Underground 'supercave' stretches nearly 16.5 miles, with a 3,000-foot vertical drop

Explorers in southern Spain have linked two deep caves into one “supercave system” about 16.4 miles long. The connection sits inside Sierra de las Nieves near Málaga and pulls together years of careful mapping by volunteer cavers and collaborating scientists.

The work was led at the Underground Exploration Group of the Excursionist Society of Málaga. Its team focuses on systematic cave mapping and safe access to complex systems.

Early surveys suggest the connected network could eventually extend to roughly 31 miles if nearby passages link up.

The new supercave complex also incorporates a known water cave, which hints at a larger underground drainage story. That makes the system a valuable natural laboratory for water tracking in limestone mountains.

For Andalusia, the find marks a step change in underground science and hazard planning. Long cave networks can reveal how floods move through rock during heavy rain.

Linking two caves into a supercave

Teams spent decades mapping passages, measuring angles, and plotting profiles. They worked methodically from both sides until survey lines converged in a narrow zone.

This is patient speleology – the scientific exploration of caves. It blends rope work, precise instruments, and record keeping to turn darkness into a reliable map.

Recent pushes focused on overlooked side routes and tight chimneys that earlier parties bypassed. That careful rechecking paid off when two galleries finally met.

The project shows why you revisit old data with fresh eyes. Small positional errors can hide a junction for years until improved surveys tighten the picture.

What the rocks reveal

Sierra de las Nieves is a high relief limestone massif where water sculpts voids over time, a setting documented by a geomorphology analysis.

Here, fractures in the bedrock guide underground development. Water seeks the easiest path along cracks that eventually widen into rooms and shafts.

As galleries grow, they connect into a branching network. That network moves storm pulses from uplands to springs, shaping the region’s water budget.

Supercave mapping adds missing pieces between recharge zones and outflow points. Better maps support models that predict where water, silt, and pollutants will travel.

Life in the dark

Caves shelter specialized animals that live in constant night. Biologists call them troglobionts, organisms adapted to caves with reduced eyes and pigment.

The broader landscape holds UNESCO Biosphere Reserve status, which covers fragile karst habitats and their wildlife.

These communities depend on steady temperatures and scarce nutrients. Disturbance can ripple through food webs built on bat guano, microbes, and drips.

Protecting supercave means limiting traffic, light, and noise. It also means keeping mud and lint off formations that took millennia to build.

Rules and respect underground

Park managers were notified after the breakthrough, and cave visits in protected areas require prior authorization. That point is reinforced in the regional bulletin.

Permits help control group sizes, routes, and timing. They also track cumulative impacts on sensitive chambers and seasonal bat roosts.

Good practice never goes out of style. Teams pack out every scrap, minimize footprints, and leave scientific markers for follow up work.

Safety is part of stewardship. Clear callout plans and redundant gear keep rescuers out of harm’s way and reduce pressure on public services.

What comes next

The connection opens years of work for geology, hydrology, and biology. Researchers will test airflow, water chemistry, and rock stability as the system is mapped.

Future campaigns will target junctions where small side tubes might bridge to neighboring caves. Each new survey leg will be checked against earlier line plots.

The team will also refine vertical profiles. Accurate elevation data clarifies how stormwater drops through shafts before joining the main drainage.

Lessons from the supercave

This is classic karst, terrain formed by dissolving rock such as limestone. Acidic water finds fractures, enlarges them, and eventually builds caves.

In time, the system records climate history in minerals that grow from drips. Those records help scientists place recent rainfall swings in a longer frame.

Supercaves teach teamwork and data discipline. They also show how surface choices, from paving to pumping, can echo underground for a long time.

The new complex turns hidden space into a map that anyone can read. It is a reminder that science thrives on patience, precision, and shared notes.

—–

Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates. 

Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.

—–