Hazards advanced information Flashcards
What is a destructive plate margin and what hazards can occur there
Where two plates move towards each other.
If it is an oceanic and continental plate the denser oceanic plate subducts below the continental plate. Can create a composite volcano or earthquakes.
Two continental plates will create fold mountains and possibly earthquakes due to pressure build-up.
Two oceanic plates can create deep sea trenches and also volcanic eruptions and earthquakes.
What is a constructive plate margin and what hazards can occur there
When two plates move away from each other and the movement creates pressure on the mantle which can cause magma to escape and create a volcano.
If it occurs between oceanic plates the magma can create ocean ridges when it cools down.
If it happens between continental plates it can create a rift valley where the crust between the plates drops down. These valleys are likely to have volcanos in them.
What is a conservative plate margin and what hazards can occur there
Where two plates are moving past each other. As plates jerk past each other this causes a build-up of pressure which can lead to earthquakes. Can create fault lines.
What is seismicity
The worldwide or local distribution of earthquakes in space time, and magnitude. It refers to the measure of the frequency of earthquakes in a region.
What is vulcanicity
The rising of Molten Rock or Magma or other gaseous materials beneath the earth’s crust forcing its way into planes of weakness or Vent of the earth’s crust to escape quietly or explosively to the surface.
What are is a pyroclastic flow/nuées ardentes
A mixture of superheated gas, ash and volcanic rock that flows down the sides of a volcano. Travels at high speed and a long distance. Since they travel fast they can cause death and destruction with little warning.
What are lava flows
Lava can flow from a vent down the side of a volcano. Speed and distance travelled depends on temperature and viscosity of lava. Low viscosity may travel further. Slow moving allows people time to evacuate but lava will destroy buildings.
What are volcanic gases
Gases such as carbon dioxide can be released when a volcano erupts. Can be harmful to humans when inhaled in a large quantity.
What is pyroclastic fallout/tephra
Pyroclastic fallout is material that has been ejected from a volcano that falls back down to earth. Fallout can range in size. Pyroclastic fallout can crush people.
What is ash fallout
When fallout consists of ash it is called ash fallout. Ash fallout can be harmful if breathed in. It can travel very far.
What are mudflows/lahars
Occur when volcanic material mixes with water(from rainfall or melted glacial ice). Flow very quickly and travel very far.
What is acid rain
Volcanic gases react with water vapour in the atmosphere. Weak sulfuric acid is created. Can damage ecosystems and cause damage to metal.
How is magnitude of volcanos measured
Using the volcano explosivity index. Can be ranked from 0-8 based on how high and far the material is ejected from the volcano.
What is the frequency of volcano eruptions
Some volcanos can erupt around every 100,000 years while some every few months. The ones that erupt less frequently are generally larger and more damaging.
How regular are volcanic eruptions
Some volcanoes erupt at very regular intervals whereas others may be dormant for very long periods of time but then erupt multiple times in quick succession.
How are volcanoes predicted
Changes in ground shape around volcano measured using a tiltometer.
Earthquake sensors to measure seismic activity inside the volcano.
Regularity of eruptions can be used.
Where do volcanoes occur
At constructive plate margins where basaltic lava erupts. Eruptions are frequent and not very violent.
At destructive plate margins where andesitic and rhyolitic lava erupts areas of subductions. Erupt violently and not very often.
What is a primary impact
Something that happens as a direct result of a hazard.
What is a secondary impact
Something that occurs as a result of primary hazards.
How are volcanoes prevented
It is not possible to prevent an eruption but authorities can prevent it from doing significant damage by not developing land around volcanoes.
How are volcanoes prepared for
Make plans for evacuation.
Individuals can be prepared for example having first aid kits.
Search and rescue and firemen teams on standby.
How do people adapt to volcanoes
Strengthen buildings to ensure they do not collapse if a layer of ash falls on them.
Use fertile ground for agriculture.
Why do earthquakes happen
Build up of pressure at plate margins. When the plates jerk past each other these vibrations are called the earthquake. Vibrations spread out from the focus which is where the pressure build up occurred.
How are earthquakes measured
The Richter scale measures earthquakes based on how powerful the vibrations are. It is logarithmic so magnitude goes up by ten as the number increases by one on the scale.
What secondary hazards does an earthquake cause
Tsunamis
Landslides
Soil liquefaction
What is the magnitude and frequency of earthquakes
Hundreds of low magnitude earthquakes occur daily. High magnitude earthquakes occur more rarely.
How random are earthquakes
Earthquakes seem to be random.
How are earthquakes predicted
Scientists can monitor the movement of plates to see which areas could be at risk of earthquakes. It is impossible to predict when they will occur and the magnitude.
What is a tsunami
Underwater earthquakes displace large volumes of water. Can travel very quickly. The bigger the earthquake the bigger the wave.
What is a landslide
Shaking of the ground can dislodge sediment easily that moves downslope easily.
What is soil liquefaction
Can occur when soil is saturated with water and vibrations can cause it to act like a liquid which can cause soil to subside.
