Nature strikes back...

Through the earth, water and air:

When Mother Nature is not treated right she naturally strikes back in various forms. The number of natural disasters seem to be on the increase these days. The experts claim, global warming which we humans are also responsible for, is a major contributory factor for the extreme weather conditions we are experiencing presently.

Earthquakes, tsunamis and lightning strikes are three forms of natural phenomena that are in the news these days following the recent incidents experienced in the country. Most of us experienced the earth tremors that were felt in Sri Lanka following the massive earthquake which struck the Ache region in Indonesia in the Indian Ocean in April.

The tsunami warning which was issued following the quake pressed a panic button with people scrambling for safety,especially those living along the coastal areas of the country. 

Even though most of you would not know the impact of an earthquake, some of you are bound to be familiar with the destructive force of a tsunami because of the massive tsunami that left millions dead in a number of countries including Sri Lanka in the Indian Ocean in 2004.Unlike earthquakes and tsunamis which are rather predictable, the other natural phenomenon we are constantly asked to be careful of is lightning.

During the past few weeks much property has been damaged and many lives lost including those of animals as a result of severe lightning; a common occurrence during the Monsoon rains.

We may not have the power to stop any one of these destructive forces from taking place, but we certainly can take preventive measures to minimise their impact, if and when they do occur.

So,always try to familiarise yourselves with the numerous types of natural disasters that impact the world in general and Sri Lanka in particular and keep in mind the safety measures we should follow in the event such a disaster should strike. Remember , it was the lack of knowledge about what a tsunami is that led to the loss of millions of lives in 2004. Had we known about it we would have taken safety measures just like we did when the tsunami alert was issued on April 11. We take this opportunity to salute all those who were instrumental in ensuring the safety of the people during the recent tsunami threat by alerting them and guiding them to safer areas.

Today we feature some valuable information about earthquakes, tsunamis and lightning; three main ways Mother Nature strikes back from deep within the earth, through water and from the air. These natural disasters could happen any day, anytime,anywhere. So be on the alert, always!

Tsunamis

What is a tsunami?

 A tsunami is a series of great sea waves caused by an underwater earthquake, landslide, or volcanic eruption, tsunami (pronounced soo-NAH-mee) is a Japanese word. Tsunamis are fairly common in Japan, and many thousands of Japanese have been killed by them in recent centuries.Tsunamis cause damage by two mechanisms: the smashing force of a wall of water travelling at high speed, and the destructive power of a large volume of water draining off the land and carrying all with it, even if the wave does not look large.

What causes a tsunami?

 An earthquake generates a tsunami if it is of sufficient force and there is violent movement of the earth to cause substantial and sudden displacement of a massive amount of water. However, a tsunami is not a single wave but a series of waves, also known as a wave train. The first wave in a tsunami is not necessarily the most destructive. Tsunamis are not tidal waves.

How huge are tsunamis?

A tsunami may be less than a foot (30 centimetres) in height on the surface of the open ocean at times, which is why they are not noticed by sailors. But the powerful shock wave of energy travels rapidly through the ocean as fast as a commercial jet. Once a tsunami reaches shallow water near the coast, it is slowed down. The top of the wave moves faster than the bottom, causing the sea to rise dramatically. Tsunami waves can be very long (as much as 60 miles, or 100 kilometres) and be as far as one hour apart. They are able to cross entire oceans without great loss of energy.

The Indian Ocean tsunami travelled as much as 3,000 miles (nearly 5,000 kilometres) to Africa, arriving with sufficient force to kill people and destroy property. Where the ocean is deep, tsunamis can travel unnoticed on the surface at speeds up to 500 miles an hour (800 kilometres an hour), crossing an ocean in a day or less. Scientists are able to calculate arrival times of tsunamis in different parts of the world based on their knowledge of water depths, distances, and when the event that generated them occurred.

 Geological features such as reefs, bays, river entrances, and undersea formations may dissipate the energy of a tsunami. In some places a tsunami may cause the sea to rise vertically only a few inches or feet. In other places tsunamis have been known to surge vertically as high as 100 feet (30 metres). Most tsunamis cause the sea to rise no more than 10 feet (3 metres).

How to stay safe

A tsunami cannot be precisely predicted, even if the magnitude and location of an earthquake is known. Sometimes, but not always, the tsunami’s arrival is preceded by a noticeable withdrawal of the water.

However, as soon as a tsunami warning is given move to higher ground. Do not wait to collect your belongings if there is very little time to get to higher ground.

If the closest highest point you can get to is a building, first make sure it is sturdy to withstand the force of the wave. Do not rush into any high rise building without making sure how strong the structure is.

Earthquakes

What is an earthquake?

The sudden release of energy in the Earth’s crust that creates seismic waves is known as an earthquake. In its most general sense, the word earthquake is used to describe any seismic event — whether natural or caused by humans — that generates seismic waves.

Earthquakes are caused mostly by rupture of geological faults, but also by other events such as volcanic activity, landslides, mine blasts, and nuclear tests. An earthquake’s point of initial rupture is called its focus or hypocentre.

The epicentre is the point at ground level directly above the hypocentre. An earthquake is also called a quake, tremor or tembler.

The seismicity, seismism or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time.

At the Earth’s surface, earthquakes manifest themselves by shaking and sometimes displacement of the ground. When the epicentre of a large earthquake is located offshore, the seabed may be displaced sufficiently to cause a tsunami. Earthquakes can also trigger landslides, and occasionally volcanic activity.

What are the types of earthquakes?

