Tsunami - a seismic sea wave - means in Japanese "harbor-wave". It is also misleadingly called "tidal wave". It is an ocean wave caused by an earthquake of magnitude 6.5 on Richter scale (or greater) that occurs less than 50 kilometers beneath seafloor. Tsunamis can also be caused by volcanic eruptions and by landslides.

Tsunami waves are followed by three to five oscillations of continental shelf waters. These convulsions may last up to a week. If initial wave reaches shore at its trough phase, water recede and expose seafloor. This happened in Lisbon Port on November 1, 1755. A few minutes later, displaced waters return with energetic vengeance.

In ocean, tsunami waves are merely 0.5-2 meters high with a wavelength of up to 200 kilometers. Consequently, they are virtually impalpable though they move at speeds of up to 700 kilometers per hour. As waves near shoreline, friction with shallow bottom reduces their velocity, shortens their wavelength, increases their amplitude and their height.

The tsunami wave that swept across coasts of Indonesia, Sri Lanka, Thailand, India, and Africa on December 26, 2004 was 10-12 meters high. It traveled almost 6000 kilometers. It killed almost 150,000 people. An earthquake in fjord-like Lituya Bay, Alaska, on July 9, 1958, generated a tsunami wave 524 meters (1719 feet) high, moving at a speed of 160 kilometers per hour. Luckily, area was largely uninhabited.

Other notable tsunamis:

In 1703 at Awa, Japan with more than 100,000 people dead.

On April 24, 1771, a tsunami caused by an underwater earthquake struck Japanese island of Ishigaki (in Ryuku chain). It was 85 meters high. It was so powerful that it hurled a 750 ton piece of coral to a distance of 2.5 kilometers inland.

Again in Japan, 27,000 people drowned in 1896, in a giant tsunami.

In wake of underwater volcanic eruptions that obliterated island of Krakatau (Krakatoa) on August 26-27, 1883, a wave 35 meters high swept across East Indies killing in excess of 36,000 people.

Triggered by a submarine landslide, a tsunami at least 375 meters high struck island of Lanai in Hawaii about 105,000 years ago.

The 1960 earhquake in Chile created tsunami waves that traveled more than 10,000 kilometers to Hilo, Hawaii. The 12 meters high water wall killed 61 people and destroyed many buildings.

The Seismic Sea Wave Warning System (SSWWS), based in Honolulu, is an early warning system covering entire, tsunami-prone, Pacific Ocean.

Earthquakes

Little known facts about temblors:

The epicenter of an earthquake is not same as its hypocenter (focus, point of origin within a fault-line). The epicenter is point on surface of Earth directly above focus. Dangerous, shallow-focus quakes originate 0-70 kilometers below surface. Less damaging deep-focus tremors occur between 70-700 kilometers down. Subduction zone earthquakes (like one that gave rise to lethal tsunami on December 26, 2004) occur when one tectonic plate moves under another (subducts). There are interplate and intraplate quakes, which take place along plate boundaries or within fracturing crust of a single plate, respectively.

Earthquakes are not rare at all - several hundred earthquakes occur every day. There are about 1 million of them annually - of which 50,000 can be felt without aid of instruments. Tremors of magnitude of Kobe in 1995 (which caused an estimated damage of $100 billion ) are measured 20 times in an average year.

The Encyclopedia Britannica (2005 edition) describes a "swarm" of such events thus:

"In Matsushiro region of Japan, for instance, there occurred between August 1965 and 1967 a series of hundreds of thousands of earthquakes, some sufficiently strong (up to local magnitude 5) to cause property damage but no casualties. The maximum frequency was 6,780 small earthquakes on April 17, 1966."

The Pacific ocean is unhappy recipient of well over 80 percent of all energy released by earthquakes worldwide. Japan alone suffers from 1500 tremors annually (of which two thirds are greater than 3.5 in magnitude). Fault lines abound and new ones are discovered frequently. One fault line runs under 125th street in Manhattan, New-York.

Still, in last 5 centuries, all earthquakes combined killed less than one tenth victims of World War II - and this includes 240,000 who died in 1976 Tang-Shan, China event.

