|Location:||South of Puerto Ayacucho, Gran Sabana, Federal Amazonas.|
|Classification:||Erosional cave, Lower Precambrian sandstones and quartzites of the Venezuelan Guiana Shield|
|Dimension:||L=395m, H=40m, A=1,150m asl.|
F. Urbani, E. Szczerban (1974):
Venezuelan caves in non-carbonate rocks: a new field in karst research,
National Speleological Society News, 32(12):233-235.
|As far as we know this information was accurate when it was published (see years in brackets), but may have changed since then.
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|1971||first explored by Charles Brewer-Carias and Robert Madden.|
|1978||Cerro Autana declared a Natural Monument.|
Cerro Autana is one of those towers or tablelands, typical for the Venezuelan rain forrest. They are so extraordinary and impressive, they gave an ideal location for Sir Arthur Conan Doyle's book The Lost World. The bigger ones are called tepui, which means flat-topped mountain. This small tepui is called cerro, which means tower or mountain. Cerro Autana has 1,400m high vertical walls above a plain of rain forest and swamp.
The tepui are generally composed of really solid quartzite, a sandstone of quartz sand in a matrix of quartz. Once there was a huge plateau of quartzite, which was cracked and fragmented by the forces of plate tectonics. This started both the underground erosional process and the formation of the tablelands.
Quartzite is extremely resistant against any sort of erosion, still it is eroded by the high temperatures and high humidity of the Amazonas rain forest. The typical form of erosion are the tepui. The sandsone is eroded at the foot of the cliff, the debris at the foot is transported away, as fast as the wall continually looses material. This process keeps the walls almost vertical. The erosion on top of the plateau is much slower, as the rocks are protected by a layer of vegetation and soil.
Sometimes the cliffs form overhangs and huge caverns. But what happened to Cerro Autana is really unique: erosion from two sides cut through an erosional cave inside the rock. This lead to a huge portal, a natural bridge, a huge through cave going through the enormous mountain. This cave passage is almost 400m long and 40m high.
Many of this erosional caves are found in the quartzite plateaus. They are said to be the oldest caves of the World, formed about 300 Million years ago, but it seems there is no real evidence so far. The caves once drained the original plateau, but now most of them became dry. Only some caves in the bigger tepuis still have a cave river draining the remaining plateau.
There are roumors that this cave is visited with an ultralight airplane or an helicopter. They start at the landing strip below the mountain, and fly right through the cave. It is even possible to land inside the cave, which allows the passengers to have a look through the cave and out of the two portals. It seems this is only a computer game, and the pictures are faked. All reports of cavers and biologists who visited the cave tell that they climbed up or upseiled from the plateau. Nevertheless it is possible to fly around the tower and see the cave from both, ultralight and helicopter.
Cueva del Cerro Autana is also a famous mineral location, with chalcedony, opal, and sveite, for which it is the type locale. Sveite (KAl7(NO3)4Cl2(OH)16·8H2O) is a monoclinic nitrate. It was first collected by members of the Sociedad Venezolana de Espeleogia, here in the cave, and named after the acronym SVE. But as the whole area is proctect, it is strongly recommended not to start mineral collecting.