There are many different types of earthquakes: tectonic, volcanic, and explosion. The type of earthquake depends on the region where it occurs and the geological make-up of that region. The most common are tectonic earthquakes.

These occur when rocks in the Earth’s crust break due to geological forces created by movement of tectonic plates. Another type,volcanic earthquakes, occur in conjunction with volcanic activity. Collapse earthquakes are small earthquakes in underground caverns and mines, and explosion earthquakes result from the explosion of nuclear and chemical devices.

How are earthquakes measured?

 Earthquakes are measured using observations from seismometres. The moment magnitude is the most common scale on which earthquakes larger than approximately 5 are reported for the entire globe.

Earthquakes smaller than magnitude 5 reported by national seismological observatories are measured mostly on the local magnitude scale, also referred to as the Richter scale. These two scales are numerically similar over their range of validity.

Magnitude 3 or lower earthquakes are mostly almost imperceptible and magnitude 7 and over potentially cause serious damage over large areas, depending on their depth. 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

What is the largest earthquake recorded so far?

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.

What are aftershocks?

An aftershock is an earthquake that occurs after a previous earthquake, the main shock. An aftershock is in the same region of the main shock but always of a smaller magnitude.

If an aftershock is larger than the main shock, the aftershock is redesignated as the main shock and the original main shock is redesignated as a foreshock. Aftershocks are formed as the crust around the displaced fault plane adjusts to the effects of the main shock.

What are earthquake storms?

Sometimes a series of earthquakes occur in a sort of earthquake storm, where the earthquakes strike a fault in clusters, each triggered by the shaking or stress redistribution of the previous earthquakes. Similar to aftershocks but on adjacent segments of fault, these storms occur over the course of years, and some of the later earthquakes are as damaging as the early ones.

Such a pattern was observed in the sequence of about a dozen earthquakes that struck the North Anatolian Fault in Turkey in the 20th century.

How to stay safe

Stay calm. Panicking will only make you do all the wrong things in an emergency.

If your home or office is located inside a multistory building,be alert to the possibility of structural collapse. Never seek shelter under glass tables.

Seek cover under furniture only if they are built of sturdy materials. Keep away from windows; these can shatter and injure you.

Stay away from heavy mirrors or any heavy furniture like file cabinets,bookcases and cupboards and heavy objects hanging from the ceiling. Watch out for falling plaster and debris.

If the shelter you found does withstand the pressure of falling debris do not leave it If the object moves for the shaking move with it. Stay inside until the shaking stops and it is safe to go outside.

If you are outdoors when it strikes move away from buildings, trees and utility wires and get to an open area without anything overhead .

If you’re driving while an earthquake hits, stop your vehicle and stay in your car, but make sure to stay away from trees bridges, overpasses, buildings, and utility wires.

Lightning

What is lightning?

Lightning is one of the oldest observed natural phenomena on Earth. It has been seen in volcanic eruptions, extremely intense forest fires, surface nuclear detonations, heavy snowstorms, in large hurricanes, and obviously, thunderstorms.

Lightning is a gigantic electrostatic discharge between the cloud and the ground, other clouds, or within a cloud. Scientists do not understand yet exactly how it works or how it interacts with the upper atmosphere or the Earth ‘s electromagnetic field.

What causes lightning?

The creation of lightning is a complicated process. Lightning is an electric current, and just like the electricity lurking in the outlets in your house, it can be deadly. Within a thundercloud, many small bits of ice bump into each other as they swirl around in the air. All those collisions create an electrical charge.

After a while, the whole cloud fills up with electrical charges (usually with a negative charge closest to the Earth). Since opposites attract each other, that causes a positive charge to build up on the ground beneath the cloud. The ground’s electrical charge concentrates around anything that sticks up, such as mountains, lone trees, people, or even blades of grass. The charge streaming up from these points eventually connects with a charge reaching down from the clouds, and lightning strikes.

The intense heat of the lightning bolt causes the surrounding air to explode outward with a gigantic boom - -thunder.

How much lightning is there?

Lightning flashes aren’t all the same shape or size, and they don’t all carry the same amount of electrical current. And two clouds that are about the same size may create very different amounts of lightning. It depends on how much electrical charge the cloud has, and that depends on a lot of other things, like how fast air is moving in the cloud and how many ice crystals have formed in the cloud.

How to stay safe

Lightning is dangerous.Stay away from it. Lightning kills .Many deaths have been recorded in the country during the past few weeks.

The best way to keep from getting struck by lightning is to go inside before an electrical storm gets too close. To find out how close the storm is, start counting slowly as soon as you see lightning. Light travels extremely fast, so the lightning’s flash reaches your eyes instantly, but the sound of thunder travels much slower--one mile in five seconds. If you hear thunder before you can count to 30, the storm is within six miles of you, and the next lightning strike could be right near you. Get into a house or car and stay there till the storm moves away.

If you’re not close to shelter, here are some things to stay away from:

*Tall trees or poles
*Completely open areas like fields
*Bodies of water, like lakes or the ocean
*Metal fences and equipment, sports equipment and bikes

* Stay at least a few feet away from open windows, sinks, toilets, tubs, showers, especially electrical boxes , outlets and appliances which are plugged in. Lightning can flow through these electrical items and “jump” to a person.

*Do not shower or take a bath during a thunder or lightning storm,especially in open areas.

* Avoid using regular telephones, except in an emergency. If lightning hits the telephone lines, it could flow to the phone. Cell or cordless phones, not connected to the building’s wiring, are safe to use. Facts and pix:Internet