Mount Roraima

Mount Roraima (Monte Roraima; Tepuy Roraima; Cerro Roraima; Monte Roraima) is the highest of the Pacaraima chain of tepuis (table-top mountain) or plateaux in South America. It is located at the junction of Brazil, Guyana and Venezuela. A characteristic large flat-topped mountain surrounded by cliffs 400 – high. The highest point of Mount Roraima is located on the southern edge of the cliff at an elevation of 2,810 m in Venezuela, and another protrusion at an elevation of 2,772 m at the junction of the three countries in the north of the plateau is the highest point in Guyana. The name Mount Roraima came from the native Pemon people. Roroi in the Pemon language means "blue-green", and ma means "great".

Leaching caused by intense rainfall has shaped the peculiar topography of the summit, and the geographical isolation of Mount Roraima has made it home to much endemic flora and fauna. Western exploration of Mount Roraima did not begin until the 19th century, when it was first climbed by a British expedition in 1884. Yet despite subsequent expeditions, its flora and geology remain largely unknown. The privileged setting and relatively easy access and climbing conditions on the south side of the cliffs make Mount Roraima a popular destination for hikers.

Geography
Mount Roraima is located in the northern part of South America, the Pacarema Mountains in the eastern part of the Guyana Plateau, Brazil in the east accounting for 5% of its area, Guyana in the north accounting for 10%, and Venezuela in the south and west accounting for 85%. Access to Mount Roraima from the Venezuelan side is close to the road and relatively easy; however, for both Brazil and Guyana the area is completely isolated and can only be reached by a few days of forest hikes or small local airstrip.

Mount Roraima is a flat-topped mountain, typical of the Guyana Shield, with an elevation of about 1,200 m in the southeast and only about 600 m in the northwest. The south, southeast, east, northeast and northwest faces are all formed by straight cliffs up to about 1,000 m high. At the southern end of the mountain, part of the cliff has collapsed, forming a natural boulder. The base of the cliff is surrounded by steep slopes to the south and east, and the north and west sides form river valleys leading to the summit.

The top of Mount Roraima has a length of more than 10 km, a maximum width of 5 km, an area of about 33 –, an elevation of more than 2,200 m, and an average elevation of 2,600 –. The plateau is a pseudo-karst surface etched by heavy rainfall. The highest point is 2,810 m above sea level, located at the southern end of the plateau and the highest point in the state of Bolívar,  8.25 km north of the summit is another high point with an elevation of 2,772 m, which is the highest point in Guyana. In the northern part of the plateau is the landmark of the border between Brazil, Venezuela and Guyana, with an elevation of 2,734 m.

Due to its height and proximity to the equator, Mount Roraima has a constant average annual temperature between 20 – and annual rainfall of more than 1,500 mm, with 1,800 – in parts of the rainy season from April to November. The climatic conditions at the top of the mountain differ significantly from its base, the high cloudiness in the region is associated with the prevailing northeasterly and southeasterly winds, and the relative humidity of the air remains between 75% and 85%.

Geology
Mount Roraima is composed of Proterozoic age sandstone formed about 1.7 to 2 billion years ago,   and hence amongst the oldest rocks on Earth. It contains a large amount of quartz deposits, 98% are silica particles, forming white or pink crystals several centimeters long. These rocks sit on a granite and gneiss base and were originally covered by layers of Mesozoic clay, conglomerate, and diorite, but have been exposed by erosion and by orogeny over the past 180 million years, eroded by precipitation to form strange shapes. The soil of the sandstone matrix is highly acidic, poor in nutrients, and very fine. Intense rainfall prevents the fixation of nutrients and particles, thereby preventing the formation of hilltop vegetation and soil.

The numerous caves and rifts in the interior of the plateau make Mount Roraima exhibit a pseudo-karst structure, and these caves form a network over 15 km long, with a total height difference of 73.21 m. It contains the largest quartz cave in the world, discovered by the Oxford University Cave Club and the Venezualan Speleological Society. These caves are formed by the infiltration of surface water, so the water level inside them depends largely on the precipitation on the surface of the plateau: prolonged drought can dry up waterways, and dry caves can also become underground rivers. The water that poured into it rushed into the crevices of the rock and flowed out in the form of waterfalls on the mountainside, creating many streams at the foot of the mountain.

