Challenge of Natural Hazards Flashcards
Natural Hazards, Tectonic Hazards, Weather Hazards, Climate Change
Natural Hazard: A threat…
A threat (whether natural or human) that has the potential to cause loss of life, property damage, injury, socio-economic disruption or environmental degradation. (eg, Hurricane Haiyan, Mt St Helen eruption)
Tectonic hazards (caused by movement of plates)
Earthquakes, volcanoes, tsunamis
Biological hazards (involves living organisms)
Forest fires
Atmospherical hazards (caused by changes in the atmosphere)
Tropical storms, blizzards, tornadoes
Geomorphic hazards (occurs on the earth’s surface)
Floods, landslides (can also trigger other natural events)
Hazard risk (factors that affect response)
- Experience
- Education
- Material well-being (wealth)
- Personality
- Age — children, elderly, pregnant women
- Personality (leader/follower)
- Emergency response
- Infrastructure
Hazard risk (why people live near areas with tectonic activity)
- Fertile soils —> successful farming
- No choice —> poverty (no other options)
- Economic activity (rich in resources, tourism growing in volcanic areas)
- Perception of risk —> natural hazards are rare and moving away is too much of a struggle
- Investment —> developed cities in HICs (eg, Los Angeles) have earthquake proof buildings
- Early warning systems —> satellites and technology can detect the arrival of a natural hazard
- Geographical inertia —> families lived here, coupled with rapid population growth in LEDCs
- Hazard management —> technology and infrastructure designed to have less impact from natural hazards
Key factors affecting hazard risk
- Vulnerability
- Population density — (higher population density, more -people are vulnerable)
- Capacity to cope — (HICs often better equipped - build defenses, evacuate quickly, quick emergency response, swift medical assistance, rebuild quickly)
- Level of preparation
- Hazard type — (some can be predicted - tropical storms - others cannot - earthquakes)
- Hazard frequency — (many earthquakes make it hard to rebuild quickly and great damage to economy)
- Nature — (more severe natural hazards cause greater impacts)
Tectonic hazards occur…
Tectonic hazards occur on or near plate margins, near the Pacific Ring of Fire, near coastal areas, the western coastline of North and South America, and south and eastern Asia
Layers of the earth: The Crust
- 80-40 km thick, less than 1% of the earth
- Composed of igneous, sedimentary and metamorphic rock
- Divided into tectonic plates —> destructive and constructive plates (oceanic and continental plates)
Layers of the earth: The Mantle
- 2900 km thick, 84% of the earth
- Composed of magma
- 500-900ºC
- Convection currents cause the plates in the crust to move
Layers of the earth: The Outer Core
- 2300 km, 15% of the earth
- Composed of iron and nickel
- 4000-5000ºC
Layers of the earth: The Inner Core
- (Radius) 1220 km, less than 1% of the earth
- Composed of iron and nickel, high pressure causes iron and nickel to remain solid
- 5000-7000ºC
Oceanic Crust is…
thin and more dense
Continental Crust is…
thick and less dense
Destructive Plate Margin
Plates move towards each other
Oceanic plate — Continental plate
Oceanic plate (more dense) subducts under Continental plate (less dense); oceanic plate melts and pressure builds from friction between two plates; eg, Andes
Earthquakes and Volcanoes occur
Collision Plate Margin
Plates move towards each other
Continental plate — Continental plate
No subduction occurs; plates of equal density crumple up to create fold mountains; eg, Himalayas
Earthquakes occur
Conservative Plate Margin
Plates move alongside each other
Plates can move in opposite directions or same direction at different speeds; pressure builds over a long period of time; eg, San Andreas Fault (same direction, different speeds)
Earthquakes occur
Constructive Plate Margin
Plates move apart
Gap created where magma rises; creates new oceanic floor or volcanic islands; eg, Iceland, Mid-Atlantic Ridge
Earthquakes and Volcanoes occur
Primary Effects
First/direct impact of a natural hazard on the population (people and property)
Secondary Effects
After effects of a natural hazard on a longer timescale
Immediate Response
How people react as the event is happening
Long-Term Response
How people react in the days/weeks/months after the event has happened
HIC
High income country — GNI is over $12,000 per person
LIC
Low income country — GNI is under $12,000 per person
Planning
Food & medical supplies; Evacuation center; Land use zoning; Education —> earthquake drills, TV adverts; Emergency & first aid kits; Good communication systems
Protection
Earthquake proof buildings (braces, pendulum, bolting houses to foundations, fire-resistant material, planning regulation appropriate);
Open areas;
Insurance (homes and businesses)
Prediction
Seismology (seismographs to measure foreshocks and tremors);
Animals behave strangely before;
Special monitors on cell phones
Monitoring
Seismometers; Thermal imaging; Volcano observatory; Gas samples to measure sulfur levels; Monitor radon gas levels; Groundwater level changes; Satellites
Cells
Polar cell Ferrel cell (60º) Hadley cell (30º) ——————————EQUATOR (0º)—————————— Hadley cell (30º) Ferrel cell (60º) Polar cell
Trade winds
Polar easterlies
North east
Polar easterlies
Pressure in cells
EQUATOR - HADLEY CELL ^^^ low pressure ^^^ —> precipitation, humid, hot, cloudy, (tropical rainforests)
HADLEY CELL - FERREL CELL ! ! ! high pressure ! ! ! —> desert, few clouds, hot at day (lots of insolation), cold at night, (deserts)
FERREL CELL - POLAR CELL ^^^ low pressure ^^^ —> precipitation
POLAR CAP ^^^ high pressure ^^^ —> desert
Insolation
Equator receives the most insolation (solar radiation hitting earth’s surface), less insolation at higher altitudes
Pressure System
Heated air expands and rises (it is less dense); there is low pressure.
