Author: masseys

Hazards

Earth Structure
Plate Movements
Volcano Structure
Volcano Case Study
Causes of Earthquakes
Earthquake Case Study
Causes of Hurricanes
Case Study of Hurricane
Short term and Long term Aid

Earth Structure
The planet is made of 4 layers. The Inner Core, Outer Core, Mantel and Crust.
When we talk about Natural Hazards we mainly look at changes taking place in the upper two layers, the Mantle and the Crust.
Crust
The Crust is not one single piece. It is made up of pieces called plates. These plates can have land on them, Continental Plates. They can also have Seas and Oceans on them, Oceanic Plates.
The Continental plates and old and light and cannot be destroyed.
The Oceanic plates are young and heavy which means they can be pushed into the mantle and destroyed.

Mantle
The Mantle is made of liquid rock called Magma. It is not still and moves around. It is this movement that allows the plates to move around causes Earthquakes and Volcanoes.
It moves by convection currents. It is heated by the core which causes the magma to rise. As it nears the surface it cools and starts to drop again. This continues moving the plates sitting on top.
Distribution of Volcanoes and Earthquakes

Using the diagram below describe the distribution of Volcanoes and Earthquakes around the world.
Remember to:
Use examples of countries and continents where they are common.
Use compass directions to help describe where we find them on the planet

Plate Boundary Types
There are three main types of plate boundaries that are responsible for earthquakes and volcanoes around the world.
Destructive – When an Oceanic Plate is forced below a Continental plate and is destroyed, creating a volcano and earthquakes.
Constructive – When two plates move away from each other allowing magma to rise up between them creating volcanoes.
Sliding—When two or more plates move past each other. There sides are not smooth and get caught creating earthquakes.

Structure of a Volcano

Using the diagram above try to answer the following question:
Explain the formation of a Volcano and discuss some of the threats they present. Marks 6

Earthquakes
Earthquakes occur on most plate boundaries. They originate deep in the crust and send shockwaves of energy up through the ground.
They travel as 3 separate waves known as:
P Waves— (push or primary waves) make the land move up and down and travel the fastest.
S Waves— (shake or secondary waves) make the land move from side to side, aren't as fast as P waves.
L Waves— (long waves) spread along the surface of the land , they are the slowest waves but most destructive.
The point where the Earthquake originates is called focus.
The place above the focus where the earthquake reaches land is called the epicentre.
The waves then travel out from the focus.

Causes of Earthquakes
When two plates move near each other they can get caught or snagged on the rough surfaces.
When they get caught pressure begins to build between the two plates.
Eventually the plate move sharply cause the pressure to be released and an earthquake to occur.
Measuring Earthquakes
It is hard to predict an Earthquake but we can measure their strength and make some assumptions about where they could hit.
We measure earthquakes using a Seismograph. We then record the results against the Richter Scale from 1 –10.
We know where Earthquakes have occurred along plate boundaries and where they have not. Using this information we can make assumptions about the areas with little activity, assuming they might have an earthquake next. This is called the Seismic Gap.

2011 Tōhoku Earthquake & Tsunami
Causes:
It was caused by the Oceanic Pacific plate which was pushed underneath the Okhotsk plate along the Japan Trench. When the tension was suddenly released, this caused an earthquake.
The earthquake raised the oceanic plate by 30 foot, causing a large tsunami. The vertical displacement of seawater was the cause of the tsunami that expanded away from the earthquake site.
Impact on the Landscape:
Radiation from nuclear plant caused water contamination and possible contamination of local farm land.
Devastating floods, trapped people in their homes and washed away buildings.
Buildings were damaged by force of tidal wave and earthquake.

11th March 2011 at 2.46pm
Duration: 6 minutes
9.0 Magnitude

Impact on People
16,000 people were killed by earthquake and tsunami.
34,000 people evacuated from their homes.
Over 380,000 homes were destroyed.
Sewage and fresh water pipes were destroyed which meant that diseases could easily spread
Danger of radiation poisoning for those living within 20 miles of the Fukashima Nuclear plant, homes were evacuated.
Short Term and Long Term Aid
USA donated $30 million to help rebuild ( long term aid)
Maldives donated 90,000 cans of tune ( short term aid)
Red Cross received $1billion in aid, used for emergency shelters, emergency medical care and food. (short term aid) Money was also used to help rebuild communities and homes.

Hurricanes
Hurricanes are tropical storms that originate over the Atlantic Ocean. They can also be called Typhoons and Cyclones depending on the Oceans they originate from.
They are formed over water and have wind speeds of over 120km/h.
Conditions and causes
Warm seas, which have a surface temperature of 27⁰C or more.
Warm water depth of at least 60m.
A low pressure weather system with air starting to rise (depression)
Damp moist air of 60% humidity or more.
The combination of the above conditions causes large amounts of air to rise causing large clouds to form. The large amount of evaporation causes these clouds to be heavy with water and suck air in towards the centre. This causes the air to spiral as it rises and creates the circular formation of clouds we are familiar with. As the depression sucks air in faster it increases the wind speed.

Case Study — Hurricane Katrina
Wind speeds of 175mph
Killed 1833 people
$108 billion in damage
Impact on People:
Criminal gangs looted homes
Major roads and highways closed
Major flooding caused loss of power to 3 million people for a week
Cotton and sugar crops destroyed

Impact on Landscape:
Oil pipelines broken, caused spills
Major bridges were destroyed

Aid for Hurricane Katrina:
Short Term Aid:
Emergency aid workers, to rescue people trapped in their homes or New Orleans Superdome.
Emergency shelters.
Clean Water and medicine.
National Guard to protect local people from looters.
Sand bags to protect homes from further flooding.
Long Term Aid:
USA government allocating money to help rebuild.
Investment from American businesses to build up local economies.