Natural Disaster

TARIQ M.USMANI ASSOCIATE PROFESSOR

What is the difference between Hazard and Disaster? A hazard is a situation where there is a

threat to life, health, environment or property. A disaster is an event that completely

disrupts the normal ways of a community. It brings on human, economical, and environmental losses to the community which the community cannot bear on its own.

Hazards are natural or manmade phenomenon that are a feature of our planet and cannot be prevented. In their dormant state, hazards just pose a threat to life and property. These hazards are termed as disasters when they cause widespread destruction of property and human lives. Once a hazard becomes active and is no longer just a threat, it becomes a disaster. We can prevent hazards becoming disasters if we learn to live in harmony with nature and take precautionary steps.

Disasters

Disasters are hazards that cause destruction or environmental changes. The types are Natural disasters Man made disasters A natural disaster is the effect of a natural

hazard (e.g., flood, tornado, hurricane, volcanic eruption, earthquake, or landslide)

List of top 10 natural disasters 1. Earthquake 2. Volcanic Eruption 3. Cyclone 4. Tornado 5. Tsunami 6. Flood 7. Wildfire 8. Drought 9. Avalanche 10. Landslide

What are Earthquakes? The shaking or trembling caused by the

sudden release of energy Usually associated with faulting or breaking

of rocks Continuing adjustment of position results in

aftershocks When parts of the earth, called plates, move

against each other giant shock waves move upwards towards the surface causing the earthquake.

What is a volcano? A point on the earth’s crust

where magma forces its way to the surface Ash and gases may also escape

A volcano is an opening which throws out magma from form within the Earth to the Earth’s surface. Magma coming out from a volcano is

referred to as lava . A volcano can be active if it is in the

stage of erupting lava. A volcano is called a dormant volcano

in case it has not erupted in a very long time.

When this dormant volcano does not erupt for thousands of years, it is termed as an extinct volcano. Depending upon the explosive nature of the volcano, different land forms can be formed such as a plateau (if the residue spreads, which means the volcano is not explosive in nature) or a mountain ( if it explodes, which means the volcano is explosive in nature)

Three common volcanoes are: Shield volcano They are formed by running lava and

spread to a larger space. The magma coming out is known as basaltic magma. Composite volcano They are also called strato-volcanoes. They are explosive in nature The magma is known as andesitic magma. Caldera volcano It is hugely explosive in nature which

makes the volcano collapse and results in a depression on the surface.

• MUST KNOW TERMS • ACTIVE VOLCANO – An active volcano is one that erupts

regularly. • DORMANT VOLCANO – A dormant volcano is one that

has not erupted for many years, as explained above. • EXTINCT VOLCANO – An extinct volcano is a volcano

which is not active at all. • GEYSERS – Caused by the heat trapped inside the earth

which causes the heating of ground water. They come out from the surface at certain places as springs in the air.

• ASH – Small particles of lava after being thrown up outside the Earth through the vent in the volcano

• THE REASON FOR VOLCANOES • The reason for volcanic activity is the movement of tectonic

plates. • DIFFERENCE BETWEEN MAGMA AND LAVA • Magma is liquid rock inside a volcano. Lava is liquid rock

(magma) that flows out of a volcano. • LAVA COOLS SLOWLY BECAUSE…. • Lava is a poor conductor of heat. Lava flows slow down and

thicken as they harden. • What is the Ring of Fire? • The Pacific Ring of Fire is an area of frequent earthquakes

and volcanic eruptions in the Pacific Ocean. It has over 50% of the world’s active and dormant volcanoes.

Where do they occur?

• On subduction zones • On constructive plate boundaries • On hot spots

Cyclones

• Cyclones turn counter-clockwise in the northern hemisphere and clockwise in the southern hemisphere. This is because it follows the rotational movement of the earth.

• The biggest cyclone recorded is the Bhola cyclone. It hit the coast of today's Bangladesh in 1970 with a death toll of around 500,000.

The start of a cyclone is when air heated by the sun rises very swiftly which creates areas of very low air pressure. As the warm air rises it becomes loaded with moisture which condenses into huge thunder clouds.

Cool air rushes in to fill the void that is left, but because of the consent turning of the earth axis the air is bent inwards then spirals upwards with great force.

The swirling wind rotate faster and faster, forming a huge circle which can be up to 2,000 km across.

At the centre of the storm is a calm, cloudless area called the eye where there no rain and the winds are fairly light.

