3. Hazardous Environments Flashcards
What is a natural hazard?
An extreme event caused by environmental processes that can cause loss of life, damage to property and disrupt human activity.
Types of natural hazards
- Geological/Tectonic
- Climatic
- Biological
What is a tropical cyclone?
A weather system of very low pressure formed over tropical seas with strong winds and heavy rainfall.
Known as:
Hurricane (USA)
Cyclone (Australia, Indian Ocean)
Typhoon (East Asia)
What is a disaster?
A hazardous geophysical event that affects a vulnerable population.
Distribution of tropical storms
Worst in Eastern Asia (China, HK, Vietnam, Philippines)
North America (Florida, Mexico, Caribbean Islands
Some in Indian Ocean, Java Sea (Australia, NZ, Madagascar)
None on equator due to correolis effect (SG, Malaysia)
Anomaly South America (Brazil)
Measuring tropical storms
Imager, Sounder, Radar
Saffir-Simpson Scale (1-5)
Basaltic lava
Very fluid Extremely hot (1200°C) Fast travelling (retains gas) Found at CONstructive plate boundaries
Properties of andesitic lava
Very viscous (sticky) Very hot (800°C) Slow travelling (loses gases quickly and solidifies) Found at DEstructive plate boundaries
Parts of a volcano
Ash cloud Side vent Crust Crater Lava flow Main vent Magma chamber
Types of solid lava
Pahoe (ropes)
Ah’ah (jagged/sharp)
Pyroclastic flow
Hot moving current of ash and gas
Moves at up to 450mph
Temperature 1000°C
Only happens in andesitic if there is a plug
What gases are emitted from volcanoes?
Sulphur, CO2 and cyanide
Hazardous to life
Sometimes no scent and clear/colourless
What are ash clouds?
Thrown into air during violent eruption
Roofs often collapse under weight
Can asphyxiate humans and animals
What is a lahar?
Mudflow caused by mixture of water and debris
Hot, collects more debris as flows down river valleys
Damage to property
Calderas
Large circular volcanic depressions
Magma withdrawn from shallow underground reservoir
Measuring volcano explosivity
Volcanic explosivity index (1-7)
How do we monitor volcanic activity?
Seismograph (plate turbulence) Thermometers Spectrometer (gas emissions) Geological history Tilt meters
Causes of tropical cyclones
Warm air and sea (27°C) Within tropics Moist humid air Calm winds Low wind sheer
Measuring earthquakes
Richter scale (0-9) Mercalli scale (I-XII)
Layers of the earth
Crust
Mantle
Outer core
Inner core
Constructive/divergent plate boundary
Ridge push forces plates apart
Magma rises to fill gap where crack is
Forms submarine volcanos
eg East African Rise (Kenya/Ethiopia)
Destructive/convergent plate boundary
Plates of oceanic crust move towards continental crust
Friction creates earthquakes
eg Nazca plate moving towards S American plate
Collision plate boundary
Two continental plates meet head on
Neither sink, land buckled up
Fold mountains formed
Earthquakes
Conservative plate boundary
Plates slide past each other at different directions or speed
Pressure built up, lots of friction
Destructive earthquakes
eg San Andreas plate in California
Volcanic hotspots
Plate moves over unusually hot part of mantle
As plates move, volcanoes form
eg Hawai’i
What are some factors affecting risk from hazards?
Hazard (Duration, magnitude, frequency, severity)
Vulnerable (Population, LIC, pool, old, population density)
Preparedness (Supplies, warnings, prediction, aid)
Why do people continue to live in hazardous areas?
Fertile land (productive agriculture, eg Japan, Italy) Lack of education (misinformed, disregard, eg Indonesia) Not enough money (can’t afford to move, eg India) Need jobs (well-paid jobs, eg Japan) Religious beliefs (goddess, eg Hawai’i)
What are some types of attitude towards hazards?
Ill-informed (does not know) Denial (refuses to acknowledge hazard) Accepting (knows hazard) Adaptive (changes to accommodate hazard) Fatalistic (doesn’t mind dying)
