Hazards Flashcards
What is a Hazard?
A potential threat to human life and property caused by an event.
Becomes a hazard when it poses a threat to people.
What is a Disaster?
The result of a hazard occurring with loss of life and damage to the built and natural environment.
What are the characteristics of hazards?
- Clear origins and effects
- Short warning times
- Involuntary exposure
- Most loss occurs immediately after the event
- Requires emergency response
What are the three types of Natural Hazards?
GEOPHYSICAL- Hazards caused by land processes i.e. earthquakes and volcanos
ATMOSPHERIC- Caused by atmospheric processes i.e. tropical storms and wildfires
HYDROLOGICAL- Caused by water bodies and movements like tsunamis and floods
What’s the difference between risk and vulnerability?
Risk- The exposure of people to a hazard presenting a possible threat to life, possessions, and the built environment.
Vulnerability- The potential for loss of life and possessions, varying between social groups, locations, and timescales.
Why do people live in hazard- prone areas?
- Low perceived risk
- Lack of alternatives
- Risk levels change over time
-Benefits outweigh costs - Family history
- Tourism income
- Scenic views
- Volcanic soil is fertile
What are the three hazard perception approaches?
Fatalism: Accepting hazards as natural events beyond control
Adaptation: Preparing effectively to survive events
Fear: Feeling too vulnerable to live in the area
What are the factors influencing hazard perception?
- Socio-economic status
- Level of education
- Occupational status
- Religion and cultural background
- Family and marital status
- Past experience
- Values and expectations
- Geographical stats
What are the three methods of hazard management?
Prediction: Warnings through monitoring systems
Prevention: Often unrealistic (e.g., stopping tropical storms)
Protection: Modifications to built environments (e.g., sea walls)
What is integrated risk management?
process considering all factors (social, economic and political) involved in risk management. This determines the acceptability of damage and disruption and deciding the actions to reduce and mitigate this.
What are the steps in integrated risk management?
- Identification
- Analysis of risks
- Establishing priorities
- Risk reduction
- Public awareness
- Monitoring and reviewing
Give examples of successful hazard management
Mt. Etna: Used dynamite to divert lava flows
Iceland (1978): Used dynamite to prevent lava cutting off the harbor
Give examples of unsuccessful hazard management
Japan (1995): Great Hanshin Earthquake destroyed 10,000+ buildings despite preparation
What are the steps in the hazard management cycle?
Preparedness: Education, risk assessment
Response: Immediate actions (rescue, warning, evacuation)
Recovery: Short- and long-term restoration
Mitigation: Future impact reduction via defenses & infrastructure
What does the park model show?
Illustrates hazard impact on quality of life over time
Influencing factors: Hazard type, intensity, infrastructure, economic status
Possible improvements post-event: Better infrastructure, awareness, investment, emergency aid
What are the key hazard characteristics?
Distribution: Spatial coverage (area or location affected)
Frequency: How often hazards occur
Magnitude: Size and impact of the hazard
What is the shape of the Earth called and why?
The Earth is a geoid, meaning it bulges at the equator and flattens at the poles due to centrifugal forces.
What are the four main layers of the Earth?
Crust, Mantle, Outer Core, Inner Core.
What is the difference between the inner and outer core?
The inner core is solid (iron/nickel) due to high pressure, while the outer core is semi-molten.
What are the two types of crust and their characteristics?
Continental crust: Thick (30-70 km), Old (1.5 billion years), Low Density, Made of SIAL (Granite).
Oceanic crust: Thin (6-10 km), Young (200 million years), High Density, Made of SIMA (Basalt).
What are the two sources of heat inside the Earth?
Primordial heat (leftover from Earth’s formation)
Radiogenic heat (from radioactive decay).
What is the lithosphere and how does it interact with the asthenosphere?
The lithosphere is broken into tectonic plates, which move on the semi-molten asthenosphere due to convection currents.
Who proposed the Continental Drift Theory, and what was the key evidence?
Alfred Wegener (1912) proposed that continents were once a single landmass (Pangaea). Evidence includes:
- Fit of the coastlines (e.g., South America & Africa)
- Fossil correlation (e.g., Mesosaurus found in Africa & South America)
- Geological correlation (similar rock formations across continents)
- Paleo-climate data (e.g., glacial deposits in warm regions)
How did sea-floor spreading support plate tectonic theory?
Discovery of the Mid-Atlantic Ridge and:
- Age of Rocks: Youngest in the center, older outward.
- Magnetic Reversals: Alternating bands of rock show changes in Earth’s polarity every 400,000 years.
