Monday, March 22, 2010

Dasam falls a tragic picnic spot in Jharkhand State of India. Rocks structure plays major role.

Geological factors may be responsible for such accidents.
Potholes present in the rocks are dangerous.
by
Dr. Nitish Priyadarshi

Waterfalls offer breathtaking views and are cool places to relax and feel the astounding beauty and benefits of nature. But in some cases, these wonderful gifts of nature to mankind bring tragedy to people.

A fun filled day out at the famous Dasam falls, near Ranchi city, proved fatal for four youngsters. They drowned while enjoying a picnic on Saturday (20th March).

This is not the new case. Every year many people die in this fall especially from November to March. Causes of deaths were due to drowning.

The Dasam (meaning ten) falls also known as Dasomghagh, 40 Kms south-east of Ranchi city near Taimara valley is formed by the Kanchi river falling over a ledge of a rock in a sheer descent of 114 feet amid rocky and sylvan scenery.

There are different mythological stories behind such accidental deaths. But no scientific investigations have been done to know the exact cause of sudden drowning.

I have tried to point out some geological factors which may be responsible for such accidents.

In spite of great falls like Hundru and Jonha deaths occurs only in Dasam falls. Geological cause behind this is the rock structures. Surface rocks surrounding the area are highly smooth. This is due to abrasion. Abrasion is the mechanical scraping of a rock surface by friction between rocks and moving particles during their transport by wind, glacier, waves, gravity, running water or erosion. This phenomenon is active there from millions of years. People wearing leather shoes or slippers are more prone to accident on this polished surface. There are more chances for the people of getting slipped inside the water and injuring their heads.

Other major factor responsible for such accidents is the presence of pot holes. Many pot holes are found in the river beds in Jharkhand state. Jharkhand rocks favor such formations. Some are such large that even the elephants can also be trapped especially in the Palamau area.
Potholes are usually regarded as one of the erosional features. The traditional interpretation is in terms of the process of abrasion of the bedrock by rotary currents inside the potholes, and vibration of pebbles and stones by the water, that gradually wore the holes deeper and deeper into the bedrock.

In the usual interpretation, potholes are considered to be the effects of erosion by streams and rivers over very long periods of time. The actual work of abrasion is considered to have been done either by hard grains of sand held in suspension by the rapidly flowing water; or by large boulders, called "grinders," in the bottom of the pothole, that were agitated constantly by the currents swirling around inside.

Strong under currents is generated when water enters such pot holes. These currents act as suction pump. When people enter in water there are more chances to get trapped and pulled inside. State government must flag such dangerous potholes in Dasam falls and people must be warned of such areas.

Even the crevices or the long gaps present in the rocks beneath the water are dangerous. People entering the water are unaware of such crevices or gaps between the rocks. They are the silent killers. Rocks around such falls in Ranchi district are filled with crevices and depressions.

As Dasam falls is flooded with people during the season, it is more prone to such accidents. Rocks beneath the water and surrounding play a major role to make this spot picturesque. But they also act as killer stone.
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