The end of the dinosaurs - the Seychelles connection !

The dinosaurs died out about 65 million years ago, presumably driven to extinction by some mega-catastrophe. The granitic part of Seychelles was formed about 65 million years ago, when a tiny piece broke off from near where Mumbai is now in India, then drifting north towards Asia after it had broken off from Africa and Madagascar.

Basalt ("ros lefwa") from Praslin and the volcanic rocks of Silhouette and Ile du Nord are around 65 million years old. Could it be just a coincidence that all this happened at around the same time - or is there a connection?

The link could be massive volcanic eruptions responsible for the thick sheets of basalt that engulfed the part of north-western India known as the Deccan traps ... yes, around 65 million years ago. One theory is that this violent volcanic activity was triggered off as India passed over the otspot - a place where hot molten rock is rising to the surface from inside the earth - that is now producing the Piton de la Fournaise volcano in Réunion. Some geologists believe this also caused the rifting that separated Seychelles from India, and produced the volcanic rocks such as the basalt that we see today as black dykes intruding into the older granite rock. But what, you may ask, is the connection with the disappearance of the dinosaurs and, indeed, that of many other animals and even plants?
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An artist’s impression of a dinosaur. Scientists are still divided over what caused the demise of the dinosaurs

This was a hot topic in more ways than one when some 14,000 scientists met in San Francisco recently for the annual meeting of the American Geophysical Union. An old debate started all over again. On one side are those who believe the dinosaurs died out as a result of a sort of "nuclear winter" caused by dust and other debris from the impact of a giant meteorite that hit Mexico - about 65 million years ago! The opposite camp is made up of those who say the dinosaurs were killed off by poisonous fumes from the volcanic eruptions in India.

Those who defended the second theory most fiercely at the San Francisco meeting were Gerta Keller of Princeton University, Vincent Courtillot from the Université de Paris and Sunil Bajpai of the Indian Institute of Technology. They say the lava erupting at the surface of the earth probably released from 10 billion to 150 billion tonnes of sulphur dioxide, which turned into toxic clouds of sulfate particles in the upper layers of the atmosphere. According to Keller, Courtillot and Bajpai, these "sulphate aerosols" poisoned the dinosaurs and many other life forms.

They point to fossilised plankton and even dinosaur eggs covered with lava found in the Deccan area, saying that this is strong evidence for their theory.

Needless to say, the defenders of the meteorite impact theory reject all this. But while more geophysical research needs to be carried out to improve our understanding of all these episodes in the Earth's history, Seychelles seems to be at the centre of many of the theories going around. In 1986 one scientist suggested that the possible impact site of the deadly meteorite could have been ... the Amirantes Basin!

by Pat Matyot

The Island Conservation Society promotes the conservation and restoration of island ecosystems.