Topic 1 - Natural Hazards Flashcards
Define a natural hazard and its risk to people
A NATURAL process which could cause death, destruction to property and possessions, injury or disruption to humans
major risks
Difference between natural hazard and natural disaster
A natural disaster is a natural hazard that has actually happened
What are the types of natural hazards
GEOLOGICAL - caused by land and tectonic processes. Includes volcanoes, earthquakes, landslides and avalanches
METEOROLOGICAL - caused by weather and climate. Includes tropical storms, heat waves and cold spells (climate change may increase risk)
How does VULNERABILITY affect the risk of natural hazards (probability of people being affected)
- more people, greater probability to be affected
- eg / an area with a high population density on a flood plain (Bangladesh) vulnerable to flooding
How does CAPACITY TO COPE affect the risk of natural hazards (probability of people being affected)
- better the population can cope, lower the risk of severity caused
- eg / HIC’s better ability to cope because they can afford defences and evacuation
How does NATURE OF NATURAL HAZARDS affect the risk of natural hazards (probability of people being affected)
1) TYPE - some are greater risk
2) FREQUENCY - if they occur more often they may be higher risk
3) MAGNITUDE - most severe hazards have greatest effects
Define PRIMARY effects of natural disasters and main examples
The IMMEDIATE impacts caused by the hazards themselves
- destruction of buildings and roads by earthquakes, volcanic eruptions or tropical storms
- people are injured or killed eg when buildings collapse
- crops and water supplies can be compromised
- electricity cables, gas pipes, and communication networks can be damaged, cutting off supplies
Define SECONDARY effects of natural disasters and main examples
Happen LATER on, often as a result of the primary effects
- initial hazard can trigger other hazards (earthquakes —> tsunamis)
- blocked roads and bridges —> emergency vehicles and aid cant get through
- shortage of clean water and sanitation —> easier disease spread
- damaged crops, livestock killed —> food shortages
- damage to business can cause unemployment, restriction is expensive —> country’s economy can be weakened
IMMEDIATE responses to a natural disaster
- evacuation (preferably before)
- treat injured, rescue anyone cut off by damage to roads or bridges
- recover dead bodies to stop disease
- provide temporary electricity or gas supplies if needed
- provide food, water and shelter to the homeless
- foreign governments give aid (supplies, aid workers or financial assistance)
LONG TERM responses to a natural disaster
- repair homes, rehouse people without a home
- repair/rebuild buildings, roads, railways and bridges
- improve forecasting, monitoring and evacuation plans
- improve building regulations (buildings can withstand future hazards)
- boost economic recovery (eg by promoting tourism)
Explain TECTONIC PLATES and their features
- tectonic plates are the crust broken into slabs, they float on the mantle
- plates are made of 2 types of crust;
—> CONTINENTAL crust (thicker and less dense)
—> OCEANIC crust (thinner and more dense) - plates are moving due to convection currents
- the places they meet are called PLATE MARGINS or PLATE BOUNDARIES
Explain a DESTRUCTIVE plate margin
- two plates moving TOWARDS each other
- oceanic meets continental, denser oceanic is subducted and destroyed, creating magma
- volcanoes and ocean trenches occur
- when its two continental meeting fold mountains occur as ground is folded upwards
Explain a CONSTRUCTIVE plate margin
- two plates moving AWAY from each other
- magma rises from the mantle to fill the gap and cools, creating a new crust
- volcanoes and earthquakes occur
Explain a CONSERVATIVE plate margin
- two plates moving sideways past each other or moving in same direction at same speed
- crust isn’t created or destroyed
- earthquakes occur
How are the plate margins distributed in the world
DESTRUCTIVE - west coast of South America, oceanic Nazca plate being subducted beneath continental South American plate, creating the atacama trench
CONSTRUCTIVE - movement of Eurasian plate and the North American plate away from one another, forming the mid Atlantic ridge
CONSERVATIVE - San Andreas fault, the Pacific plate is moving in the same direction as the North American plate but faster
How are volcanoes formed at plate margins
{DESTRUCTIVE}
- Denser oceanic plate moves into mantle where it melts
- Pool of magma forms, then rises through the cracks in crust called vents
- Magma erupts (lava when reaches surface) forming a volcano
{CONSTRUCTIVE}
1. Magma rises into gap caused by plates, forming a volcano
Explain distribution of volcanoes and the effect they can have
- some volcanoes form over parts of the mantle that are really hot (hotspots) eg in Hawaii
- when a volcano erupts it emits lava and gases, as well as ash which can cover land and block the sun and form pyroclastic flows (super-heated currents of gas, ash and rock)
Explain how earthquakes are caused at plate margins
Occur at ALL THREE plate margins
- Caused by tension that builds up:
——> CONSTRUCTIVE tension caused along cracks in the plates as they move away from each other
——> DESTRUCTIVE tension builds when one plate gets stuck as it moves past the other
——> CONSERVATIVE tension builds when plates that are grinding past each other get stuck - Plates jerk past each other, causing vibrations called shockwaves (earthquake)
- Shock waves spread out from focus (where it starts) waves are stronger near the focus and cause more damage
- Epicentre - point on earths surface straight above the focus
- Earthquakes measured using the moment magnitude scale
Give an example of an earthquake in a high income country (Basic facts)
KAIKOURA, NEW ZEALAND
Date: 14th November 2016
GDP per capita: US $40 331
Plate boundary: destructive and conservative - Pacific plate subducting beneath the Australian plate to the north, sliding past it to the south
Magnitude: 7.8 on the moment magnitude scale
Describe the primary effects of the earthquake in the HIC
- 2 people died and over 50 injured
- tens of thousands of homes damaged/destroyed
- 60 needed emergency housing
- cost of damage $8.5 billion
- over 200km of road and over 190km of rail line destroyed
- communications, water, sewerage and power supples were cut off
Describe the secondary effects of the earthquake in the HIC
- triggered up to 100,000 landslides blocking major road and rail lines
- major landslide blocked the Clarence River, leading to flooding and the evacuation of 10 farms
- generated a tsunami, waves of around 5m leaving debris up to 250m inland
Give an example of an earthquake in a low income country (Basic facts)
GORKHA, NEPAL
Date: 25th April, 2015
GDP per capita: US $690
Plate boundary: destructive — Indo-Australian plate subducted beneath the Eurasian plate
Magnitude: 7.8 on the moment magnitude scale
Describe the primary effects of the earthquake in an LIC
- around 9000 deaths and 22000 casualties
- estimated 800,000 buildings damaged or destroyed
- 4 million homeless
- cost of damage, US $5 billion
- roads and bridges destroyed
- water tanks and pipes were destroyed, 2 million without access to clean water and sanitation
Describe the secondary effects of the earthquake in an LIC
- triggered avalanche on Mount Everest — 18 dead
- mountain roads blocked by landslides, preventing emergency aid reaching remote areas
- lack of clean water, outbreak of typhus killing at least 13
