A .36-km-long crack that has appeared on the left bank of the Ghaggar in Nada (Panchkula) has thrown up a gamut of questions to geologists.

As they grapple with them, the site has been a scene of hectic activity since the crack was first noticed on March 5. Geologists with their thinking caps on, have been surveying the entire area, in search of answers. They have been scaling the height of the hillock where chunks of rock have subsided, wheras the low-lying fields nearby have experienced a rise of nearly 20 cm on an average.

The area near the Nada choe, put on the world map with this activity, has had experts coming not only from the region but also from foreign countries. These foreign geologists were incidentally in the country to attend an international conference.

Though the crack is being described as a ``natural phenomenon'', common in the Himalayan belt, it has generated a lot of interest by virtue of its surficial expression, an occasion rare enough for geologists to ponder over. The crack runs across the hillock, the Ghaggar river bed and the fields situated on the opposite bank.

Experts point out that such activity, though common, can hardly ever be seen, let alone with the naked eye.``These fissures and cracks usually happen below the soil covering the crust of the earth. The only clue of their occurrence is the recording of shockwaves of very low intensity, which are released from the surface. This is, indeed, one in a million chance for of us,'' explains Dr GSGill of the Centre of Advanced Study in Geology (CASG), Panjab University (PU), who was one of the first few geologists to reach the spot.

While the studies oscillate between establishing the fact whether the crack is a consequence of seismic activity or not, the Haryana Urban Development Authority (HUDA) finds itself on the horns of a dilemma with prima facie evidence pointing that the immediate area in the vicinity of the crack is unfit for construction purposes, irrespective of the findings of experts.

The HUDA authorities, however, remain tight-lipped about the fate of the land acquired from farmers for construction of housing societies. ``We will be able to get a clear picture only once the findings of geologists come in. Nothing can be based on preliminary reports and we are willing to wait and watch till the final verdict, which may take many months or even a year, comes, informs the Chief Engineer, HUDA, KKBhugra.

While roping in geologists from elsewhere in the country, HUDAis hoping for a miracle. The geologists, however, are mincing no words in declaring the area unsuitable for construction purpose.

Geologists say that any habitation in the area where the crack has surfaced could be wiped clean. ``If, at any point of time, construction is given the ``go ahead'' signal, activity beneath the surface could present a threat to life and property,'' claims Prof LNGupta from the CASG, PU.

Echoing similar views, senior geologist from the Geological Survey of India (GSI), GCBhambry, says: ``My first advice to HUDA would be to just lay off the piece of land unless it is absolutely essential. In case HUDAcannot do without the sale of land, a number of precautionary measures would need to be adopted while ensuring that the plan does not take into account the affected patch.''

Meanwhile, reports of research work carried out at the site by the CASG and the GSI have been submitted to the district administration. Ironically, the two contradict each other when it comes to disclosing the cause of the crack—the CASG states the crack was a result of neo-tectonic activity which could be seismic or aseismic in nature, while the GSI suggests that it was a consequence of circular failure of the rock mass due to water seepage.

An expert from the GSI, Inder Singh, states that the spoon-shaped failure surface encircling the hillock has its origin, probably, in the tension created by a seasonal channel of the Ghaggar river originating behind the hillock, and where a subsidence of two metres was observed.

``Long spells of rain in the failure surface, made up of gravelly sandstone, soft sandrock and clay shales, may reactivate the movement along the surface again. However, the circular failure, primarily due to seepage of water, is localised and is, in no way, related to seismic activity in the Himalayas,'' adds Pradeep Singh of the GSI.

While PUgeologists uphold the argument of seepage of water, they do not rule out seismic activity to be the cause of the crack.

``We have noticed three kinds of faults — longitudinal, oblique and transverse — after combing the entire area. The displacement of land, evident from the butt in the fields, is approximately 20 cm from one crest to the other, taking a southward direction. It has raised the level of the land, varying between 10 cm and 45 cm in the fields. Also, about 20 metres of land at the top of the hill has subsided where two faults appear by as much as seven metres,'' Dr Naval Kishore contends.

Terming the mass movement of landslides on the slopes and rock-falls on the cliff face as a combination of geological and geomorphic features, Prof Ravindra Kumar says that it took place between the two winter rains, namely the end of December, 2000, and the third week of February, 2001.

Professor Gupta adds that careful scrutiny of the affected area shows evidence of friction between rocks due to faulting. This has resulted in sliken sides, a subject likely to be discussed by geologists at a field meet that will be organised shortly by the Indian Geologists Association.

Meanwhile, experts from the Wadia Institute of Himalayan Geology, Dehra Dun, and a Russian geologist, have already visited the spot and carried out research work. ``We are here because one rain will fill up the cracks on the surface of the earth. It was essentially a race against time,'' says Dr Strom from Russia.

Whatever the reason for these faults and fissures, geologists from the GSI as well as those from PU agree on one point — a thorough study of the affected area and the adjoining areas is a must before the land is handed over to the societies concerned. This, they admit, is a marathon exercise, likely to go well into the next year. Till then, HUDA will have no choice but to cool its heels as it goes about its work.

Confusion over property deals

During the initial phase of uncertainty over the status of the affected land and that of the adjoining areas in the Panchkula extension, the investors had a field day cashing in on the fears of the public about property-related matters.

While there were no distress sales as was expected by dealers, the crack cast an apprehension in the minds of not only those with property in nearby sectors, it led to confusion over the purchase of land in that area as well.

Though Panchkula is stated to be safe, experts opine that no habitation should be allowed to come up along the Shivalik foothills since tectonic activity is limited only to this area.

``If such an event reoccurs, it will bring even a single-storeyed house crumbling down. The construction of housing societies in the vulnerable area could be a disaster since collapse is imminent,'' claims Prof LNGupta of the CASG, PU.

However, an interesting aspect to this fact is that only the houses lying on the crack, which can extend further the next time it appears, will be devastated.

``Nothing will happen to those in the vicinity or even those adjoining the affected house. There is no way to predict when an event like this will happen again and there can be no guarantees for the direction it takes,'' explains GCBhambry of the GSI.

Dispelling fears of the public, the Chairman of the Department of Geology, Dr Ramesh K Kakkar, says: ``It is a local feature produced as a result of the fluctuating content of moisture. There is no need to panic but a detailed investigation is a must.''

The fracture could as well extend into the field next time such activity occurs. This, experts claim, though is not likely till the next decade or so since it takes time for tensions to build up in the earth's crust and pressure to be released, manifesting itself by way of fissures and cracks on the surface.

Pictures show geologists examining the fissures and cracks in the Ghaggar near the Nada choe — Photos by Manoj Mahajan