
What occurs to a tsunami as it approaches land?
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What is a defining characteristic of a catastrophe?
What is a defining characteristic of a catastrophe?
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Which of the following is not a way to minimize tsunami hazards?
Which of the following is not a way to minimize tsunami hazards?
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Which scenario represents an anticipatory human response to hazards?
Which scenario represents an anticipatory human response to hazards?
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In terms of damage from natural hazards, which is typically higher in developing countries?
In terms of damage from natural hazards, which is typically higher in developing countries?
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What does probability analysis relate to in terms of tsunami risk?
What does probability analysis relate to in terms of tsunami risk?
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If you are at the beach during a strong earthquake, what is the appropriate action to take?
If you are at the beach during a strong earthquake, what is the appropriate action to take?
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What does disaster forecasting represent?
What does disaster forecasting represent?
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What is the source of magma formation in the Earth?
What is the source of magma formation in the Earth?
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What is a characteristic of the Pacific Ring of Fire?
What is a characteristic of the Pacific Ring of Fire?
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What is the focus of an earthquake?
What is the focus of an earthquake?
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Which of the following directly triggers a tsunami?
Which of the following directly triggers a tsunami?
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What characterizes interplate earthquakes?
What characterizes interplate earthquakes?
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What type of seismic wave travels the slowest and causes the most damage?
What type of seismic wave travels the slowest and causes the most damage?
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What does amplification refer to in the context of earthquakes?
What does amplification refer to in the context of earthquakes?
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Which term describes the phenomenon when rupture propagation exceeds the speed of shear or surface waves?
Which term describes the phenomenon when rupture propagation exceeds the speed of shear or surface waves?
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In which of the following scenarios would intraplate earthquakes typically occur?
In which of the following scenarios would intraplate earthquakes typically occur?
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How is the moment magnitude scale primarily characterized?
How is the moment magnitude scale primarily characterized?
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Study Notes
Hurricane Katrina
- Occurred on August 29, 2005
- Severity exacerbated by regional subsidence, sea level rise, and geographic location
Natural Disasters
- Defined by:
- 10 or more people killed
- 100 or more people affected
- Emergency declaration issued or request for international assistance
Natural Hazards
- Become hazards due to:
- Human presence in vulnerable areas
- Urbanization and deforestation
- Construction on floodplains and earthquake-prone areas
- Energy consumption
- Climate change
Magnitude and Frequency of Natural Hazards
- Inverse relationship:
- Low magnitude and high frequency events are often less destructive.
- High magnitude events are destructive even if less frequent.
Mixed Blessings of Natural Hazards
- Benefits:
- Creation of new land
- Soil nutrient enrichment
- Removal of pollutants
- Landscape modification
- Formation of natural dams and water resources
Damage of Natural Hazards
- Developing countries:
- Higher life loss
- Developed countries:
- Higher property loss
Catastrophe
- A disaster requiring a long recovery process from damages.
Disaster Forecasting, Prediction, and Warning
-
Forecasting:
- Estimating the probability of an event occurring.
-
Prediction:
- Predicting the time, location, type, and size of an event.
-
Warning:
- Public notification based on a completed forecast or prediction.
Risk Assessment
- Risk threshold: The level of risk society is willing to accept.
- This involves balancing the probability and consequences of hazards.
Human Responses to Hazards
-
Reactive:
- Actions taken after a hazard event.
- Includes recovery phases, recovery period, needs assessment, essential functions, improvement, and development.
-
Anticipatory:
- Actions taken before a hazard event.
- Includes:
- Recognizing and avoiding hazards
- Minimizing impacts of disasters through preparedness activities
- Evacuation safety measures
- Disaster awareness
- Land-use planning
Earthquakes
- Violent ground shaking caused by the sudden release of strain energy stored in rocks.
- Measured using the Moment Magnitude Scale.
Human-Induced Earthquakes
- Can be triggered by:
- Reservoir construction
- Deep waste disposal
- Nuclear explosions
Earthquake Terminology
- Focus: The point beneath the Earth's surface where rocks rupture to generate an earthquake.
- Epicenter: The point on the Earth's surface directly above the focus.
- Moment Magnitude: A measure of an earthquake's strength based on energy released.
- Richter Magnitude: A measure of earthquake intensity based on the amplitude of seismic waves.
Earthquake Magnitude Scale
- The amount of energy released increases significantly with each unit increase in magnitude.
Earthquakes (Interplate and Intraplate)
- Interplate: Occur along plate boundaries.
-
Intraplate: Occur within plates, away from boundaries.
- Examples: New Madrid Seismic Zone, Charleston Earthquake
Types of Faults
- Normal Fault: Tensional forces pulling the Earth's crust apart.
- Reverse Fault: Compressional forces pushing the Earth's crust together.
- Thrust Fault: A type of reverse fault with a low-angle fault plane.
