Geology - How to Find a Dinosaur

[a TED Talk by Kenneth Lacovara]

The formula for finding a dinosaur is simple - first find rocks of the right age, those rocks must be sedimentary rocks, and layers of those rocks must be naturally exposed, then the chances of finding fossils are good. Dinosaurs lived in the Mesozoic Age - 235 to 66 million years ago - so use a geological map, first produced by William Smith, to locate areas where rocks of the right age occur in desert conditions. The fourth requirement is to get as far away from other palaeontologists as possible.

At the bottom of Patagonia, all these conditions were met, and first an isolated dinosaur femur, 2 metres long, was discovered, then a whole skeleton of a new giant plant-eater named Dreadnaughtus schrani. It was 85 feet from snout to tail, stood 2.5 storeys at the shoulder and would have weighed 65 tons - the weight of 8-9 Tyranosaurus rex. Big plant-eaters today can be aggressive (bison kill more people than bears in Yellowstone National Park) and D. schrani would have been incredibly territorial and dangerous, whilst having nothing to fear itself - hence the name. Its long neck would have allowed it to forage a large area of vegetation without expending any energy, and its legs were wide apart to prevent it from falling over (a fatal accident for anything that heavy).

This specimen was buried, defleshed by bacteria and its bones became like the entombing rock. As more sediment accumulated, pressure from all sides weighed in like a stony glove, stabilising the bones as epochs passed uneventfully by. Meanwhile, up above, the dinosaurs were wiped out by a meteorite, mammals took over and a primate evolved into humans, spreading across the planet, one of whom would eventually stumble across the grave of this specimen. Although for an individual the chances of fossilisation are minute, over geological timespans the improbable becomes the collectively inevitable. The bones of Dreadnaughtus lay underground for 77 million years.

At its source, the Missouri river is a mere trickle but, by the time it reaches the sea, it becomes vast, even though an identical stream nearby fizzles out in a pond. There are an infinite number of possible histories, but we only get the one we find ourselves in. Studying the ancient past gives us perspective and humility. Dreadnaughtus was snuffed out in a cosmic accident over which it had no control. The fossil record tells us that our place on this planet is precarious and potentially fleeting but, unlike the dinosaurs, we do have a choice. Our species is propagating an environmental disaster of geological proportions that can rightly be called the sixth extinction but we can see it coming and do something about it. That choice is ours.

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