Geography-Natural Hazards Flashcards
What are tectonic hazards?
A type of natural hazard
What is a natural hazard?
A naturally occurring event that has the potential to affect people’s lives or property e.g. earthquakes, volcanic eruptions and tsunamis
What are natural hazards called once they have affected peoples lives or property?
Natural disasters
What are earthquakes and volcanoes examples of?
Tectonic hazards, caused by the movement of tectonic plates
What is at the centre of the Earth?
The core, it has an inner bit and an outer bit. The inner core is a ball of solid iron and nickel. The outer core is liquid
What is around the core?
The mantle, which is semi-molten rock that moves very slowly
What is the outer layer of the Earth?
The crust, its very thin, about 20km
What is the crust divided into?
Tectonic plates. They float on the mantle. Plates are made of two types of crust
What are the two types of crust?
Continental crust which is thicker and less dense. Oceanic crust which is thinner and more dense
Why are the plates moving?
Because the rock in the mantle underneath them is moving
What are the places called where the plates meet?
Boundaries or plate margins
What are the three types of plate margin?
Destructive margins, constructive margins and conservative margins
What are destructive margins?
Where two plates are moving towards each other, where an oceanic plate meets a continental plate, the denser oceanic plate is forced down into the mantle and destroyed. This often creates volcanoes and ocean trenches. Or where two continental plates meet, the plates smash together but no crust is destroyed
What is a collision zone?
The area where continental plates collide
What is a subduction zone?
The area where an oceanic plate is being pushed under a continental plate
What are examples of destructive margins?
The pacific plate is being forced under the Eurasian plate along the east coast of Japan
What are constructive margins?
Where two plates are moving away from each other. Magma (molten rock) rises from the mantle to fill the gap and cools, creating new crust
What are examples of constructive margins?
The Eurasian plate and the North American Plate are moving apart at the mid-Atlantic ridge
What are conservative margins?
Where two plates are moving sideways past each other, or are moving in the same direction but at different speeds. Crust isn’t created or destroyed. Either plates moving sideways past each other or plates moving in the same direction at different speeds
What are examples of conservative margins?
The pacific plate is moving past the north american plate on the west coast of the USA e.g. at the San Andreas fault
How can earthquakes occur on destructive margins?
Pressure builds up when one plate gets stuck as its moving down past the other into the mantle
How can earthquakes occur on constructive margins?
Pressure builds along cracks within the plates as they move away from each other
How can earthquakes occur on conservative margins?
Pressure builds up when plates that are grinding past each other get stuck
What happens when the pressure that is built up gets too high?
The plates eventually break past each other, sending out shock waves (vibrations). These vibrations are the earthquakes. The shock waves spread out from the focus-the point in the Earth where the earthquakes starts
What is the epicentre?
The point on the Earths surface straight above the focus. Near the epicentre the shock waves are stronger and cause more damage?
How is the amount of energy released by an earthquake (magnitude) measured?
Using the Richter scale. The scale doesn’t have an upper limit and its logarithmic-meaning an earthquake with a magnitude of 5 is ten times more powerful than one with a magnitude of 4
What plate margins are volcanoes found at?
Destructive and constructive margins
How do volcanoes form on destructive margins?
The oceanic plate goes under the continental plate because its more dense. The oceanic plate moves down into the mantle where its melted and destroyed. A pool of magma forms. The magma rises through cracks in the crust called vents. The magma erupts onto the surface where its called lava, forming a volcano
How do volcanoes form on constructive margins?
The magma rises up into the gap created by the plates moving apart, firing a volcano
Where else do some volcanoes form?
Over parts of the mantle that are really hot (hotspots) e.g. in Hawaii
What two kinds of impacts do earthquakes have?
Primary (immediate effects of ground shaking) and secondary (effect that happen later on)
What are some primary impacts of earthquakes?
Buildings/bridges collapse, people injured/killed by the collapses, transport links destroyed, electricity cables damaged-cutting off supplies, gas pipes broken causing leaks and cutting off supplies, telephone poles/cables destroyed and underground water/sewage pipes are broken causing leaks and cutting off supplies
What are some secondary impacts of earthquakes?
They can trigger landslides and tsunamis which cause more damage, leaking gas can be ignited and start a fire, people left homeless, psychological problems if they knew people that died or lost their home etc, shortage of clean water/lack of proper sanitation-easier for disease to spread, roads blocked/destroyed so emergency vehicles cant get through and businesses are damaged/destroyed causing unemployment
What part of the world do earthquakes have greater impacts?
LEDCs
Why do earthquakes have bigger impacts in LEDCs?
More poor quality housing which are less stable and destroyed easily, infrastructure often poorer, poor roads make it harder for emergency vehicles to reach injured people causing more deaths, don’t have much money to protect against earthquakes or enough money and resources to react straight away so more people are affected by secondary impacts and healthcare is often worse in LEDCs, many hospitals don’t have enough supplies to deal with the large number of casualties so people die from treatable injuries
Why don’t people move away from earthquake prone areas e.g. California?
They’ve always lived there so they would have to leave friends and family. They’re employed in that area so they’d have to find new jobs. They’re confident of the support from their government after an earthquake e.g. to help rebuild houses. Some people think that sever earthquakes won’t happen again in the area so its safe to live there
What are the different ways of reducing the impacts of earthquakes?
Predictions, building techniques, planning, education and aid
How can prediction reduce the impact of earthquakes?
Its impossible to predict when earthquakes will happen, if you could, to would give people time to evacuate, reducing injuries and deaths. There can be clues e.g. lots of small tremors, cracks in rocks and strange animal behaviours e.g. rats abandoning nests. Its possible to protect where they may happen using data from past earthquakes e.g. mapping err they’ve happened showing what places are more likely to be affected again, so these places can prepare for the impacts of an earthquake
How can building techniques reduce the impact of earthquakes?
Buildings can be designed to withstand earthquakes e.g. by using materials like reinforced concrete or building special foundations that absorb an earthquakes energy. Constructing earthquake-proof buildings reduces the number of buildings destroyed by an earthquake, so fewer people will be killed, injured, made homeless and unemployed
How can planning reduce the impact of earthquakes?
Future developments (shopping centres) can be planned to avoid most at risk areas reducing buildings destroyed, Firebreaks made to reduce spread of fires. Emergency services can train/prepare for disasters, practising rescuing people from collapsed buildings reducing amount of people killed. Governments can plan evacuation routes reaching injured and deaths
How can education reduce the impact of earthquakes?
Governments and other organisations can educate about what to do if theres an earthquake e.g. stand in a doorway, and how to evacuate, reducing deaths. People can be told how to make a survival kit containing things like food, water, a torch, radio and batteries, reducing the chance of people dying if their stuck in the area
How can aid reduce the impact of earthquakes?
LEDCS that have been affected can receive aid from governments or organisations, it can be things like food, water, money or people like doctors or rescuers. Aid helps reduce impacts e.g. money aid used to rebuild homes, reducing homelessness