Earthquakes are composites of:

I. Primary (or compression) and secondary (or shearing) body waves (that travel in rocks under surface of Earth at speeds of up to 7 kilometers per second and frequencies of between 20 Hertz and one vibration per 54 minutes)

and

II. Two types of surface waves, named after British physicist Lord Rayleigh and British geophysicist A. E. H. Love (with frequencies of 1-0.005 Hertz).

What if someone were to come into your lovely shining home and mix up a cocktail of unknown chemicals for you and your family to distribute around house. Would you allow it? Of course not. You wouldn’t want potentially poisonous chemicals around your house to pose a risk of contamination to air you breath or to what your family eat & drink.

Disturbingly however, they may already be there.

Brought into your home as unseen and unlabelled additives in many of cleaning products that are commonly available to keep your house sparkling clean.

You may think that ingredients in household products are safe having been tested by authorities and cleared for use because they are known to pose no threat. Sadly, nothing could be further from truth.

In reality many hazardous chemicals are added to consumer goods. Some of these are known to be hazardous, but current legislation allows for their continued use. This is because regulations work on ‘safe limits’ of exposure for individual products. The weaknesses of this approach are that they do not add up accumulated doses from multiple sources of exposure, and neither do they take into account effect on children and unborn infants, dosages allowed being based on adult tolerance levels.

A study by European Environment Agency carried out in 1998 noted that ”widespread exposures to low levels of chemicals may be causing harm, possibly irreversibly, particularly to sensitive groups such as children and pregnant women…”

Consider some of these common types of household cleaning product and what threat they may carry.

Air Fresheners

Many of these products contain formaldehyde and phenol. The former is a known carcinogen and later can cause skin irritation.

Antibacterial Cleaners

May contain triclosan, which has been connected to liver damage and is readily absorbed through skin

Carpet and upholstery shampoo

Many contain perchlorethane, which is a carcinogen which damages liver, kidneys and central nervous system. Ammonium hydroxide may also be present which is a corrosive compound, extremely irritating to eyes, skin and respiratory system.

Dishwasher detergents

Studies have shown these to be foremost cause of home poisoning incidents. Most products contain dry form of chlorine. Scientists and engineers do not handle chlorine without protective clothing. It is extremely dangerous and can very easily be lethal. Indeed, it was first agent to be used in World War One as a chemical warfare agent.

Dishwashing liquids are labelled ‘harmful if swallowed’ yet it is used to wash your dishes. Can we be certain that no residues are left on your crockery to be picked up by your food?

Furniture polish

Commonly contain nitrobenzene, which is highly toxic and easily absorbed through skin. Petroleum distillates may also be present, which are highly flammable and have been linked to skin & lung cancer.

Laundry products.

These present a veritable cocktail of chemicals, including ammonia, phosphourous, naphthalene & phenol along with numerous others. They can all cause irritation to skin, allergies and sinus problems. Any residue left in your clothes can be absorbed into your body through skin.

Oven cleaner

These are most powerful toxic products that you can introduce into your home. They contain ammonia and other chemicals which can irritate skin, and produce fumes which can attack respiratory system. Any residue left in your oven may be intensified when you next use it.

Toilet cleaner

These usually contain hydrochloric acid which is highly corrosive, eyes and skin being particularly vulnerable to attack, and known to be harmful to liver and kidneys. If mixed with other chemical products, chlorine can be produced which can be fatal in high concentrations.

The above is a brief overview of possible risks, and it must be stressed that effects noted for individual chemicals are for high levels of exposure. However, point being made by many agencies such as Greenpeace is that level of exposure in home is unknown and unmonitored.

What can you do as a householder to minimise risk to yourself and your family? Well, if you are able, you may want to try talking to your grandmother, as past generations have had to undertake most modern cleaning tasks without intervention of chemical industry. For instance, she may have used common salt and baking soda to clean oven and not risk poisoning anyone.

The easiest way to avoid risk is to avoid products. Governments are not going to outlaw chemicals, and manufacturers are not going to replace them unless they are forced to do so, either by regulation or by consumer pressure.