Lifestyle & Travel

Mar 1, 2015

Closer to the Center of the Earth

Krubera Cave or Voronya Cave, is the deepest known cave on Earth. It is located in the Arabika Massif of the Gagra Range of the Western Caucasus, in the Gagra district of Abkhazia, a breakaway region of Georgia. 

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The difference in elevation of the cave's entrance and its deepest explored point is 2,197 ± 20 metres (7,208 ± 66 ft). It became the deepest-known cave in the world in 2001 when the expedition of the Ukrainian Speleological Association reached a depth of 1,710 m (5,610 ft) which exceeded the depth of the previous deepest known cave, Lamprechtsofen, in the Austrian Alps, by 80 m. In 2004, for the first time in the history of speleology, the Ukrainian Speleological Association expedition reached a depth greater than 2,000 m, and explored the cave to ?2,080 m (?6,824 ft). Ukrainian diver Gennadiy Samokhin extended the cave by diving in the terminal sump to 46 m depth in 2007 and then to 52 m in 2012, setting successive world records of 2,191 m and 2,197 m respectively. Krubera remains the only known cave on Earth deeper than 2,000 metres.

"Voronya Cave" means "Crows' Cave" in Russian. This name was used as a slang name by Kiev speleologists during the 1980s due to a number of crows nesting in the entrance pit, and then remained in the literature and media as a second name for the cave. The original name "Krubera" had been assigned to the cave by Georgian speleologists who explored the entrance pit in 1960. This name was given after the noted Russian geographerAlexander Kruber. The name "Krubera Cave" thus has a priority.

The Arabika Massif, the home of Krubera (Voronya) Cave, is one of the largest high-mountain limestone karst massifs in the Western Caucasus. It is composed of Lower Cretaceous andUpper Jurassic limestones that dip continuously southwest to the Black Sea and plunge below the modern sea level.

To the northwest, north, northeast, and east, Arabika is bordered by the deeply incised canyons of Sandripsh, Kutushara, Gega and Bzyb rivers. The Bzyb River separates Arabika from the adjacent Bzybsky Massif, another outstanding karst area with many deep caves, including the Snezhnaja-Mezhonogo-Iljuzia System (?1,753 m or ?5,751 ft) and Pantjukhina Cave (?1,508 m or ?4,948 ft). To the southwest, Arabika borders the Black Sea.

The Arabika Massif has a prominent high central sector with elevations above the tree line at ~1,800–1,900 m (5,900–6,200 ft). This is an area of classical glaciokarstic landscape, with numerous glacial trough valleys and cirques, with ridges and peaks between them. The bottoms of trough valleys and karst fields lie at elevations of 2,000–2,350 m (6,560–7,710 ft), and ridges and peaks rise to 2,500–2,700 m (8,200–8,900 ft). The highest peak is the Peak of Speleologists (2,705 m (8,875 ft)) but the dominant summit is a typical pyramidal horn of the Arabika Mount (2,695 m (8,842 ft)). Some middle- to low-altitude ridges covered with forest lie between the central sector and the Black Sea. A plateau-like middle-altitude outlier of the massif in its south sector is Mamzdyshkha, with part of the plateau slightly emerging above the tree line.

Among several hundred caves known in the Arabika Massif, fifteen have been explored deeper than 400 m and five deeper than 1,000 m.

Krubera Cave is located at 2,256 m asl in the Ortobalagan Valley, a perfectly shaped, relatively shallow, glacial trough of the sub-Caucasian stretch, which holds the advanced position in the Arabika's central sector relative to the seashore. Since 1980, Ukrainian cavers have been undertaking systematic efforts in exploring deep caves in the Ortobalagan Valley, resulting in exploration of the Krubera Cave to its current depth and of the Arabikskaja System to depth of ?1,110 m (?3,640 ft). The latter consists of Kuybushevskaya Cave (also spelled as Kujbyshevskaja; ?1,110 m) and Genrikhova Bezdna Cave (?965 m to the junction with Kujbyshevskaja). Another deep cave in the valley, located in its very upper part and explored by Moldavian and Ukrainian cavers is Berchilskaya Cave, 500 m (1,600 ft) deep. All large caves of the Ortobalagan Valley likely belong to a single hydrological system, connected to large springs at the Black Sea shore. The direct physical connection of Krubera Cave with the Arabikaskaja System is a sound possibility, although not yet physically realized.

The core part of the Arabika Massif is composed of the Upper Jurassic succession resting on the Bajocian Porphyritic Series, which includes sandstones, clays and conglomerates at the top, and tuff, tuff sandstones, conglomerates and breccia, porphyry and lava. The Porphyritic series forms the non-karstic basement of Arabika, which is exposed only on the northern and eastern outskirts, locally in the bottoms of the Kutushara and Gega River valleys. In the central part of Arabika the Cretaceous cover (Valanginian and Hauterivian limestones, marls and sandstones) is retained only in a few ridges and peaks, but it lies intact through the low-altitude ridges to the south-west of the central part. There the Cretaceous succession includesBarremian and Aptian–Cenomanian limestones and marly limestones with abundant concretions of black chert.

The Upper Jurassic succession begins with thin-bedded Kimmeridgian–Oxfordian cherty limestones, marls, sandstones and clays, which are identified in the lower part of Krubera Cave. Above lies the thick Tithonian succession of thick-bedded limestones with marly and sandy varieties. Sandy limestones are particularly abundant through the upper 1,000 m sections of deep caves of the Ortobalagan Valley.

The tectonic structure of Arabika is dominated by the axis of the large sub-Caucasian anticline (oriented NW–SE), with the gently dipping southwestern mega-flank, complicated by several low-order folds, and steeply dipping northeastern flank. The axis of the anticline roughly coincides with the ridge bordering the Gelgeluk Valley to the north. Located on the southwestern flank of the major anticline is another large one (Berchil'sky), in which the crest is breached by the Ortobalagan Valley. There are several smaller sub-parallel anticlines and synclines farther southwest, between the Berchil' Ridge and the coast.

The plicative dislocation structure of the massif is severely complicated by faults, with the fault-block structure strongly controlling both cave development and groundwater flow.[4] Major faults of the sub-Caucasian orientation delineate several large elongated blocks that experienced uplift with different rates during Pliocene and Pleistocene. This had a pronounced effect on the development of deep groundwater circulation and of Krubera Cave in particular. Both longitudinal and transverse faults and related fracture zones play a role in guiding groundwater flow, the latter guide flow across the strike of major plicative dislocations, from the central sector toward the Black Sea.

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