Danger of Tsunami

November 04, 2009 - Tsunami becomes one of the dangerous natural disasters in the world. Every one should aware of the Tsunami.

The phenomenon we call a tsunami is a series of waves of extremely long wavelength and period generated in a body of water by an impulsive disturbance that displaces the water. Although tsunamis are often referred to as "tidal waves" by English-speaking people, they are not caused by the tides and are unrelated to them.

Tsunamis are primarily associated with earthquakes in oceanic and coastal regions. When an earthquake occurs, the energy travels outward in all directions from the source. This can be illustrated by throwing a pebble into a small, still pond. The pebble represents a meteorite or some other energy source, and the pond represents the ocean. The ripples that travel out in all directions from the focus, or the point where the pebble hit the water, represent the energy that creates a sea wave. Notice how the waves become larger as they reach shore, where the water is shallower.

Detecting tsunamis is a very difficult thing to do. When a wave begins in the deep ocean waters, it may only have a height of about twelve to twenty-three inches and look like nothing more than the gentle rise and fall of the sea surface. An example of how easy tsunamis are to overlook is the Sanriku tsunami, which struck Honshu , Japan , on June 15, 1896 .

Fishermen twenty miles out to sea didn't notice the wave pass under their boats because it only had a height at the time of about fifteen inches. Twenty-eight thousand people were killed and 170 miles of coastline were destroyed by the wave that had passed under them.

Tsunamis in deep water can have a wavelength greater than 300 miles (500 kilometers) and a period of about an hour. This is very different from the normal California tube, which generally has a wavelength of about 300 feet (100 meters) and a period of about ten seconds. (The period of a wave is the time between two successive waves.)

Tsunamis are shallow water waves, which mean that the ratio between water depth and wavelength is very small. These shallow-water waves move at a speed equal to the square root of the product of the acceleration of gravity (9.8m/s/s) and the water depth. The deeper the water, the faster and shorter the wave is. For example, when the ocean is 20,000 feet deep, a tsunami travels at 550 miles per hour. At this speed, the wave can compete with a jet airplane, traveling across the ocean in less than a day.

Another important factor in considering tsunamis is the rate at which they lose energy. Because a wave loses energy at a rate inversely related to its wavelength, tsunamis can travel at high speeds for a long period of time and lose very little energy in the process.

How to Reduce Tension

November 03, 2009 - Health Tip of the day

What strategies do you use to make yourself feel better, increase your energy levels and reduce your tension? That's the question Robert Thayer and colleagues at California State University were motivated by in looking for the strategies people use and find effective (Thayer, Newman & McClain, 1994). There's no revelations in the results but the fact that the same three main strategies were useful in changing mood and reducing tension and raising energy speaks volumes:

Exercise: rated as the most effective for changing a bad mood, also good for raising energy and reducing tension.

Music: rated the second most successful way to change a bad mood, and raising energy and reducing tension. This may be a surprising finding for some people.

Social interaction: good for changing a bad mood and reducing tension although not necessarily so good for raising energy.

Apart from these main categories that were good across the board, there were other strategies that worked in a more selective fashion:

Pep talk: this was rated as most successful for energy enhancement - above both exercise and music.

Distractions (like shopping, reading, chores and hobbies): seen as useful for changing a bad mood.

At the other end of the scale, the things people rated as relatively less successful were:

TV: less effective for reducing tension

Eating: also less effective for reducing tension.

Coffee: not that good for raising energy, relative to the other categories.

Gender differences were also seen. Men are more likely to try and distract themselves or seek pleasure, while women are more likely to seek social support.