1.1 Challenge of Natural Hazards Overview (Paper 1) Flashcards
<p>What is a <strong>natural hazard</strong>?</p>
<p>A<strong>natural event</strong>(for example earthquake, volcanic eruption, tropical storm, flood) that threatens people or <strong>has thepotential to cause damage, destruction and death</strong></p>
<p>What is a hazard risk?</p>
<p>Hazard risk is the chance or probability of being affected by a natural event</p>
<p>List some examples of natural hazards (and their category if you can)</p>
<p><u><strong>Tectonic hazards</strong></u>(e.g. earthquake, tsunami, volcanic eruption)</p>
<p><u><strong>Atmospheric hazards</strong></u>(e.g. hurricanes)</p>
<p><u><strong>Geomorphological hazards</strong></u>(e.g flooding)</p>
<p><u><strong>Biological hazards</strong></u>(e.g. forest fires)</p>
<p>What factors affect a hazard risk?</p>
<p>1.<strong>Poverty</strong>- poorer places will struggle to adequately prepare for a hazard or be able to respond</p>
<p>2.<strong>Magnitude</strong>- the severity of the hard will make the impacts worse</p>
<p>3.<strong>Population density</strong>- areas that have high populations will experience more destruction</p>
<p>4.<strong>Education</strong>- how educated the population are to react and prepare forthe hazard</p>
<p>Describe the structure of the earth starting from the outermost layer</p>
<p>OUTERMOST: 1.<strong>Crust</strong>- the outermost layer of the Earth, broken into tectonic plates.</p>
<p>2.<strong>Mantle</strong>- semi-molten part of the Earth.</p>
<p>3.<strong>Outer core</strong>- liquid iron and nickel</p>
<p>CENTRE: 4.<strong>Inner core</strong>- solid iron and nickel</p>
<p>What causes the plates to move?</p>
<p>Convection currents in the mantle</p>
<p>What are convection currents?</p>
<p>Circulating movements of magma in the mantle caused by the heat of the core</p>
<p>Describe the globaldistributionof <strong>earthquakes.</strong></p>
<p>Earthquakes<strong>occur in lines</strong>which coincide with<strong>plate margins</strong>.There are many along the western coast of North and South America</p>
<p>Describe the global<strong>distribution</strong>of volcanic eruptions</p>
<p>Volcanoes are found both<strong>on land and in the sea</strong>.They tend to befound along <strong>plate margins</strong>. Some volcanoes are found in the<strong>centre of plates</strong>. These are known as<strong>hot spots</strong>. There is a large band of volcanoes around the Pacific Ocean known as the Ring of Fire</p>
<p>What is<strong>oceanic</strong>crust?</p>
<p>The part of the Earth's crust which is below the oceans</p>
<p>What is<strong>continental</strong>crust?</p>
<p>The part of the Earth's crust that makes the continents</p>
<p>What is the<strong>difference</strong>between oceanic and continental crust?</p>
<ul><li>Oceanic crust is thinner (5-10km thick)and denser than continental crust</li><li>Oceanic crust is recycled at destructive margins as it subducts under the continental crust</li><li>Continental crust is thicker (20-200km thick) and is less dense than oceanic crust</li><li>Continental crust cannot be destroyed</li></ul>
<p>What isa<strong>conservative</strong>plate margin?</p>
<p>A plate margin where the tectonic plates are<strong>slidingpast</strong>each other</p>
<p>What is a<strong>constructive</strong>plate margin?</p>
<p>A plate margin where the tectonic plates are<strong>movingapart</strong></p>
<p>What is a<strong>destructive</strong>plate margin?</p>
<p>A plate margin where an<strong>oceanic</strong>and a<strong>continental</strong>plate<strong>collide</strong></p>
<p>What are<strong>tectonichazards</strong>?</p>
<p>Threats posed by earthquakes, volcanoes etc</p>
<p>Define <strong>epicentre</strong></p>
<p>The point on the ground directly above the focus (centre) of the earthquake</p>
<p>Define <strong>focus</strong></p>
<p>The point of origin of an earthquake</p>
<p>Define <strong>magnitude</strong>?</p>
<p>The size of an earthquake</p>
<p>Define '<strong>magnitude</strong>'?</p>
<p>The size of an earthquake</p>
<p>What is an ocean trench?</p>
<p>A deep depression on the ocean floor formed at the subduction zones of destructive plate margins</p>
<p>What are tectonic plates?</p>
<p>The large pieces of broken crust that cover the earth</p>
<p>What is a plate<strong>margin</strong>?</p>
<p>The boundary between two tectonic plates</p>
<p>What are<strong>primaryeffects</strong>?</p>
<p>The impacts of a natural disaster that happen immediately or soon after the event</p>
What are secondary effects?
The after-effects of a disaster eg. disease spread or economic losses
Define tsunami
Huge waves caused by earthquakes under the sea
List two characteristics of an oceanic crust
5-10 km thick
Dense
Destroyed at destructive plate margins
Forms constantly at constructive plate margins
Geologically young compared to continental crust
List two characteristics of a continental crust
25-100km thick
Less dense (than oceanic)
Cannot be destroyed. New crust is not formed
It is geologically old 3-4 billion years old
What is an earthquake?
