J'khand braved oldest tsunami

Published on Mar 29, 2006 03:28 AM IST

Scientists have found evidence that the oldest earthquake followed by tsunami, traceable in the earth?s history, took place more than 1,600 million years ago in what is now Jharkhand.

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None | ByPress Trust of India, New Delhi

Scientists have found evidence that the oldest earthquake followed by tsunami, traceable in the earth’s history, took place more than 1,600 million years ago in what is now Jharkhand. An international team of scientists from India, Japan and Poland has reported the discovery in a paper to appear in the forthcoming issue of the journal Sedimentary Geology.

This occurred long before the massive southern land mass called Gondwana land split up and the piece that now forms peninsular India floated north and crashed in the Asian land mass. Scientists analysed sedimentary rocks deposited in ‘Chaibasa Formation’ in eastern India. “The layers show deformations that have never been described before,” said Rajat Mazumder, lead author and currently a Humboldt Fellow at Munich University.

Mazumder and co-workers show that earthquakes caused the deformations “while the sediments were still being deposited and before their consolidation”. The layers containing these deformation structures are termed “seismites” and the scientists could trace the deformed horizons up to a kilometre depth.

Considering their occurrence in sediments deposited between 1,600 and 2,100 million years ago, “they are among the earliest records of earthquakes known in the Earth’s history,” the scientists reported.

According to the scientists a tsunami generated by an earthquake most likely detached a weakly consolidated silt/mud block and lifted and transported it away leaving behind a hole that gradually got filled by laminated sediment observed by them.

Though “deformation structures” in sedimentary rocks have been observed before, the authors say that in their opinion, those found in eastern India “represent the oldest unambiguous seismites”.

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