Тепуи: Затерянные миры Южной Америки

Table top mountain or mesa in the Guiana Highlands of South America

A tepui '/t//ɛ//p//w//i/, or tepuy (teˈpuj), is a table top mountain or mesa found in South America, especially in Venezuela and western Guyana. The word tepui means "house of the gods" in the native tongue of the Pemon, the indigenous people who inhabit the Gran Sabana. Tepuis tend to be found as isolated entities rather than in connected ranges, which makes them the host of a unique array of endemic plant and animal species. Notable tepuis include Auyantepui, Autana, Neblina, and Mount Roraima. They are typically composed of sheer blocks of Precambrian quartz arenite sandstone that rise abruptly from the jungle. Auyantepui is the source of Angel Falls, the world's tallest waterfall.

These table top mountains are the remains of a large sandstone plateau that once covered the granite basement complex between the north border of the Amazon Basin and the Orinoco, between the Atlantic coast and the Rio Negro. This area is part of the remnants of the supercontinent Gondwana. Throughout the course of the history of Earth, the plateau began to erode and fragment about 300 million years ago, and about 70 million years ago the tepuis were formed from the remaining monadnocks. There are 115 such mesas in the Gran Sabana in the south east of Venezuela on the border with Guyana and Brazil, where the highest concentration of tepuis is found. The precipitous mountains tower over the surrounding area by up to
Tepuis range in elevation from The total surface area of all 115 tepuis is approximately
Because of their great age, some tepuis exhibit surface features and caves typical of karst topography, formed in more water soluble rocks such as limestone. Caves here include the Abismo Guy Collet, the deepest quartzite cave in the world. Some of the mesas are pocked with giant sinkholes up to in diameter and with sheer walls up to deep. These sinkholes are formed when the roofs of tunnels carved by underground rivers collapse.

The plateaus of the tepuis are completely isolated from the ground forest, making them ecological islands. The altitude causes them to have a different climate from the ground forest. The top presents cool temperatures with frequent rainfall, while the bases of the mountains have a tropical, warm and humid climate. The isolation has led to the presence of endemic flora and fauna through evolution over millennia of a different world of animals and plants, cut off from the rest of the world by the imposing rock walls. Some tepui sinkholes contain species that have evolved in these "islands within islands" that are unique to that sinkhole. The tepuis are often referred to as the Galápagos Islands of the mainland, having a large number of unique plants and animals not found anywhere else in the world. The floors of the mesas are poor in nutrients, which has led to a rich variety of carnivorous plants, such as Drosera and most species of Heliamphora, as well as a wide variety of orchids and bromeliads. The weathered, craggy nature of the rocky ground means no layers of humus are formed. It has been hypothesized that endemics on tepuis represent relict fauna and flora that underwent vicariant speciation when the plateau became fragmented over geological time. However, recent studies suggest that tepuis are not as isolated as originally believed. For example, an endemic group of treefrogs, Tepuihyla, have diverged after the tepuis were formed; that is, speciation followed colonization from the lowlands. The tepuis, also known as 'islands above the rainforest', are a challenge for researchers, as they are home to a high number of new species that have yet to be described. A few of these mountains are cloaked by thick clouds for nearly the entire year. Their surfaces could previously only be photographed by helicopter radar equipment. Many tepuis are in the Canaima National Park in Venezuela, which has been classified as a World Heritage Site by UNESCO.