Cooler air falls (it is more dense); there is high pressure.
Trade winds are caused by the Coriolis effect (rotation of the earth). They curve towards areas of low pressure from areas of high pressure. They transfer heat and moisture.
Seasonal changes
Tilt of the earth and rotation are responsible for seasonal changes
Global distribution of tropical storms
Occur in the tropics, away from the Equator —> they need to feel the Coriolis effect;
More tropical storms occur in the northern hemisphere
5º-20º N/S of the Equator;
Occur along the INTER TROPICAL CONVERGENT ZONE where the trade winds converge;
In the North, the trade winds push tropical storms to the West;
In the South, the trade winds push tropical storms to the East
Structure of a tropical storm
^ # ! 0 ! # ^ #
Warm air rises from ocean to form rain clouds
Eye has high pressure, air is falling
Formation of tropical storms
- Develop in warm oceans, exceeding 27ºC, and in depths of 70 m
- Air over warm, tropical oceans is heated, the warm air rises, in low pressure conditions
- As warm air rises, it brings more air with it and moisture from the evaporating ocean, resulting in strong winds
- Coriolis effect - air spins around a calm center
- The evaporated moisture condenses as it moves upwards and cools
- This causes more moisture to be drawn up
- Large volumes of condensed moisture from cumulonimbus clouds with heavy torrential rainfall
- Eye of the storm forms as cold air sinks - dry and calm
- Trade winds move it towards land, where it stops gaining energy
Weather of a tropical storm (with structure)
First 20-30 km: pressure falls; 100 km/h winds; cumulonimbus clouds; torrential rain; 250 mm rainfall/day; generally stormy.
Eye: 30-50 km; very low pressure; high temperature; sunny; generally calm.
Last 20-30 km: pressure rises; 160 km/h winds; torrential rain; temperature drops; generally violent.
Saffir-Simpson Scale
Category 1: 119-153 km/h winds; Category 2: 134-177 km/h winds; Category 3: 178-208 km/h winds; Category 4: 209-251 km/h winds; Category 5: 251 km/h + winds
Climate change affecting tropical storms
- More intense, not more frequent
- Location extends further N and S of the Equator —> more ocean is warmed up from enhanced greenhouse effect
- Vulnerability of low-lying coastal communities in the tropics increases —> rising sea level leads to flooding; places with high population density and income is low
- Warmer oceans —> more energy of storms —> higher storm surges
Extreme weather in the UK: Thunderstorms
Heavy rain, lightning, strong winds; lightning can cause deaths and fires, which damage property
Extreme weather in the UK: Rain
Too much in a short period of time can cause flooding, which puts people, property, businesses and the environment at risk. It can disrupt transport networks, destroy communication lines, cause drownings, and may cost millions of pounds to recover
Extreme weather in the UK: Snow and ice
May cause injuries from slipping or deaths due to cold. Schools and businesses may be forced to close, and crops may be ruined
Extreme weather in the UK: Hailstorm
This can damage crops, property and make driving dangerous
Extreme weather in the UK: Wind
Can uproot trees, destroy property (eg, ripping roofs off). Flying debris can kill. Forests may be damaged when trees are blown over
Extreme weather in the UK: Drought
Water supplies are low, leading to crop failure. Rules may be imposed to conserve water (eg, hosepipe ban)
Extreme weather in the UK: Heatwaves
Can cause deaths from breathing difficulties or heat exhaustion. Roads can melt, which disrupts transport, but tourism may benefit
Evidence for Climate Change: Global Temperature
Global temperatures have increased since the Industrial Revolution —> more thermometers now than in the past, but still reliable
Evidence for Climate Change: Ice Cores
Air bubbles in ice cores from the past tell us the different types of gases at that time —> carbon dioxide and methane levels. —> does not tell us the exact date and year, only an estimate
Evidence for Climate Change: Ocean Sediment
Organisms and remains of plankton tell us the past surface water temperatures, and levels of oxygen and nutrients. The deeper the sediment, the older it is. —> does not tell us the exact date and year, only an estimate
Evidence for Climate Change: Fossils
Fossils from the past tell us the required diet and habitat based on their size and characteristics. The data can be compared with animals today to understand if there was a different climate in the past —> does not tell us the exact date and year, only an estimate
Evidence for Climate Change: Tree Rings
A new ring forms every year around a tree. Tree rings are thicker when the climate is warm and wet. —> does not give a precise reading
Era
Living in the holocene epoch, in the quaternary period, in the Cenozoic era. Epoch begins when last glacial episode ended and current interglacial episode began.
