Venezuela's "Islands In The Sky", Explained.

This is Angel Falls, and it is the tallest waterfall on Earth. It drops a staggering 979 meters in a single, uninterrupted plunge off the edge of a mountain in southern Venezuela. The water falls so far that much of it turns into a mist even before it reaches the ground. But none of this is probably news to you, because most people have heard of Angel Falls. But most people don't know what mountain it falls from, or why that mountain exists, or what's on top of it, or what the people who have inhabited this landscape for thousands of years believe about it. Today, that is about to change. This mountain, or rather plateau, is called the Allianz Tepui. It is one of roughly 115 formations scattered across the Guiana Highlands of Venezuela, Guyana, and Brazil. And in my opinion, this is one of the most fascinating parts of the planet. These formations are known as the Tepui. They are flat-topped mountains rising up to a thousand meters above the landscape. And each one of these almost acts like an island in the sky. Each one carrying on its summit an ecosystem that has been isolated for a long time. And all of this makes this region, the Guiana Highlands, one of the great geographical stories on the planet. But what are the Tepui and how were they formed? Well, the Tepui are the remnants of what geologists called the Guiana Shield, one of the oldest exposed rock formations on the surface of this planet. The ancient layers of rock that makes up the Tepui plateaus was laid down as sediment on the floor of an ancient sea roughly 1.7 billion years ago. To put that into perspective, it is estimated that complex animal life didn't begin until 530 million years ago. The rock on the Tepui was already ancient before the first fish appeared in the ocean. And for the vast majority of that time, these formations were not mountains at all. They were part of a vast, flat plateau. So what happened between that time to the present day? How did the Tepui go from one massive plateau to hundreds of individual plateaus? What happened was differential erosion. Keep in mind that the rock of the Tepui is extraordinarily hard, primarily made up of quartzite. The softer rock around it eroded away. Rivers, rainfall, and time wore down everything that was less resistant. And slowly, over an almost incomprehensible span of time, the plateau was dismembered, worn away on all sides, leaving behind the most resistant sections as isolated, flat-topped mountains rising above the eroded lowlands. So the Tepui you see here are what's left. They are not mountains that were built up. They are a plateau that was carved away. They are just what remain. And as the lowlands eroded away from them, the summits became isolated. Not immediately, but slowly. The cliff faces of the tallest Tepui are sheer, vertical rock walls hundreds of meters tall. They're smooth and overhanging in places, offering almost no route for organisms to travel between the summit and the jungle below. The summits became, in biological terms, islands. And on islands, whether surrounded by water or air in this case, evolution does its most creative work. Now, the summits of the Tepui have been isolated for millions of years, long enough for evolution to produce species found nowhere else on Earth. The Tepui region has one of the highest rates of plant endemism anywhere in the world, meaning a remarkably high proportion of its species exist on these summits and nowhere else. Some individual Tepui have endemic species found on that single formation and no other. Now, an important distinction we need to make is that the soils on the Tepui summits are among the most nutrient-poor on the planet. The ancient rock weathers into sand that retains almost no minerals. Water pools in shallow depressions, which are acidic and dark. Normal tropical vegetation cannot survive here. What has evolved instead is a suite of highly specialized plants. Most are slow-growing and compact, many of which have actually developed to be carnivorous due to nutrient scarcity. Sundews, pitcher plants, and bladderworts are organisms that catch and digest insects to obtain the nitrogen and phosphorus that soil cannot provide here. If you are ever so lucky to walk across a Tepui summit, which by the way is definitely on my bucket list, you might think you're walking on another planet. The vegetation is low and strange. The rock is black with cyanobacteria and stained rust red with iron. There's pools of dark water that sit in shallow depressions. The clouds move here through eye level, reducing visibility to mere meters. And as these clouds part, they reveal a view of hundreds of kilometers of jungle spread below like a green ocean. It truly is one of the most beautiful landscapes on earth. Now, this region is concentrated in what's known as the Guiana Highlands, and this is one of the most sparsely populated and isolated regions in South America. The infrastructure here is minimal at best, and the terrain, well, of course, it's formidable. Venezuela contains the greatest concentration and the most dramatic individual Tepui. The state of Bolivar in southern Venezuela is home to the Canaima National Park, a UNESCO World Heritage Site covering nearly 30,000 square kilometers. Within Canaima sit some of the most famous Tepui, from which Angel Falls descends, Mount Roraima, the highest and arguably the most iconic, and the cluster formation of the Grand Sabana, where dozens of Tepui rise from a high altitude grassland that itself sits above 1,000 meters. It really feels like a magical landscape and a place that inspired many stories, such as Sir Arthur Conan Doyle's 1912 classic novel, The Lost World. But of all the Tepui, Mount Roraima is the one that most fired western imagination. It sits at the tri-point of where Venezuela, Guiana, and Brazil meet. It rises approximately 2,810 meters above sea level, with cliff faces on each side dropping 400 meters. Mount Roraima is perhaps the Tepui most closely associated with Conan Doyle's The Lost World, the story of a plateau in South America where prehistoric creatures had survived, isolated from evolutionary changes by their cliffs. Conan Doyle had never visited Roraima, but he had read accounts of the first European ascents in 1884. Their descriptions of the summit, the bizarre plants and strange rock formations, the sense of absolute separation from the world below, were enough to inspire the author. The novel was fiction, but the biological realities