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8/7/2019 Projek English

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TSUNAMI

Tsunami are a series of waves usually generated by movement of the seafloor. These

movements are caused by different typs of geophysical phenomens such as earthquakes,

landslides, volcanic eruptions, slumps and meteroits. But 90% of the Tsunamis are initiatedwith earthquakes.They all repress a enormus mass of water, which become special waves,

the ratio between the the water depth and the length of these waves is very small. They

move at a speed equals to the square root of the product o f gravity (9,8m/s/s) and the depth

of the water. Because they lose energy reciprocally related to their lentgh, they can travel

with high speed over long distances without losing much energy. Therefore, the tsunami

reachs the coast with a destructive and devasting force.


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FLASH FLOOD

Flash flooding occurs when a barrier holding back water fails or when precipitation falls too

quickly on saturated soil or dry soil that has poor absorption ability. The runoff collects in

low-lying areas and rapidly flows downhill. Flash floods most often occur in normally dry

areas that have recently received precipitation, but may be seen anywhere downstream

from the source of the precipitation, even dozens of miles from the source. In areas on or

near volcanoes, flash floods have also occurred after eruptions, when glaciers have been

melted by the intense heat. Flash floods are known to occur in the highest mountain ranges

of the United States and are also common in the arid plains of southwestern U.S.


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EARTHQUAKE

An earthquake (also known as a quake, tremor or temblor) is the result of a sudden release

of energy in the Earth'scrust that creates seismic waves. The seismicity or seismic activity of

an area refers to the frequency, type and size of earthquakes experienced over a period of

time. Earthquakes are measured using observations from seismometers. The moment

magnitude (or the partly obsolete Richter magnitude, numerically similar over the range of

validity of the Richter scale) of an earthquake is conventionally reported, with magnitude 3

or lower earthquakes being mostly almost imperceptible and magnitude 7 and over

potentially causing serious damage over large areas, depending on their depth. The largest

earthquakes in historic times have been of magnitude slightly over 9, although there is no

limit to the possible magnitude. The most recent large earthquake of magnitude 9.0 or larger

was a 9.0 magnitude earthquake in Japan in 2011 (as of March 2011), and it was the largest

Japanese earthquake since records began. Intensity of shaking is measured on the modified

Mercalli scale. The shallower an earthquake, the more damage to structures it causes, all

else being equal.


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TORNADO

Atornado (often referred to as a twister or, erroneously, a cyclone) is a violent, dangerous,

rotating column of air that is in contact with both the surface of the earth and a

cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. Tornadoes come in many

shapes and sizes, but are typically in the form of a visible condensation funnel, whose

narrow end touches the earth and is often encircled by a cloud of debris and dust. Most

tornadoes have wind speeds less than 110 miles per hour (177 km/h), are approximately

250 feet (80 m) across, and travel a few miles (several kilometers) before dissipating. The

most extreme can attain wind speeds of more than 300 mph (480 km/h), stretch more than

two miles (3 km) across, and stay on the ground for dozens of miles (more than 100 km).

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