(Natural) Causes of Climate Change: Eruption Theory
Large, explosive volcanic eruption release lots of ash into the atmosphere, blocking out sunlight and decreasing global temperatures. Sulfur dioxide is also released —> crop yields are disrupted and harvests fail, people can die
(Natural) Causes of Climate Change: Sunspot Theory
Many sunspots = sun is more active and emits more solar radiation, increasing global temperatures. 11 year cycle, activity decreases as years progress in cycle —> more droughts
(Natural) Causes of Climate Change: Asteroid Collision
Asteroid hitting earth throws up millions of tonnes of dust and ash in the atmosphere, blocking sunlight and decreasing global temperatures. Can last several years, depending on size of asteroid —> Decreases plant life, causing the death of consumers up in the food chain, causing death to many organisms
(Natural) Causes of Climate Change: Orbital Theory
Orbit of earth changes from more circular to more ellipse. Shorter distance between earth and sun, increase in global temperatures. The more tilted the earth is to the sun, increase in global temperatures. If it wobbles, temperatures fluctuate —> causes climate change worldwide (droughts, ice ages, glacial and interglacial episodes)
(Human) Causes of Climate Change: Deforestation
Making more land available for cattle ranching, agribusinesses, housing and urbanization. Slash and burn method to remove trees —> emits lots of CO2 (300 billion tonnes
(Human) Causes of Climate Change: Fossil Fuels
Coal, oil, natural gas burned for heat and energy. Used for fuel for vehicles, generate electricity, and manufacture plastic. CO2 released, increasing CO2 concentration in the atmosphere, enhancing greenhouse effect.
(Human) Causes of Climate Change: Agriculture
Deforestation used —> slash and burn technique, releasing CO2 in atmosphere, enhancing greenhouse effect. Methane released from cattle ranching and rice cultivation. Fertilizers release nitrous oxide.
Effects of Climate Change
Droughts in regions of Sudan;
Severe crop losses in areas of Africa;
Coastal flooding displacing people in areas of Africa;
Coral bleaching of Great Barrier Reef;
Stronger tropical storms will hit areas of South East Asia (Bangladesh, Philippines, India, Burma);
Temperate forests more susceptible to forest fires;
Tropical diseases will spread to formerly safe areas
Greenhouse Effect
- Short wave radiation passes through earth’s atmosphere
- Some short wave radiation gets absorbed by land and ocean, other gets reflected as long wave radiation
- Some escapes and goes back into space, other stays trapped
- Greenhouse gases (carbon dioxide, methane, nitrous oxide) absorb the energy and re-emit it back into space but also back to the earth’s surface, to warm the atmosphere even more
Mitigation Strategies
- Alternative energy production — renewable energy, cleaner, CO2 not released, becoming cheaper and more competitive, more expensive, solar energy only used during day
- Replanting trees — reduces deforestation, increases forest and land restoration, big investment for governments, deforestation helps rural-poor, absorption of CO2, more interception and shade, less soil erosion, less surface run off, no desertification
- Carbon capture — during production, carbon dioxide sprayed with chemicals so it is extracted and sent through pipelines into the porous rock in the ground, expensive, uses lots of energy
- International agreements — forces countries to set targets, reduces global emissions, expensive, not legally binding, countries can drop out
Adaptation Strategies
- Change in agricultural systems — ensures crop yield is enough, Peruvian potato farmers farming at higher altitudes to get lower temperatures
- Managing water supplies — less water used, houses to be retrofit, desalination plants, locals don’t need to pay, requires lots of energy, expensive for governments
- Reducing risk from rising sea levels — reduces flooding, barriers installed to stop surges, expensive
