The human drive to explore leads us to the planet’s most inaccessible places, including the vast, lightless voids beneath the surface. Speleology, the scientific study of caves, documents these subterranean environments. A “deep cave” is defined not by its total length, but by its maximum vertical dimension—the difference in elevation between the highest entry point and the lowest explored passage. This challenging frontier reveals Earth’s inner architecture and pushes the limits of human endurance.
The Current Record Holder
The title of the world’s deepest known cave belongs to Veryovkina Cave, an immense vertical system located in the Arabika Massif. This mountain range, part of the Gagra system in the Western Caucasus, is situated in Abkhazia, a region known for its highly developed karst topography. The cave’s officially confirmed depth is 2,212 meters (approximately 7,257 feet).
Veryovkina’s true scale remained largely unknown after its initial discovery in 1968 by Soviet speleologists. Major breakthroughs occurred much later, when Russian caving teams from the Perovo Speleo Club launched extensive expeditions. These efforts dramatically extended the known depth, culminating in the March 2018 expedition that reached the terminal sump, establishing the current world record.
This achievement surpassed the previous record holder, Krubera Cave, which is located in the same Arabika Massif and had a maximum depth of 2,199 meters. These two caves are the only known systems on Earth that plunge more than two kilometers beneath the surface. Veryovkina’s exploration is characterized by narrow, water-choked passages and massive vertical shafts, making the descent a multi-day undertaking even for experienced cavers.
Defining and Measuring Vertical Depth
Establishing a verifiable world record for cave depth requires precision and a clear technical definition. Depth is measured along the Z-axis, representing the maximum vertical distance between the highest natural entrance and the lowest point reached by explorers. This measurement is distinct from the cave’s total length, which is the cumulative distance of all explored passages.
To achieve accuracy, speleologists rely on sophisticated digital surveying tools, such as laser distance meters integrated with compasses and inclinometers. These instruments, often referred to as DistoX devices, measure the distance, azimuth, and inclination of each passage segment. Surveyors record thousands of data points, which are then processed using specialized software to create a three-dimensional model of the cave system.
The highest and lowest surveyed points are then used to calculate the precise vertical separation, providing a definitive depth figure that meets international standards. This rigorous methodology is essential for maintaining the integrity of caving records and ensuring that explorations are accurately mapped.
The Geology Driving Extreme Cave Formation
The creation of ultra-deep caves like Veryovkina depends on a rare convergence of specific geological factors. The most fundamental requirement is a thick, homogeneous layer of soluble rock, most commonly limestone, which provides the raw material for dissolution. This rock layer must be massive enough to allow water to penetrate and dissolve the rock over a tremendous vertical span.
A second factor is significant tectonic uplift, which elevates the limestone layer high above the regional water table and sea level. In the Arabika Massif, the massive Gagra Range provides the necessary high-altitude platform, creating a large vertical drop for water to exploit.
The final component is the presence of abundant water, typically from snowmelt and rainfall, which becomes slightly acidic as it absorbs carbon dioxide from the soil. This mildly acidic water, a weak carbonic acid, seeps into vertical fractures and bedding planes in the limestone. Over millions of years, the relentless, slow dissolution process carves out the vertical shafts and passages.