What are convection currents, and how do they drive plate movement?
Hot magma rises, spreads, cools, and sinks, creating movement that drags tectonic plates.
What is ridge push (gravitational sliding)?
Magma rising at mid-ocean ridges pushes plates apart due to gravity
What is slab pull?
At destructive margins, the denser oceanic plate subducts, pulling the rest of the plate with it.
What happens at a constructive boundary?
Two plates move apart, creating new crust from rising magma.
What landforms are associated with constructive boundaries?
Oceanic Setting: Mid-ocean ridges (e.g., Mid-Atlantic Ridge).
Continental Setting: Rift valleys (e.g., East African Rift Valley).
What are the three types of destructive plate interactions?
Oceanic vs. Continental: Subduction forms deep-sea trenches (e.g., Mariana Trench) and volcanoes.
Oceanic vs. Oceanic: The denser plate subducts, forming island arcs (e.g., Japan).
Continental vs. Continental: Plates collide, creating fold mountains (e.g., Himalayas).
What is the Benioff Zone?
The area in a subduction zone where the oceanic plate melts, causing earthquakes and volcanic activity.
What happens at a conservative boundary?
Plates slide past each other, causing earthquakes but no volcanic activity (e.g., San Andreas Fault).
What are magma plumes and how do they relate to plate movement?
Rising columns of hot magma create volcanic hotspots (e.g., Hawaii). As plates move, old volcanoes become extinct, and new ones form.
Where are volcanoes most commonly found?
At plate boundaries, especially constructive and destructive margins. Also in high-activity areas like the Ring of Fire and at hotspots (e.g., Hawaii).
What scale is used to measure volcanic explosivity?
The Volcanic Explosivity Index (VEI), a logarithmic scale from VEI 2 onwards, considering tephra volume, eruption duration, and plume height.
How do scientists determine eruption frequency?
By studying historical records, deposited materials, and ice cores.
What are the three classifications of volcanoes?
Active (frequently erupting), Dormant (inactive but could erupt), Extinct (unlikely to erupt).
Talk about Icelandic eruption style
The least explosive where lava flows gently and slowly allowing it to cool and condense and form new land
effusive
Talk about the Hawaiian eruption style
Still slow moving lava but a bit more explosive than Icelandic. Usually occurs on hotspots with the lava cooling and condensing when it hits water. This usually makes a dome shaped volcano. effusive
Talk about the strombolian eruption style?
These are frequent, explosive volcanoes with lava bombs, tephra and steam explosions and occasional short lava flows. Here ash clouds are more noticeable than the other two
Talk about the vulcanian eruption style.
Less frequent but more violent with large amounts of gas, ash and tephra released. They are known as having a sustained ash cloud column, pyroclastic flows and volcanic bombs.
Talk about the Plinian eruption style
Extremely violent eruptions with big ash and gas clouds, pumice bombs, torrential rainstorms and devastating lahars.
What is tephra?
Solid materials ejected into the air during an eruption.
What are pyroclastic flows?
Fast-moving, 800°C, high-velocity flows of gas and tephra, moving up to 700 km/h.
What are the two types of lava flows?
Pahoehoe - Smooth and gloopy
Aa - Rough and jagged
Name four volcanic gases released during eruptions.
CO₂, Carbon monoxide, Chlorine, Sulphur dioxide.
How does acid rain form from volcanic eruptions?
Sulphur dioxide mixes with atmospheric moisture, causing acidic precipitation.
Give examples of social impacts of a volcanic eruption.
People killed, homes destroyed, Fires can start, mudflows, floods, trauma, homelessness
Give examples of environmental impacts of a volcanic eruption.
Ecosystems damaged through varous hazards, wildlife killed, Water acidified by acid rain, volcanic gases contribute to greenhouse gas effect.
Give examples of economic impacts of a volcanic eruption.
Businesses and indistires destroyed or disrupted, Jobs lost, profit from tourism industry after
Give examples of Short term responses of volcanoes
Financial aid food and water. temporary infrastructure early. alert alarm systems. Troops and Navy aid. exclusion zones. Evacuation
Give examples of long- term responses
Long term financial aid redevelopment permanent migration. mitigation infrastructure.
Why is it difficult to predict volcanic eruptions?
Volcanoes do not always show clear warning signs, and prediction is not 100% accurate
Name four ways scientists monitor volcanic activity.
Ground deformation (e.g., bulging of land).
Gas emissions (increase in sulphur dioxide).
Seismic activity (more earthquakes).
Changes in groundwater temperature.
