Published on: Mar 3, 2016
Transcripts - natural disters
Natural disasters tornado. A natural disaster is the effect of a natural hazard that affects the environment, and leads to financial, environmental and/or human losses. The resulting loss depends on the capacity of the population to support or resist the disaster, and their resilience A tornado results from a thunderstorm. They are violent, rotating columns of air blown between 50 and 300+ mph. Tornado's are usually in the shape of a funnel with a narrow end. They are extremely destructive. The word tornado comes from the Spanish word 'turned' which came from the Latin word torqueo which means 'twist'. Tornadoes normally rotate anticlockwise in the northern hemisphere. Tornados are formed where warm moist air meets cold air meets dry air. These circumstances don't always produce tornados though. Most tornadoes last for less than 10 minutes.
TSUNAMI <ul><li>A natural disaster is the effect of a natural hazard (e.g. flood, tornado , volcano eruption , earthquake , or landslide ) that affects the environment, and leads to financial, environmental and/or human losses. </li></ul><ul><li>is a series of water waves (called a tsunami wave train  ) that is caused by the displacement of a large volume of a body of water , such as an ocean . The original Japanese term literally translates as " harbor wave ." Tsunamis are a frequent occurrence in Japan; approximately 195 events have been recorded.  Due to the immense volumes of water and energy involved, tsunamis can devastate coastal regions. Casualties can be high because the waves move faster than humans can run. </li></ul>
Earthquake <ul><li>An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. </li></ul><ul><li>Earthquakes are recorded with a seismometer, also known as a seismograph. </li></ul><ul><li>The moment magnitude of an earthquake is conventionally reported, with magnitude 3 or lower earthquakes being mostly imperceptible and magnitude 7 causing serious damage over large areas. Intensity of shaking is measured on the modified Mercalli scale. </li></ul><ul><li>- </li></ul>
Hurricane <ul><li>A hurricane is a powerful, swirling storm that begins over a warm sea. Hurricanes form in waters near the equator, and then they move toward the poles. </li></ul><ul><li>Hurricanes are referred to by different labels, depending on where they occur. They are called hurricanes when they happen over the North Atlantic Ocean, the Caribbean Sea, the Gulf of Mexico, or the Northeast Pacific Ocean. Such storms are known as typhoons if they occur in the Northwest Pacific Ocean, west of an imaginary line called the International Date Line. Near Australia and in the Indian Ocean, they are referred to as tropical cyclones. </li></ul><ul><li>Hurricanes are most common during the summer and early fall. In the Atlantic and the Northeast Pacific, for example, August and September are the peak hurricane months. Typhoons occur throughout the year in the Northwest Pacific but are most frequent in summer. In the North Indian Ocean, tropical cyclones strike in May and November. In the South Indian Ocean, the South Pacific Ocean, and off the coast of Australia, the hurricane season runs from December to March. Approximately 85 hurricanes, typhoons, and tropical cyclones occur in a year throughout the world. In the rest of this article, the term hurricane refers to all such storms. </li></ul>
Volcanic eruptions <ul><li> An eruption begins when pressure on a magma chamber forces magma up through the conduit and out the volcano's vents. The type of eruption partly depends on the amount of gases and silica in the magma. The amount of silica determines how sticky the magma is and water provides the explosive potential of steam . </li></ul><ul><ul><li>When magma reaches earth's surface it is called lava. Rocks ripped loose from the inside of the volcano or torn apart by the gas may be shot into the air with the lava. These rocks blown out of a volcano are called pyroclastic rocks. The rock fragments fall back to earth in many different shapes and sizes: </li></ul></ul><ul><ul><li>Dust - particles less than 1/100 inch in diameter. Dust particles may be carried great distances. In a powerful eruption they may be carried around the earth several times. Ash - fragments less than 1/5 inch in diameter. Most volcanic ash falls to the surface and cemented together by water to form a rock called volcanic tuff. Bomb - A rounded piece of newly hardened lava which takes shape while flying through the air. Block - A piece of lava that has sharp corners. Cinder - Bubbly rock formed by liquid lava cooling in the air. Pumice - Cinder so bubbly that it floats in water. </li></ul></ul><ul><li>Volcanic activity is classified by hoy often a volcano erupsts. A volcano may be active, intermittent, dormant or extinct. Active volcanoes erupt constantly.Intermittent volcanoes erupt fairly regularly. Dormant volcanoes are inactive, but not long enough to determine whether they will erupt again or not. Extinct volcanoes have been inactive since the beginning of recorded history. </li></ul><ul><li> </li></ul>
Floods <ul><li>A flood is an overflow or accumulation of an expanse of water that submerges land.In the sense of "flowing water", the word may also be applied to the inflow of the tide. Flooding may result from the volume of water within a body of water, such as a river or lake, which overflows or breaks levees, with the result that some of the water escapes its usual boundaries.While the size of a lake or other body of water will vary with seasonal changes in precipitation and snow melt, it is not a significant flood unless such escapes of water endanger land areas used by man like a village, city or other inhabited area. </li></ul><ul><li>Principal types </li></ul><ul><ul><li>Riverine: Slow kinds: Runoff from sustained rainfall or rapid snow melt exceeding the capacity of a river's channel. Fast kinds: include flash floods resulting from convective precipitation (intense thunderstorms) or sudden release from an upstream impoundment created behind a dam, landslide, or glacier. </li></ul></ul><ul><ul><li>Estuarine:Commonly caused by a combination of sea tidal surges caused by storm-force winds. </li></ul></ul><ul><ul><li>Coastal:Caused by severe sea storms, or as a result of another hazard . </li></ul></ul><ul><ul><li>Catastrophic:Caused by a significant and unexpected event, or as a result of another hazard </li></ul></ul><ul><ul><li>Muddy:A muddy flood is produced by an accumulation of runoff generated on cropland. </li></ul></ul><ul><li> </li></ul>
AVALANCHES An avalanche is a rapid flow of snow down a slope, from either natural triggers or human activity. Typically occurring in mountainous terrain, an avalanche can mix air and water with the descending snow. Powerful avalanches have the capability to entrain ice, rocks, trees, and other material on the slope; however avalanches are always initiated in snow, are primarily composed of flowing snow, and are distinct from mudslides, rockslides,rock avalanches, and serac collapses from an icefall .