Natural Hazards

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Grace

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Natural hazards are extreme natural events that can cause loss of life, extreme damage to property and disrupt human activities
EXAMPLES OF NATURAL HAZARDS
avalanche
drought
tornadoes
hurricanes
volcanic eruptions
mudflow
snow
lightning
landslide
earthquakes
Natural hazards can be split into 3 categories:
atmospheric
geological
flooding
FACTORS INCREASING THE RISK FROM NATURAL HAZARDS:
poverty
farming
climate change
urbanisation
WHAT HAPPENS AT PLATE MARGINS?
There are three types of plate margin:
destructive - two different plates meet
constructive - two plates move apart
conservative - plates move past each other
DESTRUCTIVE PLATE BOUNDARIES
A destructive plate boundary is found where a continental plate meets and oceanic plate.
The oceanic palate subduction under the continental plate because it is denser. As the plate descends it starts to melt due to the friction caused by the movement between the plates. This melted plate is not hot, liquid rock (magma). The magma rises through the gaps in the continental plate. If it reaches the surface the liquid rocks forms a volcano.
CONSTRUCTIVE PLATE BOUNDARIES
Oceanic plates move apart at constructive plate boundaries. This movement is caused by convection currents in the soft rock beneath the plates.
As the plates move apart, magma rises between the plates. This forms small volcanoes on the ocean floor. However, since the magma can escape easily at the surface, the volcano does not erupt with much force. The magma hardens to form new crust on the ocean floor. This is causing the ocean floor to spread by about 10cm a year
Gentle earthquakes also occur at constructive plate boundaries
CONSERVATIVE PLATE BOUNDARIES
Two plates moving past each other in either direction or the same direction. As it here is no movement of magma, only earthquakes occur here
Seismic energy = shock waves created by an earthquake
Epicentre = the point on the surface directly above an earthquake
Fault = a crack in the earths crust along which plates move
Magnitude = the strength or energy of an earthquake
Focus = the point underground where the rock snaps and the earthquake starts
HOW DO EARTHQUAKES FORM?
Two giant slabs of rock or plates are sliding past each other along a fault
But there surface rocks are stuck, because there is friction between them
Stress builds up in the surface rocks
The stress becomes so strong that the rocks start squashing and stretching like plasticine
The rock cannot deform any more, so it suddenly becomes brittle
It snaps, sending out shock waves of seismic energy in all directions
The Richter scale = measures the size of the seismic waves during the earthquake
Mercalli scale = this measures how much damage is caused by the earthquake based on observations
Primary effects = resulting directly from the earthquake itself
secondary effects = happen as a result of the primary effects
People chose to live close to volcanoes because they feel that the advantages outweigh the disadvantages.
Most volcanoes are perfectly safe for long periods in between eruptions, and those that do erupt more frequently are usually thought of, by the people who live there as being predictable
Hazard perception = they way in which people think a hazard will affect them
ADVANTAGES OF LIVING NEAR VOLCANOES
minerals - valuable minerals such as copper, gold, silver, lead, zinc and even diamonds are all associated with volcanic regions
fertile soil - volcanic soils are some of the most fertile in the world due to the weathering of volcanic products such as ash, which release valuable nutrients which enrich the soil
geothermal energy - heat from magma sources close to the surface in volcanic areas can be used as a source of geothermal energy
tourism - due to spectacular scenery associated with volcanic landscapes and unique features
METHODS OF MONITORING AND PREDICTING EARTHQUAKES
a seismograph measures seismic waves and can help predict if a major earthquake is about to happen
animal behaviour - many observations have shown that animals react to an earthquake before the event and well before human beings
laser beams can be used to detect plate movement by directing the beam across the fault line
HOWEVER, despite the use of these different method, it is still extremely difficult to predict the time, date and exact location of earthquakes
HOW ARE TROPICAL STORMS FORMED?
Warm ocean water provides energy for the hurricane and causes more evaporation making humid air and clouds
winds coming together force air upwards
wind flows outwards above the storm, allowing the air below to rise
humid air rising makes the clouds of the storm
light winds outside the hurricane steer it and let it grow
HOW ARE TROPICAL STORMS MEASURED?