Earthquakes are vibrations in the Earth's crust that creates shaking at the surface. They are highly unpredictable and often occur suddenly without warning, mainly on the plate margins
Do earthquakes happen on all four plate boundaries?
Yes
Why do Earthquakes occur?
Earthquakes occur because stresses build up between the plates as one plate passes another
As the plates move past one another they don't do so smoothly, rather, they snag and grind, allowing energy to build-up
When the plates eventually move again this energy is released as shock or seismic waves through the Earth's crust
List two characteristics of a composite volcanoes
Made up of alternating layers of lava and ash (other volcanoes just consist of lava)
Found at destructive boundaries
Often has pyroclastic flows. A pyroclastic flow is a mixture of hot steam, ash, rock and dust
A pyroclastic flow can roll down the sides of a volcano at very high speeds and with temperatures of over 400°C
List two characteristics of a shield volcano
Shield volcanoes are usually found at constructive or tensional boundaries
They are low, with gently sloping sides
They are formed by eruptions of thin, runny lava
Eruptions tend to be frequent but relatively gentle
Can we predict volcanic eruptions and earthquakes?
Volcanoes - Yes
Earthquakes - No
List some reasons why people live in areas at risk from tectonic hazards
Fertile farmland on volcanic soil (environmental)
Income from tourism (economic)
Lack of other alternatives (social)
Mining precious minerals (socio-economic)
How do we measure the size of the earthquake?
Richter Scale - Measured from 1-9
At which plate margin can earthquakes occur?
All plate margins (constructive, destructive and conservative)
At which plate margin can volcanoes occur?
Shield volcanoes form at constructive margins
Composite volcanoes form at destructive margins
What type of plate margin does Nepal lie on?
Collision
What type of plate margin does L'Aquila lie on?
Constructive
What was the magnitude of the L'Aquila earthquake?
6.3 on the Richter scale
What was the magnitude of the Nepal earthquake?
7.9 on the Richter scale
Describe the primary effects of the Nepal earthquake
- 9,000 deaths
- 20,000 people injured
- 3 million without a home
- US $5 billion of damage
- 50% of shops destroyed
- Airport became congested as aid arrived
- Schools and buildings destroyed
- 1.4 million people needed food and water days after the earthquake
Describe the secondary effects of the Nepal earthquake
- Ground shaking triggered landslides and avalanches, blocking roads, making relief difficult
- Avalanches killed 19 people
- A landslide blocked the Kali Gandaki River - causing a risk of flood
Describe the primary effects of the L'Aquila earthquake
- 300 people were killed
- 1,500 were injured
- Hospitals damaged
- 67,000 homeless
- 10,000 buildings collapsed (including medieval buildings and monuments, universities and hospitals)
Describe the secondary effects of the L'Aquila earthquake
- Aftershocks triggered landslides
- L'Aquila University student numbers reduced
- House prices increased
- Some areas were so unsafe they were declared as 'red zones' which has led to a decrease in business and tourism
Describe the immediate responses to the L'Aquila earthquake
- Hotels (and some train carriages) provided shelter for 10,000 people
- Italian Red Cross searched for survivors
- The British Red Cross raised £170,000 in aid
- A state of emergency was declared which sped up international aid efforts
- The EU donated US$550 million to help with rebuilding costs
Describe the immediate responses to the Nepal earthquake
- Other countries helped in search and rescue and provided medical supplies
- Helicopters rescued people caught in the avalanche on Mount Everest
- Half a million tents needed to provide shelter for the homeless
- Field hospitals were set up to alleviate pressure on hospitals
- 300,000 people migrated from Kathmandu
- Social media helped to map damage of area
Describe the long term responses to the Nepal earthquake
- Roads repaired and landslides cleared
- Lakes, formed by landslides damming rivers, were emptied to avoid flooding
- Homeless were re-housed
- Schools to be rebuilt or repaired
- Reopening of some heritage sites to boost tourism
Describe the long term responses to the L'Aquila earthquake
- Residents did not have to pay tax during 2010
- University students were given free public transport, discounts on educational equipment and were exempt from university fees for 3 years
- Years of rebuilding homes
- Approximately 15 years to rebuild historic centres
Describe what is meant by monitoring tectonic hazards
Using scientific equipment to detect warning signs of events such as a volcanic eruption
What is meant by a prediction of a natural event?
Using evidence and monitoring information to make a judgement about when an earthquake or volcano is likely to happen
What is meant by tectonic hazard protection?
Designing buildings to withstand tectonic hazards
What is meant by planning for tectonic hazards?
Identifying places at risk or tectonic hazards and ensuring people know what to do in the event of an earthquake/volcano
Give examples of monitoring tectonic hazards
Volcanoes
- satellites & laser beams detect changes to the volcano shape
- increasing amounts of gases such as carbon dioxide and hydrogen sulfide are given off before an eruption
Earthquakes
- there is no reliable way of monitoring and predicting earthquakes
Give examples of how to plan for tectonic hazards?
Volcanoes & Earthquakes
- Identify areas at risk and don't build on these areas
- Plan to evacuate high-risk areas
Give examples of how to protect against tectonic hazards
Volcanoes
- Divert lava away from built-up areas by using explosives
- Reinforced foundations
- Shock absorbers to absorb ground shaking
- Automatic shutters to cover windows preventing shattering glass
- Rolling weights on roof to counteract shock waves
Earthquakes
