Cueva del Cerro Autana

Cueva de Autana - Autana Cave

Useful Information

Location:	South of Puerto Ayacucho, Gran Sabana, Federal Amazonas. (4.858133, -67.448869)
Open:	no restrictions. [2024]
Fee:	free. [2024]
Classification:	Quartzite Karst Caves Lower Precambrian sandstones and quartzites of the Venezuelan Guiana Shield
Light:	n/a
Dimension:	L=395 m, H=40 m, A=1,150 m asl.
Guided tours:	self guided
Photography:	allowed
Accessibility:	yes, if you are able to board the helicopter
Bibliography:	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.
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History

1971	first explored by Charles Brewer-Carias and Robert Madden.
1978	Cerro Autana declared a Natural Monument.

Description

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 a plateau around 1,200 m asl, and as the surrounding plains are only 200 m asl, that's about one kilometer higher than the plains. The tower has vertical walls which are about 800 high and a steep and rather small foot of colluvium.

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 is the tepui. The sandstone is eroded at the foot of the cliff, the debris at the foot is transported away, as fast as the wall continually loses 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 unique: erosion from two sides cut through an erosional cave inside the rock. This has led to a huge portal, a natural bridge, a huge through-cave going through the enormous mountain. This cave passage is almost 400 m long and 40 m high.

Many of these erosional caves are found in the quartzite plateaus. They are told 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 abseiled 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 protected, it is strongly recommended not to start mineral collecting.