The Saffir-Simpson scale is a 1-5 rating based on a tropical storms sustained wind speed at the time. It can be used to give an indication of the potential damage and flooding
CLIMATE CHANGE AND TROPICAL STORMS - INCREASED DISTRIBUTION
in the past some areas of the world did not have ocean temperatures of 27*C so tropical storms were not formed there
however, due to climate change some areas of the world now have the sea temperatures of 27*C needed to form a tropical storm
the distribution of tropical storms has increased further away from the equator and will increase further in the future
CLIMATE CHANGE AND TROPICAL STORMS - INCREASED FREQUENCY
in the past, there were not as many tropical storms because ocean temperatures didn’t always hit the 27*C needed to cause the formation of a tropical storm
however, due to climate change ocean temperatures the the 27*C needed to form a tropical storm more often. This means that tropical storms are occurring more often
tropical storms are occurring more now than they did in the past and they will occur more in the future
CLIMATE CHANGE AND TROPICAL STORMS - INCREASED DURATION
in the past, tropical storms didn’t last very long because they didn't stay at 27*C for very long and when the temperature of the ocean water drops below 27*C the tropical storm starts to die
however, climate change is causing the temperature of ocean water to be at 27*C for longer so tropical storms are lasting longer
tropical storms are lasting longer then they did and will last longer in the future
CLIMATE CHANGE AND TROPICAL STORMS - INCREASED INTENSITY
in the past, tropical storms weren’t as strong. This was because they didn’t last for very long
the longer tropical storms exist the more powerful they get
climate change has meant that the temperature of ocean water is staying at 27*C for longer
this means tropical storms last for longer and get bigger
tropical storms are stronger than they were in the past and they will get more powerful in the future
HOW WOULD YOU MONITOR A TROPICAL STORM?
hurricane hunters : tracking by air
satellites : weather watchers in space
supercomputers : where it all comes together
FPA
forecast
prepare
act
FORECAST (Preparation for tropical storms)
hurricane hunters - aircrews that fly into tropical storms to gather weather data, accurately predicts hurricane development and movement
satellites - weather satellites watch hurricanes from orbit, snapping visible images of swirling clouds and measuring weather patterns with radar and infrared sensors
supercomputers - the enormous amounts of data need to be sorted and be calculated by massive, high-tech supercomputers
PREPARE (Preparation for tropical storms)
education - leaflets, posters and school lessons are common ways of spreading the message and in the USA there is an annual hurricane preparedness week when schools, businesses and families are all encouraged to plan for possible hurricanes
building design - considering raising electrics, building on stilts, building cyclone shelters, building away from rivers
building adaption - people are encouraged to think about how they will protect their home and belongings
emergency kits - people are encouraged to have a hurricane emergency kit on standby
ACT (Preparation for tropical storms)
building defence - this might include boarding up windows and doors and securing down anything that could be blown away
evacuation - people could evacuate the area. A mandatory evacuation is when the authorities command that everyone in an area must leave
WHAT HAS CAUSED THE CLIMATE TO CHANGE IN THE PAST?
volcanic eruptions
asteroid collisions
sunspots
orbital changes
ERUPTION THEORY
powerful eruptions release ash and gas high into the atmosphere
if the ash and gas rise high enough, they can travel around the earth
this forms a blanket around earth and stops sunlight getting through, instead it reflects off the ash and gas back into the atmosphere
this causes the planet to get cooler
ASTEROID COLLISION THEORY
around every 500,000 years an asteroid measuring 1km strikes earth
as it impacts it throws up millions of tonnes of ash and dust into the atmosphere
this then blocks out the sun, making the earth cooler
SUNSPOT THEORY
sunspots are black areas on the surface of the sun
lots of spots mean the sun is more active and firing out more solar energy
this theory would affect the earths climate for a few hundred years and would change temperatures by 1-2*C
sunspots have been identified as the possible cause for two different climatic periods: little ice age and medieval warm period
ORBITAL THEORY
over long periods of time the earths orbit can change
these changes affect the amount of sunlight the earth gets and where that sunlight falls, therefore affecting our climate
this theory would affect the earths climate for thousands of years and is enough to start or end an ice age
The greenhouse effect is a natural process and without it life on earth would be impossible. Without the greenhouse a
gases in our atmosphere the earth would be a frozen wasteland
Weather = the day to day conditions of the atmosphere e.g. temperature, cloud cover and wind direction