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The hidden secrets of the Tepuis

In the caves hidden under the Tepuis of South America, the geologist Francesco Sauro has discovered clues to the evolution of life on Earth.

By Eva Van Den Berg
Published in August 2020Time to read: 3min 45s

The Italian speleologist Francesco Sauro has a doctorate in geology from the University of Bologna and won a Rolex Award for Enterprise in 2014 for his research. He is fascinated by the remote, isolated world underlying these extremely steep table-top mountains called ‘tepuis’, impressive geological formations typical of the Guyana Highlands in north-eastern South America. Sauro has always loved the world of caves, which he says conceal an entire continent under the earth’s surface that is still largely unexplored. From a young age he started exploring the karst caves nearest to his home in the Italian Alps and the Dolomites. He soon set his sights further away, and when in 2009 he first visited the tepuis of the Orinoco and Amazon basins, he was particularly captivated by this wilderness. He was not the first person to have fallen under their spell. In 1912, Arthur Conan Doyle chose the magnificent scenery of the Roraima tepui as the setting for his novel The Lost World, the story of an expedition to a distant territory inhabited by indigenous peoples, primitive hominids and pterosaurs. Enthralled by the imposing scenery before his eyes, Sauro wondered what secrets might be awaiting discovery below the surface. It was then that he vowed to find out for himself.

The Italian geologist and speleologist Francesco Sauro received a Rolex Award for Enterprise in 2014. This article has been prepared with the support of Rolex, which collaborates with National Geographic to cast light, through science, exploration and dissemination, on the challenges facing the systems most crucial to sustaining life on Earth.

“Scientists consider these mountains as islands in time, separated from the surrounding lowlands for tens of millions of years”, he explains. Rising up with their sheer walls between 1,000 and 2,900 metres in height, they take on the appearance of stone fortresses or giant natural laboratories in which, thanks to their difficulty of access, species have evolved in total isolation. This is true not only for those that inhabit their summits, but also for the fauna that inhabit the interiors of their caves, into which Sauro and his team descended to discover dark, unknown spaces and to set foot in places that no human being had ever visited before.

There is a universe of silence in this lost world. It has been absolute. Your footsteps are the first sound, perhaps for millions of years.

Tepuis are largely made up of quartzite, a metamorphic rock with a high quartz content that is highly insoluble—the complete opposite of the rock found in karst systems, which becomes so malleable under the action of water. How then can it be explained that these magnificent cave systems have formed in rocks of such extreme hardness? The key factor here is time, explains Francesco Sauro. “The geological history of the tepuis is extraordinarily long, and the formation of these rock structures goes back some 1.7 billion years. Much later, some 150 million years ago, the terrain rose up due to the significant movements of the tectonic plaques caused by the separation of the Pangaea supercontinent and the opening up of the Atlantic Ocean. Water took tens or hundreds of millions of years to carve the strangest shapes in the surfaces of the tepuis. However, nobody knew what had happened in the interiors of these mountains during such a long period of time.”

Inside the Imawarí Yeuta cave, Francesco Sauro observes an extraordinary opaline formation created by an ancestral bacterial community, a discovery totally new to science. This cave is located under Auyantepui, the largest tepui in Venezuela, which features enormous waterfalls including the Churûn Falls and the Angel Falls, the highest waterfall in the world.

In 2010, Sauro and his team of speleologists from the Italian association of geographical exploration La Venta explored the Auyantepui, the famous tepui in Venezuela whose summit features the Angel Falls, the world’s highest waterfall, measuring a total of 979 metres. They were looking for evidence of cave systems in the region through satellite images and identified an area in which depressions, high cliffs and steep rock formations could be seen. “It was clear evidence that there must be an empty space under the mountain”, the geologist recalls. “We made several attempts to gain access to this zone, both on foot and by helicopter, but it was very difficult. Covered by clouds most of the year, this giant plateau is buffeted by strong winds and frequent rainfall.” They finally succeeded in 2013 and, relying on all their skills as expert cave explorers, discovered the long sought-after cave, an incredible site with pink quartz walls, red underground watercourses brimming with organic acids, and the most extraordinary speleological features (stalactites and stalagmites) carved out of the silica by colonies of micro-organisms working together to form this series of bacterial skyscrapers. They gave the site the name Imawarí Yeuta, meaning ‘the House of the Gods’ in the language of the Pemon people. Although there were legends referring to its existence, the Pemon people had never succeeded in reaching this fantastic cavity.

With over 20 kilometres of tunnels, this enormous cave was explored using special protocols so as not to pollute the environment, and involving the indigenous community in all their discoveries.

Unlike the events described in Conan Doyle’s novel, Sauro did not discover any dinosaurs under the tepui, but did succeed in identifying mineral formations that were totally new to science, such as an aluminium sulphate that they named ‘rossiantonite’, and some fascinating colonies of unknown bacteria, capable of extracting energy from sulphates of atmospheric origin that they capture through porous structures made of silica. This vast territory is full of opportunities to conduct research into the evolution of life on Earth in its most primitive phases. Any organism found in these ecosystems – including spiders, insects and even the skeleton of a wild cat dating back some 5,500 years – has evolved entirely free of outside influence.

Sauro’s team has now completed 33 expeditions to caves in different locations all over the world, and 10 to the tepuis of Venezuela and Brazil thanks to the support of Rolex and its Awards for Enterprise, accolades that since 1976 have encouraged projects to protect our planet and to improve conditions of life in fields as diverse as health, technology, and the exploration and preservation of our cultural and environmental heritage. Sauro now intends to extend his area of study to other quartzite caves in South America.

In the depths of the table rock formation known as Auyantepui, which in the Pemon language means “"mountain of the devil”, Loredana Bessone, a member of the team of Italian speleologists led by Francesco Sauro, admires the impressive speleological features that proliferate in this enormous cavity. Situated in Venezuela’s Canaima National Park, no human being had ever before set foot inside it.

The study of these isolated realms is also extremely useful for training astronauts to live in a non-terrestrial environment. In collaboration with the European Space Agency (ESA), Sauro coordinates space training programmes inside various caves, in which some thirty astronauts have participated to date. It takes longer to reach these hidden underground destinations, pervaded by an atmosphere of total isolation and darkness, than it does to travel to the International Space Station, which requires a journey of between six and eight hours. Collaboration between participants is a key factor, as it is in all space missions. “During the next expeditions to the Moon or to Mars astronauts will need to live for many months away from our planet, and these caves offer an ideal safe environment to prepare for this experience”, adds Sauro, who also provides advice to the various space agencies in their search for regions on the Moon or on Mars that could host caves suitable for establishing extra-terrestrial colonies.

“Caves bear witness to geographical history,” concludes Sauro. “In caves everything is much better preserved than on the surface. They are archives providing keys to the passage of time, the evolution of the landscape and the evolution of life itself.” It is clear that there is much more to our planet than what we are able to see of it from the surface. In the same way that the oceans have, caves have also opened up a new dimension for us that Sauro and other speleologists are helping us to understand.

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