When British explorer George Leigh Mallory was asked, “Why climb Mount Everest?” he succinctly replied, “Because it is there.” In 1924 he attempted the ascent for the second time. During the final attack the expedition’s geologist, Noel Odell, looked up from 25,000 feet. Through a break in the clouds he could make out the dim silhouettes of Mallory and Andrew Irvine facing a steep incline near the top. But the clouds quickly closed that window; Mallory and Irvine were never seen again .
This fleeting image of Mallory wasn’t the only memorable thing Odell saw on the 1924 expedition. Up there, he also discovered the fossils of shelled sea creatures that had been buried in a shallow sea 250 million years ago. How is it possible that the bottom of a sea could become the roof of the world?
Everest is not the only place in the Himalayas where remains of archaic marine inhabitants can be found. In the villages of the Kali Gandaki River Gorge, where farmers gather fruit and grain in the shadow of the more than 8,100-meter Dhaulagiri, Nepalese children sell salagramas , which are nothing more than ammonites, to visitors on the streets .
That same year appeared the English translation of a short monograph by a Berlin meteorologist, the son of a preacher, named Alfred Wegener . It was the third edition of an idea he published in 1915 and sparked heated discussions during the second quarter of the 20th century. His proposal was simple and explained the formation of mountain ranges and something that both the philosopher Francis Bacon in 1620 and any schoolboy who has looked at a world map realizes: South America and Africa seem to be made for each other. In short, that the continents have not always been there but that they move through the earth’s crust like drifting icebergs.
marry continents
A hundred years after Bacon, the great explorer and naturalist Alexander von Humboldt explained in some detail how the New and Old Worlds had become separated due to the effects of the waters that fell during the universal deluge, which, circulating from north to south, had excavated The Atlantic ocean. But it was not until 1858 when Antonio Snider-Pellegrini, an American living in Paris, first reconstructed the supercontinent that existed before the opening of the Atlantic. Thus Snider explained the striking similarity between fossils found in coal seams in Europe and North America. The explanation was that a catastrophic event, perhaps the universal flood, had caused this separation.
The great defender and publicist of this world view, although less catastrophic, was Wegener. He defended that all the emerged land had been united in a «supercontinent», Pangea, which had fragmented and whose dispersion gave rise to the current arrangement of the continents. His contemporaries did not believe him. The poor man was called everything. It was not for less; he was demolishing one of the most sacrosanct dogmas of geology, the product of years and years of careful research. One of the participants in the 1928 symposium sponsored by the American Association of Petroleum Geologists said: “If we accept Wegener’s hypothesis we can throw away all the knowledge we have been teaching for the last 70 years and start again.” Years later, when Wegener died among the ice of Greenland in 1930, it was said that there was no need to mention Wegener’s absurd idea to students so as not to mislead them. For 25 years the only proponents of the ‘continental drift’ theory were three great geologists: Arthur Holmes, Sir Edward Bailey and Wegener’s disciple Alexander Du Toit. Today, it would be totally impossible for any geophysicist or geologist to obtain a teaching position if he did not believe in plate tectonics, the natural daughter of Wegener’s continental drift.
The birth of a new geology
In 1967 Dan McKenzie and RL Parker published an article in the prestigious Nature that has become a classic. In a valiant effort at synthesis, they showed that geophysical features could be explained by the existence of seismically quiet, mobile, rigid plates that interact with each other only at their edges. These two geologists picked up the brilliant suggestion of Harry Hess, from Princeton University, when in 1960 he presented his work on the expansion of the ocean floor: they are not static, as everyone thought, but mobile. The Atlantic, for example, increases in width by 2.5 centimeters per year – or 25 kilometers in a million years – and new soil forms on the ridge that runs north to south through the center of the ocean. In this way, the oceanic crust is older the further away it is from the ridge that generated it; a crust that is destroyed in the so-called subduction zones of the oceanic trenches, where it collides and sinks below the adjoining plate. Thus, today we know that in no ocean in the world are there sediments older than the Jurassic , just over 200 million years ago.
Between 1967 and 1969 three young geophysicists, the Americans Jason Morgan, Dan McKenzie, and the Frenchman Xavier Le Pichon, formulated what would soon be known as the theory of plate tectonics , a work that sparked an explosion of new geological research that confirmed their predictions. : modern geology was born.
In essence we were told that the Earth’s crust is like a soccer ball . It is not a single surface but is divided into plates. But unlike what happens in the ball, these plates are of different dimensions and are floating in a sea of liquid magma, the mantle, on which they move and in the same way that happens with ships, the plates are more or less sunk depending on the weight.
References:
O’Hara, K. D.(2013) A Brief History of Geology, Cambridge University Press