As the cyclone build up it begins to move. It is sustained by a steady flow of moist air.

The strongest winds and heaviest rains are found towering around clouds which merge into a wall about 20-30 km from the storm’s centre.

Winds around the eye can reach speeds of up to 200km/h and a fully developed cyclone pumps about 2 million tonnes of air per second. This results in more rain being released in a day falls in a year in a city like London.

Tornados (Twisters)

• A tornado is a violently rotating column of air that is touching both the ground and a cumulonimbus cloud.

• Tornado conditions are caused when different temperatures and humidity meet to form thunder clouds

• “Twisters” can attain speeds up to 100 miles an hour

Tornados • The biggest tornado recorded was the

Hallam, Nebraska tornado on May 22, 2004. It was around 2.5 miles big and had a death toll of around 160.

• The deadliest tornado recorded occurred in Daultipur and Salturia, Bangladesh on April 26th, 1989. 1300 recorded dead and 12,000 injured.

Tsunami’s

• Tsunami means harbor wave and is caused by the displacement of a large body of water normally an ocean or a large lake.

Tsunami’s

• The biggest tsunami ever happened at Lituya Bay, Alaska on July 9, 1958. The mega tsunami was around 150 meters tall.

• The tsunami caused by 2004 Indian Ocean earthquake, is the 6th deadliest Natural disaster in recorded history with a death toll of 230,210 – 280,000.

Floods

• Floods are caused when water overflows from a water body.

• One of the biggest floods in the world is probably the Yellow river in China 1887 which killed between around 900,000.

Wildfire

• A wildfire is any uncontrolled fire in the countryside or wilderness.

• Other names for a wildfire are brush fire, bushfire, forest fire, desert fire, grass fire, hill fire, peat fire, vegetation fire, and veldfire.

• One of the largest wildfire is the 1910 wildfire

Droughts

• A drought is a long period of time in which a certain region receives a shortage of water

• Lasting three years from 1958 to 1961, the Great Chinese Famine is the worst on record, 15 to 43 million were killed as a result

• USA has been hit by a huge drought in 2012 decreasing corn income by 12%

Avalanches

• An avalanche is a sudden and drastic drop of snow

• The biggest avalanche happened on Mt. Huascaran killing 20,000

Landslides

• A landslide or a landslip is a movement in the ground and a shallow flow of debris.

• The largest landslide in history happened because of Mount St. Helens. 3km of rock moved downhill.

Unusual Natural Disasters

• Firenadoes • Limnic Eruptions

Firenadoes

• A firenado is a column of smoke and fire caused when fire gets into a tornado.

• Firenadoes are also known as firewhirls, fire devils and fire tornadoes

Limnic Eruptions

• A limnic explosion is also called a lake overturn and is caused by an explosion of gas from the lake (normally carbon dioxide) erupting and suffocating people.

• There are only three exploding lakes. They are Lake Menoun, Lake Nyos and Lake Kivu

Limnic Eruptions

• The biggest eruption ever recorded is Lake Nyos killing 1800 people and many animals.

• The biggest danger is Lake Kivu which would cause a methane explosion and kill around 2 million.

• Interestingly all these lakes are in Africa and both Menoun and Nyos are in Cameroon.

Man made disasters

An man made disaster is a threat having an element of human intent, negligence, or error, or involving a

failure

List of few man made disasters

• The nuclear bombing • Terrorism • Oil spill

The atomic bombing • The first two atomic bomb were used by the

USA to end the war against Japan in 1945. • The first one was called Little Boy and dropped

by a flight called Enola Gay on Hiroshima with a death toll of around 166,000 on 6 August 1945.

• The second was named The fat man and was dropped by a plane called Bockscar on Nagasaki with a death toll of around 80,000 on 9 August 1945.

• If Japan did not surrender the USA planned too continue dropping atomic bombs until they did.

Terrorism

• 9/11 is the big act of terrorism on US • On September 11th, 2001, 4 flights were hi-

jacked 2 of them hit the twin towers in New York and third flight hit pentagon, in Washington DC killing

• 4th flight, passengers attacked the hi-jackers and crashed the flight down.

• 4th flight was believed to have a target of White house or the Capitol.

Deepwater Horizon oil spill

• The oil spill flowed for 3 months without being stopped.

• About 780,000m3 oil is estimated to have flowed out

• 17 people were killed in the explosion that released the oil.