Atlantis Tunnel

Atlántida Tunnel is the name given to the last section, completely flooded by sea waters from the La Corona volcanic tube, in the north of the island of Lanzarote (Canary Islands), in the municipality of Haría. The Cueva de los Verdes and Jameos del Agua, famous tourist centers on the island, are part of the same volcanic tube. The cave is located in the north of the island of Lanzarote (Canary Islands) and is of great geological and biological importance, housing at least 36 endemic species of the island of Lanzarote, of great evolutionary interest.

Origin and geological description

The Atlantis Tunnel was formed approximately 21 millennia ago in subaerial conditions and was subsequently flooded during the last transgression by waters of marine origin. The total length of the tunnel is approximately 1600 m long and it is the largest volcanic tube submarine of the planet. The flow that gave rise to the cave was emitted by a lateral hornite of the Corona volcano, and flowed in a southwest direction, probably in favor of some ravine bed. The sea level, being lower at that time, allowed the flow to advance approximately 2 km beyond the current coastline, on a coastal platform. The flow stopped when it came into contact with the water, with the sudden cooling of the lava. With the end of the last ice age and the retreat of the ice in northern Europe, the sea level rose, flooding the last section of the cave, which today we know as the Tunnel of Atlantis.

The Atlántida tunnel has two sections that run in parallel: a main section (Atlántida Tunnel) and an upper section of smaller length and diameter (Hidden Lake). The total length of the cave is 1600 m; with an average depth of 30 m and a middle section of 15-20 m. The tube ends at a depth of 64 m.

The main section of the Atlántida Tunnel begins at the Jameo Chico de los Jameos del Agua, with an entrance lake of ca. 10x10 m and a depth of 9 m. The bottom presents large blocks and an important accumulation of picon. The artificial lighting present in this part of the cave fades after a few meters, but allows algae to grow on the walls of the entrance. After a short section of 129 m and an average depth of 10 m, the first restriction (“the Chasm”) is reached where the section of the cave narrows and drops to 25 m. In this section there are two connections with the upper gallery, Lago Escondido, which runs in parallel over this section of the cavity. The cave then continues for about 250 m, where there is a second restriction in which the depth drops to 30 m. The cave then continues with a middle section of 15 m in diameter until reaching the Jable Mountain, an accumulation of ca. 20 m high calcareous sediments from outside. In this area, the marine influence in the cave is more evident, possibly due to the lower thickness of the rock layers that separate the cavity from the coastal waters. It is possible to observe in this section some sessile organisms, as well as some typical species of marine caves (e.g. Athanas cf.nitescens; Stenopus spinosus). After the Jable Mountain, the cave widens, reaching up to 25 m in section in some sections, and continues, with a descending depth, until the final widening, prior to the collapse of the cavity, at 81 m deep.

The upper section of the cave or Hidden Lake has an extension of 390 m and communicates with the Atlantis tunnel at three points, at 50, 130 and 200 m penetration. The section of this section is narrow and the bottom is covered by calcareous crusts, without large collapse blocks. This section ends with the progressive narrowing of the roof of the cavity.

The water column of the Tunnel is not stratified and has characteristics similar to seawater, except for a higher concentration of silicon. The salinity is 35.822 ‰ and the oxygen concentration is 4.89 ml/l. The water column is relatively stable and does not present turbulence, except for the presence of tidal currents, with a speed of 0.5-2.5 m/s. The organic matter throughout the cave's water column is allochthonous and of marine origin, and is introduced into the cave by these currents. Primary production is only recorded in the first meters of the tunnel, near Jameo Chico, due to artificial lighting.

Fauna diversity and ecology

In addition to its geological importance, the Atlantis Tunnel is part of the anchialine belt of Lanzarote, one of the most diverse anchialine ecosystems in the world with 36 endemic species. The following table summarizes the species cited so far for the cave. The inventory is supported by recent reviews and some new publications. Species that so far are only known in anchialine environments of Lanzarote (not necessarily only within the Tunnel) are indicated as endemic. The references section includes the most relevant quotes about the species in the cave, except for the original description.

History of cave exploration

The first exploration dates back to 1972, when the Guerra brothers reached 370 m.

In 1983, speleodivers from the STD in Madrid explored 1,570 m of the tube. The results of the expedition were summarized in a general inventory of the fauna of the Tunnel and the description of the first remipede, Speleonectes ondinae.

In 1986, a team of Franco-Belgian divers reached 1,618 m, the point where the tunnel ends at a depth of 64 m.

In 1987 an STD team again reached the scanning tip and confirmed that there was no continuity.

In 2008, a team of American divers from Texas A&M University, with the support of biologists from the University of Hamburg and the University of La Laguna, reached 1000 m of penetration and collected samples that led to the description of three new species, including a second remipede Speleonectes atlantida, and the so-called Meganerilla of César Manrique, Meganerilla cesari. The diving team was composed of Thomas M. Iliffe, Terence Tyssal, Jill Heinerth and James Rossi, along with non-diving scientists Renee Bishop (Penn State University), Stefan Koenemann (University of Veterinary Medicine Hannover), Alejandro Martínez (University of La Laguna) and Horst and Ulrike Wilkens (University of Hamburg)

In 2011, a team of Canarian divers organized by the University of Copenhagen and supported by the Cabildo of Lanzarote, achieved a comparable goal and collected samples that were studied by scientists from 8 universities around the world. The diving team was made up of divers Alejandro Martínez, Enrique Domínguez, Luis E. Cañadas, Sergio González and Ralf Schoenermark. The maximum penetration mark was the Jable Mountain, at 750 m.

In February 2019, with the Sublantida Project, a UNED research team, led by Javier Lario, reached, after 32 years, the exploration tip at -64 m depth to collect samples for the first study geological in the Antlantida Tunnel.,