LIJA DINESHCLASS NO: 29NATURAL SCIENCEM.G.U.C.T.E

DISASTER THEIR IMPACT ON THE ENVIRONMENT

A disaster is a sudden, calamitous event

Seriously disrupts the functioning of a community or society

Causes - human, material, and economic or environmental losses

Exceed the community’s or society’s ability to cope using its own resources.

Caused by natural and man made orgins

NATURAL DISASTERS

A natural disaster is a major adverse event resulting from natural processes of the Earth.

A natural disaster can cause loss of life or property damage, and typically leaves some economic damage.

SOME OF NATURAL RESOURSES

FOREST FIRE

FLOOD

EARTH QUAKE

TSUNAMI

FOREST FIREA forest fire is an uncontrolled fire occurring in nature

Many as nine out of ten forest fires are caused by humans .

The four major natural causes of wildfire ignitions are

Lightning, Volcanic eruption, Sparks from rock falls, Spontaneous combustion.

The most common human sources of wildfires

Arson Discarded cigarettes Sparks from equipment Power line arcs

EFFECT OF FOREST FIRE Loss of valuable timber resources

Loss of wildlife habitat and depletion of wildlife Loss of natural regeneration and reduction in forest cover Ozone layer depletion

Soil erosion affecting productivity of soils and production

Health problems leading to diseases,

FLOOD It is a natural event or occurrence where a piece of land (or area) that is usually dry land, suddenly gets submerged under water. Some floods can occur suddenly and recede quickly.

Others take days or even months to build and discharge.

When floods happen in an area that people live, the water carries along objects like houses, bridges, cars, furniture and even people.

It can wipe away farms, trees and many more heavy items.

WHAT CAUSES FLOODING?

River overflow

Strong winds in coastal areas

Dam breaking

Ice and snow-melts

TYPES OF FLOODS Flash floods This kind occurs within a very short time (2-6 hours, and sometimes within minutes) and is usually as a result of heavy rain, dam break or snow melt.

Rapid on-set floods

Similar to flash floods, this type takes slightly longer to develop and the flood can last for a day or two only.

Slow on-set floods

This kind is usually as a result of water bodies over flooding their banks.

They tend to develop slowly and can last for days and weeks

EFFECTS OF FLOODINGFloods can have devastating consequences and can have effects on the economy, environment and people.

ECONOMIC During floods (especially flash floods), roads, bridges, farms, houses and automobiles are destroyed.

People become homeless.ENVIRONMENT

The environment also suffers when floods happen.

Chemicals and other hazardous substances end up in the water and eventually contaminate the water bodies

PEOPLE AND ANIMALS Many people and animals have died in flash floods

Flooding brings a lot of diseases and infections including military fever, pneumonic plague, dermatopathia and dysentery.

Floodwaters carry lots of nutrients that are deposited in the plains.

Farmers love such soils, as they are perfect for cultivating some kinds of crops.

BENEFIT OF FLOOD

Earthquakes are the rumblings, shaking or rolling of the earth's surface.

It is usually what happens when two blocks of the earth suddenly slip past one another,

Or break apart from each other as a result of tension caused by prolonged energy build up.

Earthquakes are also called temblors.

It is important to understand the earth’s makeup to help understand earthquakes better.

The outer is the crust, which is the hard part of the earth that forms the surface. This outer crust includes the land on which we live, the oceans and ocean deeps

Earthquakes are developed in the outer crust of the earth

THE TYPES OF EARTHQUAKES Earthquakes can come in three main forms, depending on the plate movements that occur beneath the earth's surface.

They could occur on a Convergent Boundary, Divergent Boundary or a Transform Fault

CONVERGENT BOUNDARY One plate is forced over another plate during movement creating a thrust fault. DIVERGENT BOUNDARY Plates are forced apart each other, usually forming a Rift Zone. This kind is common in ocean floors where new floors are created.

TRANSFORM FAULTUnlike divergent and convergent, the plates here slip by each other. This is also called Strike-Slip.

There are 2 types of earthquakes waves

These are waves of energy that travel through the earth's layers, and other elastic layers, often as a result of earthquakes.

A wave, by general definition is the transfer of energy from one place to another without transferring solid, liquid or gas matter. Examples include light and sound waves.

During an earthquake, the waves released may be “P” or “S” waves depending on the speed and ways in which they travel.

EARTHQUAKE WAVES

P-Waves (Primary Waves)

P-waves are longitudinal in nature. The vibrations are along the same direction as the direction of travel. It is also known as compressional waves. P-waves travel faster than S-waves.

S-Waves (Secondary waves)

Here the waves travel at right angles to the direction of travel. They are also known as transverse waves and example include water waves.

Collapsing buildings, walls, bridges, falling furniture or objects, shattering glass windows and mirrors.

Falling electricity lines

Rock slides and/or landslides on mountains and hillsides.

Floods caused by the collapse of dam walls.

Tsunamis.

EFFECT OF EARTHQUAKE

Building and other structures sink into the ground or overturn and buried tanks and other cavities rise to the surface. This is known as liquefaction.

LIQUEFACTION. When sediments with a high water content are subjected to prolonged shaking, the pressure of the water held in pores in the sediment graudally increases eventually, the sediments lose all cohesive strength and begin to behave as if they were liquids.

TSUNAMI

A series of massive ocean waves, triggered by an earthquake that has occurred in the sea (or ocean).

The displaced water then runs ashore and into the land.

This happens when the plates underneath the Earth's surface move (focus) so that one slips under another.

Tsunamis may also be caused by underwater landslides or volcanic eruptions

Researchers believe that most tsunamis, (80%), happen within the Pacific Ocean’s “Ring of Fire,” a geologically active area where tectonic shifts make volcanoes and earthquakes common.