- Strike-Slip Fault: Lateral forces causing horizontal movement along the fault plane.
Seismic Waves
- P (Primary) waves: Compressional waves that travel the fastest through all physical states.
- S (Secondary) waves: Shear waves that travel slower than P waves but faster than surface waves, pass through solids only.
- Surface Waves: Travel along the Earth's surface, slowest waves but cause the most damage.
Material Amplification, Supershear, and Directivity
- Amplification: Ground shaking intensity is greater in unconsolidated materials (sediments, etc.).
- Supershear: Fault rupture propagates faster than the speed of shear or surface waves.
- Directivity: Shaking intensity increases in the direction of the fault rupture.
Tsunamis
- Japanese word for "large harbor waves," generated by sudden vertical displacement of ocean water.
- Triggers:
- Submarine earthquakes
- Landslides
- Volcanism
- Asteroid or comet impact
Megathrust Events
- Large displacement events along thrust faults in subduction zones.
Stages of Tsunami Formation
- Earthquake rupture: Uplifts the seafloor, triggering the tsunami.
- Wave propagation: Travels rapidly through the deep ocean, speeds exceeding 500 km/h.
- Wave transformation: Speed decreases to around 45 km/h near land, height increases.
- Inland inundation: Tsunami crashes onto land, inflicting significant damage
Local and Distant Tsunamis
- During a tsunami, the initial wave splits into a local tsunami impacting the nearby coastline and distant tsunamis affecting distant shores
Tsunami Risk Zones
- All ocean and some lake shorelines are at risk.
- Some coastlines are more vulnerable than others.
Minimizing Tsunami Hazards
- Detection and warning: Early detection and warning systems allow for evacuation.
- Structural control: Building structures to withstand tsunami forces.
- Tsunami Runup Maps: Mapping potential tsunami inundation zones.
- Land use planning: Restricting development in high-risk areas.
- Probability analysis: Assessing the likelihood of tsunamis occurring.
- Education: Public awareness and preparedness campaigns
Probability Analysis
- Risk: A calculated product of the probability of an event occurring and its potential consequences.
Adjustment to Tsunami Hazards
- Public safety recommendations:
- Leave the beach and low-lying coastal areas immediately if you feel a strong earthquake.
- Recognize that the ocean receding is a warning sign of an approaching tsunami.
- Understand that tsunamis may be smaller in one location but larger in other nearby locations.
- Recognize that a tsunami may consist of a series of waves and stay out of dangerous areas until further notice.
- Familiarize yourself with warning sirens and evacuation routes.
- Move to higher ground, at least 20m (60ft) above sea level.
- Stay informed about tsunami watches or warnings and don't go near the beach to observe the waves.
Volcanism
- Volcanic activity is directly linked to plate tectonics.
- Most active volcanoes are located near plate boundaries.
- The Pacific Ring of Fire concentrates two-thirds of active volcanoes.
Formation of Magma
- Source: The asthenosphere.
-
Conditions for melting:
- Temperature increase with depth.
- Decompression melting: Pressure on hot rocks decreases.
- Addition of volatiles: Lowers the melting point of rocks.
Types of Volcanoes
- Shield Volcano: Gentle slopes, basaltic lava flows.
- Composite Volcano: Cone-shaped, explosive activity and lava flows.
- Volcanic Domes: Viscous magma, high silica content, rhyolite is a common rock type.
- Cinder Cones: Small cones formed from tephra (volcanic ash, volcanic bombs)
Viscosity
- A liquid's resistance to flow.
Volcanic Features
- Craters: Bowl-shaped depressions at the summit of a volcano.
- Vents: Openings in the Earth's crust through which magma erupts.
- Volcanic Cones: Conical structures formed by volcanic eruptions.
- Calderas: Collapsed craters, often resulting from explosive eruptions.
- Hot Springs and Geysers: Geothermal features where heated water reaches the surface.
- Fissure Lines: Cracks in the Earth's surface where lava flows.
Case Study: Mount St. Helens
- Eruption initiated by:
- An earthquake of ~4-5 magnitude
- Triggered landslide displaced water in Spirit Lake
Forecasting Volcanic Activity
-
Monitoring techniques:
- Seismic activity: Increased earthquake frequency and intensity.
- Thermal, magnetic, and hydrologic conditions: Changes in heat flow, magnetic field, and groundwater levels.
- Gas emission: Increased volume and changes in composition of gases.
- Topographic monitoring: Tilting and ground swelling.
- Remote sensing: Radar and 3D interferometry to detect changes in surface elevation.
- Geological history: Analyzing past eruption patterns.
Lava Flows
- Most common: Basaltic lava, low viscosity.
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Description
Explore the significant factors, definitions, and impacts surrounding natural disasters with a focus on Hurricane Katrina. This quiz covers topics like the causes of natural hazards and their mixed blessings, providing insights into both the destructive and beneficial aspects of these events.
