Daily RC Article 301

The Evolution of Geological Thought: From Burnet's Theories to Modern Plate Tectonics

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Mountains have long posed intellectual difficulties for those who have pondered their meaning and origins. Following a trip to the Alps in 1671, the English theologian and natural philosopher Thomas Burnet described the montane landscape with revulsion, remarking that its ‘vast undigested heaps of stone’ defy any ‘tolerable account of how that confusion came in nature’. Seeking to understand why such atrocities would even be part of Creation, he noted with scholarly astuteness that mountains are absent from the first chapter of Genesis, and thus not original features on Earth, though they had apparently come into being in time for Noah and crew to wash up on the slopes of Mount Ararat. In his treatise Telluris Theoria Sacra (1681), Burnet suggested that the primordial Earth had been a smooth ‘mundane egg’ that cracked and released the deluge that Noah had to survive. Mountains were the resulting scars on the face of the Earth, their stern presence a reminder of, and punishment for, Man’s iniquity.

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Burnet’s ideas are easy to ridicule, and were treated with particular scorn by Charles Lyell, one of the 19th century’s founding figures in geology. But as Stephen Jay Gould argued in Time’s Arrow, Time’s Cycle (1987), Burnet’s approach was rational, in that he was attempting to integrate sacred and secular knowledge into an internally consistent narrative. In fact, Burnet was correct on two counts: mountains are not primordial features; and mountain-building does involve disrupting the Earth’s outer ‘shell’ or crust. My own field, known as ‘structural geology’, concerns itself with the deformation of the planet’s crust, though of course we have long since abandoned notions of a primeval egg. We map active fault zones that generate earthquakes and ancient ones that host ore minerals or act as traps for petroleum. We help with the safe siting of large infrastructure projects such as tunnels, bridges and dams. And we document the growth of mountains.

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Geologists did not have a clear understanding of how mountains came to be there even when the first test rockets for the Apollo programme were being launched. Geodynamics had been stuck with speculative theories formulated in the 19th century when – in 1963 – the scientific paper that sparked the modern plate-tectonics revolution – an understated three-page article in Nature positing the phenomenon of sea-floor spreading – was published. But it is fascinating to listen in on the conversations among geologists who studied mountains in the century before plate tectonics. Many field-based geologists did excellent observational science that remains useful today, even though they laboured under a limiting interpretive paradigm. In contrast, some of the most prominent geologists of the time, less concerned with the messy ground truth of rocks than with staking a claim to a grand unifying theory, contributed to an elaborate fiction about the genesis of mountains that is almost as risible as Burnet’s erupting egg. Their ardent adherence to such theory exposes a basic tension in the study of the Earth: whether it can be understood like the cosmos, subject to timeless laws, or more like a language, evolving and idiosyncratic.