How frequent are earthquakes
Hundreds of low magnitude earthquakes occur daily however high magnitude earthquakes happen very rarely.
How regular are earthquakes
Earthquakes don’t seem to follow any particular pattern or trend.
Are earthquakes predicted
It is impossible to tell when an earthquake will hit a certain place however scientists can monitor place tectonic movements to see which areas are at risk.
How are seismic hazards prevented
It is impossible to prevent seismic hazards however authorities can prevent people building on areas prone to soil liquefaction or build sea walls to prevent tsunamis.
How are seismic hazards prepared for
Authorities can have earthquake warning systems that will monitor for smaller seismic waves which could tell if a larger earthquake is coming. Tsunami warning systems can also bet set up.
Firemen and search and rescue teams can be created for a seismic hazard occurring.
How can people adapt to seismic hazards
People can live in earthquake buildings for example by having special foundations that can absorb an earthquakes energy.
In places susceptible to tsunamis people may build their houses with very tall foundations.
How do tropical storms form
Over warm waters when warm air rises and condenses it releases energy which gives energy to wind. To form there needs to be an area of low pressure so that air converges and rises, sea water that is at least 27 degrees celsius and to be at least 5 degrees from the equator so the coriolis effect can work.
Where do tropical storms form
Around the tropics because that is where water is warm enough.
What are tropical storms called in different parts of the world
Caribbean sea - hurricanes.
Bay of Bengal - cyclones.
China sea - typhoons.
When do tropical storms lose their energy
When they go over land because their supply of warm moist air is cut off.
How do tropical storms move
They move westwards due to the trade winds of the tropics. The coriolis effect causes them to move away from the equator.
How do tropical storms spin
Clockwise in the northern hemisphere anti clockwise in the southern hemisphere.
How is tropical storm magnitude measured
Using the Saffir-Simpson scale. Storm Katrina was a category 3 when it hit land so its wind speed was around 200 km/hr. The Saffir-Simpson scale also estimates how much damage a tropical storm will do with category one being limited damage and category five being catastrophic.
What do high winds do in a tropical storm
Wind speeds can be up to 300km/hr. This means they can destroy buildings and carry things like cars and trees long distances before smashing them into things.
What is a storm surge
A large increase in sea levels caused by winds pushing water towards the coast.
How do tropical storms cause flooding
Heavy rainfall suddenly can cause river discharge to increase suddenly which could then lead to it bursting its banks.
How do tropical storms cause landslides
Water from heavy rainfall infiltrates the soil and rock making it more susceptible to landslides.
What are short term responses to Tropical storms
Evacuating people from the areas at risk of the storm.
How frequent are tropical storms
There are around 80 tropical storms on average around the world each year.
How are tropical storms predicted
Satellites and aircraft determine the current location and intensity of the storm. This information is used along with computer forecast models to predict the future path and intensity of the storm.
How can tropical storms be prevented
Tropical storms cannot be prevented but scientists can use them to see which areas are at high risk of tropical storms and avoid developing them.
How can tropical storms be prepared for
Governments can plan evacuation routes and teach people how to prepare for a tropical storm.
How can people adapt to tropical storms
Reinforced buildings with secure roofs so they are not destroyed by wind and houses on stilts could possibly avoid the risk of flooding.
How can vegetation type make wildfires more likely
Closely spaced trees allow fires to spread easily. Some trees like pines contain natural oils which allows them to burn easier.
How can fuel type make wildfires more likely
Dry material will burn easier for fires. Large amounts of dry material also allow the fire to burn for longer periods of time and spread.
How can climate and recent weather make wildfires more likely
Rain must be sufficient so that vegetation can grow to be fuel for wildfires. Area should have a distinct dry season so there is dry, flammable vegetation. Strong wind provides more oxygen to fuel the fire and help spread it.
How can fire behaviour make wildfires more likely
Fire can burn differently. A creeping fire will travel slowly whereas a running fire will travel quickly. Fires can throw out burning debris which helps it spread.
What are natural causes of a wildfire
A lightning strike can cause a fire if it occurs without much rain. Volcanic eruptions can also cause wildfires.
What are human causes of a wildfire
Cigarette buts dropped carelessly and out of control barbecues or campfires can start fires. Deliberate fires can also be a cause which is called arson.
How are wildfires prevented
Educate the public about the risks of using campfires. Provide firebeaters to put out fires before they spread.
How do people prepare for wildfires
Emergency evacuation plan and emergency supplies for each household. Emergency shelters available for people.
How do people adapt to living in areas susceptible to wildfires
Buildings are made out of fire resistant materials. Fire breaks (gaps between trees) are made around settlements to stop fires spreading to buildings.
What is risk sharing
A form of community preparedness, whereby the community shares the risk posed by a natural hazard and invests collectively to mitigate the impacts of future hazards.
What is fatalism
Where people accept that there will be a risk but choose to do little about it prior to the event. The response after the event will be reactive but the hazard event will often lead to large loss of life.
What is adjustment/adaption
For places which experience regular hazards a response is often to adapt or adjust their behaviour to be able to cope with future events better.
