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A tepui //, or tepuy (Spanish: [teˈpui]), is a table-top mountain or mesa found in the Guiana Highlands of 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. Some of the most outstanding tepuis are Neblina, Autana, Auyantepui and Mount Roraima. They are typically composed of sheer blocks of Precambrian quartz arenite sandstone that rise abruptly from the jungle, giving rise to spectacular natural scenery. 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. Throughout the course of the history of Earth, the plateau was eroded, and 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 1,000 meters. On top of the mountains grow various types of forests with a wide variety of orchid, bromeliad, and carnivorous plant species.
Because of their great age, some tepuis exhibit surface features and subsurface caves typical of karst topography, formed in more water-soluble rocks such as limestone. Caves here include the 671m deep Abismo Guy Collet, the deepest quartzite cave in the world. Some of the mesas are pocked with giant sinkholes up to 300 metres in diameter and with sheer walls up to 300 metres deep. These sinkholes are formed when the roofs of tunnels carved by underground rivers collapse.
The plateau of the tepuis is 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 animal 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. 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 got 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 which have yet to be described. A few of these mountains are cloaked by thick clouds almost the whole year round. Their surfaces could previously only be photographed by helicopter radar equipment.
A few of the most notable of the 60 tepuis:
Much of the story of Pixar--Disney 2009 film Up takes place among the tepuis. The film also includes depictions of the numerous rock formations and an Angel Falls-like waterfall called "Paradise Falls".
In his 2014 novel "The 6th Extinction," James Rollins discusses the theoretical existence of endemic flora and fauna atop a tepui.
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