Ecology
Due to the late exploration of this part of South America and the discovery of new species every year, the flora and fauna here are largely unknown. The currently identified species are strongly endemic, especially the fauna, which also puts them at a high risk of extinction. The bottom of the cliff at the foot of the mountain is an evergreen rainforest composed of trees 25 – high, and some can reach 60 m. Vegetation is dominated by Arecaceae and Astragalus. The soils on the cliffs are more sandy, the climate is cooler, and the vegetation consists of bromeliads very similar to the Andes. The vegetation on the plateau is still largely unknown and consists mainly of bare rocks, forests of trees and epiphytes, and wet and dry savannas in the form of swamps. It is marked by numerous endemic species, especially carnivorous plants that capture insects and find them there in sandstone and leaching soils without the nitrates necessary for their development. There are fewer species in the vicinity of streams and ravines, and the trees are 8 – tall and have hard leaves that can adapt to harsh environmental conditions. The exposed rocks are occupied by lichens, algae and cyanobacteria.

The fauna at the foot of the mountain are composed of a variety of mammals, and this huge diversity is particularly prominent in the Amazon rainforest, such as sloths, anteaters, tapirs, armadillos, capybaras, opossums, agouti, weasels, raccoons, deer, cougars, and primates such as howler monkeys and capuchins. There are hundreds of species of birds, the most common of which include falcons, parrots, and owls. Some hummingbirds are endemic to the region. Due to low mobility relative to other species, reptiles and amphibians show large differences between individuals found at the bottom and top of Mount Roraima. While species inhabiting forests at the foot of the plateau are common, such as green iguanas, pit vipers, coral snakes and pythons, those found at the top are even rarer. Cave fauna consists of many species of bats, grasshoppers, spiders and centipedes, but this fragile subterranean ecosystem is being disturbed by surface hikers, organic matter produced by tourists, and explorers over the years. Pollutants such as fuel are washed into the ground by rainwater, which leads to the proliferation of microorganisms and causes ecological imbalance.

Exploration
European discovery was in 1595, during a Spanish and British race to colonize this part of South America. The English poet, army officer and explorer Walter Raleigh described it as an immeasurable "crystal mountain" gushing countless waterfalls. The first expedition to Mount Roraima took place in 1838, when German scientist and explorer Robert Hermann Schomburgk observed it during a Royal Geographical Society-funded expedition to explore British Guiana (1835–1839). In 1840, the British government commissioned him to establish the boundaries between British Guiana and Venezuela. When he returned to the area in 1844 to study the local flora, he reported that the peak seemed inaccessible due to its towering cliffs. In 1864, German naturalist and botanist Carl Ferdinand Appun and British geologist Charles Barrington Brown arrived at the southeastern tip of Mount Roraima for observation and proposed to go up the mountain by hot air balloon.

Although its vertical cliffs make access very difficult, Mount Roraima was the first large mesa to be climbed in the Guyana Plateau. Henry Whiteley, who studied the birds of the area, observed that the summit could be reached from the south with the help of ropes and ladders. Everard im Thurn and Harry Perkins led an expedition sponsored by the Royal Geographical Society that culminated on December 18, 1884, when the team found even a local Aboriginal Pemon. Passages unknown to man, they indicate that the top of the cliff has been unknown since the dawn of man. Soon, many expeditions made up of botanists, zoologists and geologists made multiple expeditions to Mount Roraima to study the mostly unknown flora and fauna and special geological conditions of the area.

Climbing
Mount Roraima and Mount Aoyan are the only flat-topped mountains in the Canaima National Park that can be climbed by hikers, with a monthly quota of 200 people. Its ascent takes three to five days in total, the summit route is on a natural slope on the southwestern cliffs of Mount Roraima,  it does not require any special equipment or training, so it is chosen by almost all hikers,  the only difficulty is that some streams and small waterfalls may become difficult to pass under heavy rain. However, the length of the trail requires climbers to spend one night at the base camp at the foot of the cliff at an elevation of about 2,000 meters, and another night at the summit, taking several days to explore the plateau and two days to descend. The best time to climb Mount Roraima is in the dry season, however, when the sun is very strong and the temperature is high, it can make the road to the mountain difficult.