Post on 08-Apr-2018
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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).