of life on Roraima's summit might be just as strange. Because the summit holds species found nowhere else on earth, including the strange Roraima bush toad. A small, dark amphibian that has lived on this summit for so long, isolated from its nearest relatives below, that it has become its own distinct species. And interestingly, it's evolved a unique defense mechanism. When threatened by predators, the toad curls into a ball and rolls away. Then there is the Aoyan Tepui. The name literally means devil mountain in the Paman language. It is one of the largest Tepui, covering roughly 700 square kilometers on the summit plateau. It is deeply dissected by canyons and gorges, and it receives some of the highest rainfall of any Tepui. Angel Falls drops from a notch on the northern rim of the Aoyan Tepui into the Churun River Gorge below. The full height of the fall is 979 meters, of which the uninterrupted initial drop is 807 meters. For comparison, the Eiffel Tower is only 330 meters tall. The Empire State is 443 meters. Angel Falls drops more than twice the height of the Empire State Building. But why is it called Angel Falls? It's actually named after an American pilot called Jimmy Angel. He was the first Westerner to document Angel Falls. His flights in the region actually helped explore, map, and evaluate the Tepuis and the Grand Sabana region. Biologically, the Tepui can be best described as the Galapagos of the sky. The Galapagos Islands are famous for producing distinct species through isolation. The Tepui have also been doing the same thing. But here, the isolation is not oceanic, but altitude. The cliffs replace the sea, but the evolutionary mechanism is pretty much the same. The region of the Guiana Highlands is extremely biodiverse, and much of that diversity is concentrated in its endemism. According to recent studies of the Tepui, it is believed that this region harbors nearly 1,300 endemic species of plants alone. But have humans ever lived in this strange and unique environment? The short answer is yes. The Pamon people, an indigenous group of perhaps 30,000 to 40,000 people living across the Grand Sabana and adjacent areas of Venezuela, Guiana, and Brazil have lived in the shadow of the Tepui for at least several thousand years, and possibly much longer. Their language, their cosmology, their entire understanding of the world is structured around the mountains that dominate their landscape. For them, the Tepui are holy places, sacred guardians of the savannah. According to their beliefs, the Tepui are home to the Mawari, ancient ancestral spirits that are sometimes considered dangerous. Now the summits of most Tepui were not regularly visited by the Pamon. The difficulty of the ascent and the spiritual weight of those mountains combined to make them places of respect rather than habitation. The first ascent of a Tepui was the 1884 expedition by British explorer M. Third. But even before all of that, European awareness of the Tepui region dates back to the late 16th century, when Walter Raleigh led an expedition up the Orinoco River in search of the famous El Dorado, that mythical city of gold that Raleigh's 1595 account, the discovery of the large, rich, and beautiful empire of Guiana, described flat-topped mountains in the interior with a vividness that suggested he or his sources had seen them. But El Dorado was never found, at least not in the form the Europeans imagined. But the search for it drove European penetration of the Guiana highlands for nearly two centuries, and it brought the Tepui into Western consciousness, however distorted, long before any scientist actually set foot on a summit. From that moment, the Tepui became objects of fascination, expedition, and scientific inquiry that has continued with varying intensity ever since. But in a way, there is still so much to learn about the Tepui. Because of the 115 Tepui formations identified, many of which have still not been studied in a systematic way, many have never even been visited by biologists at all. Each new expedition to a previously unstudied summit returns with new species to science, whether that be plants, insects, or amphibians. In an era where it feels as though the entire surface of the earth has been catalogued, the Tepui represent a genuine frontier for exploration. Now there is another piece of puzzle that I haven't mentioned yet, and that is the cave systems within the Tepui. Now this is another major frontier in terms of exploration. Because erosion has carved extensive cave networks into the sandstone, some of the largest quartzite caves in the world are found here, including the famous Cueva del Fantasma, a huge cave that's only recently been found. The name stands for Cave of the Ghost in Spanish, and it's so vast that almost two helicopters can comfortably fly in and land. There's actually already been new species of poison dart frogs found in this cave. What else can be found in these caves? Are there other species of amphibians? And what microorganisms inhabit this perpetual darkness? So we started this video by talking about Angel Falls, the tallest waterfall in the world. The kind that appears on Instagram posts, on screensavers, and travel posters. But behind that waterfall is a billion year old geological history. It's located on a mountain and an ecosystem that has been evolving in isolation for a long time. And around the mountain are people who have known it, named it, and built their understanding of the world around it for thousands of years. And even inside the mountain are caves that have never been explored. The Tepui of this region really are one of the most fascinating geological and geographical stories on the planet. Over the years, biologists have studied this ecosystem. But there is a lot we still don't know. And we are still learning, still finding new species every time we visit. Hence proving that despite modern day science, there is still so much we do not know about this beautiful planet. And as always, if you like content like this and you like learning more about the planet and its cities, its landscapes, and its countries, don't forget to hit that subscribe button. There's a lot more awesome content on the way, so stay tuned. And if there's any specific topic, a place, a city, a region, a country, a landform, that you want me to cover on this channel, let me know in the comments below. I genuinely love reading the comments and the ideas that people have. And as always, I will catch you in the next one. Peace.