It’s the age-old question – how did the dinosaurs die out? What if volcanic activity was responsible for their extinction? And are we heading for another mass-extinction today? Step back 66 million years and try to uncover the answers to these questions and the big one – did volcanoes kill the dinosaurs..?
Probably yes! After dominating the land for over 100 million years, the dinosaurs suddenly disappeared 66 million years ago. Many people believe that their extinction was caused by a giant, 10km meteorite from space which landed just off the coast of what is now Mexico. Certainly we know that this happened, because the remains of the crater itself have been discovered on the shallow sea bed, along with evidence from the rocks of gigantic tsunamis. But many palaeontologists think that the extinction of the dinosaurs, along with many, many other species of all kinds of plants and animals, is not so easily explained, because there is evidence that huge volcanic activity was going on at exactly the same time. If you travel to the central region of India you will find a huge hilly area called by geologists the Deccan Traps. This is the name given to an enormous volume of rock that formed from molten volcanic lava. Like the meteorite, these rocks too dated from 66 million years ago.
The sudden loss of over half of all the plants and animals on the planet, sea, freshwater and land dwellers alike, is called a mass extinction. The fossil record shows us that mass extinctions have happened every 20-30 million years throughout the whole history of life on Earth. Indeed, the one that saw the end of the dinosaurs was not even the largest – that dubious distinction goes to what is called the end-Permian mass extinction about 200 million years ago, when over 90% of all species died out. Most of these catastrophic events have been discovered to coincide in time with massive volcanic activity. The great outpouring of noxious gases from them must have had a disastrous effect on the environment. Carbon dioxide in the atmosphere causes a large rise in temperature. As the sea grew hotter, less gas could dissolve and so many organisms were starved of oxygen. Sulphur dioxide would have combined with water vapour in the atmosphere to make sulphuric acid, which fell as acid rain killing much of the plant life on land. Meanwhile toxic metals such as mercury accumulated and poisoned large areas.
So did the dinosaurs suffer extinction because of the meteorite or the volcanoes? We do not really know yet. None of the other great mass extinctions seem to have been triggered by a meteorite impact, although there are a few hints of it in one or two cases. It may simply be coincidence that a giant impact happened at the same time as the volcanic activity 66 million years ago. This would undoubtedly have made the effect on life even worse than if only one of these disasters had struck. Or it may be that the impact itself somehow triggered the volcano in this case. Whatever the truth, it seems certain that the magnitude of volcanic outpourings at times in the past unimaginatively exceeded anything we see today, and the effect on life and its evolution can hardly be overstated.
A possible avenue for investigation
The Earth is suffering a sort of mass extinction right now, and many species are in grave danger of extinction. It is often called the “6th mass extinction”, and unlike earlier mass extinctions, it is the result of human activities. How similar do you think the causes of this 6th extinction are to the effect of volcanoes in the pre-human past?
(e.g. Rate of extinction probably higher. Similar gases causing similar effects. Toxic pollution comparable to metallic pollution.)
Dr Tom Kemp is a research fellow at Oxford, who regularly teaches palaeobiology undergraduate courses both in Oxford and Cambridge. Tom is a former curator of the University of Oxford’s Museum of Natural History and his research focuses on the fossil “mammal-like” reptiles of the Permo-Triassic, which are intermediate in grade between primitive reptiles and true mammals.