Instability of the Cumbre Vieja slope

The instability of the Cumbre Vieja slope is a developing geological emergency off La Palma, where worm colonies and their associated bacteria are advancing through methane hydrates beneath a volcanic flank. It turns a proposed rescue operation into a new source of danger: removing the infestation may not be possible without disturbing the seabed it has already weakened. The slope’s uncertain condition links the earlier Norwegian collapse to a second, still unresolved threat, in which a local intervention risks setting off a much larger failure.

Background and warning signs

The concern begins with the relationship between the worms, bacteria and hydrate. On the Norwegian continental slope, worms and bacteria had transformed stable hydrate icefields and veins into porous, brittle remnants. Their disintegration released methane, fractured surrounding rock and helped trigger a vast chain of seabed collapses. The Cumbre Vieja flank is feared to be vulnerable to a related process, although the precise state of the hydrates and the conditions needed to initiate a collapse remain uncertain.

On August 14, Gerhard Bohrmann watches the sea from the Heerema, a large semi-submersible platform stationed off La Palma. He knows that millions of worms carrying billions of bacteria are moving through thin hydrate veins about 400 metres below. The platform’s stability and manoeuvrability make it suitable for the operation, but they cannot remove the underlying uncertainty: clearing the worms may not undo their effects if bacteria have already spread into the hydrate.

Bohrmann is particularly troubled by the possibility that the flank may already be close to failure. Even if the worms are removed, the team cannot establish how many bacteria have entered the ice. He fears that collapse may be too advanced to prevent, and imagines a huge dome of water rushing toward the platform. Yet he continues to hope the operation will work and that the yrr might be persuaded to repair damage as well as cause it. His hope is expressly conditional: neither the state of the slope nor the possibility of recovery is known.

The removal operation

The Heerema’s equipment is built for a sustained, technically demanding operation. Two cranes at the front of the platform handle a suction tube and a separate lighting unit equipped with cameras. Technicians coordinate the equipment from elevated control cabs. The lighting unit, a ten-metre scaffold of pipes and struts linked to the platform by fibre-optic cable, is lowered first so the team can inspect the seabed before directing the tube toward the infestation.

On the monitors, the operators see a jagged wall of lava and a terrace-like protrusion. A nearby ridge is covered with wriggling worms. The view is limited to the forty metres picked out by the floodlights, so the team cannot assume it represents the entire flank. Bohrmann’s first reaction is that they have arrived too late; he then checks that fear against what remains unknown. The worms may or may not have deposited enough bacteria to cause serious harm, and the final trigger for a collapse is not established. The uncertainty makes delay dangerous, but it also means that the threatened catastrophe is not yet confirmed.

The tube operates for sixteen hours, sucking up worms by the tonne. Many do not survive the rapid change of environment, while the rest are collected in nets and carried by conveyor into a freighter beside the platform. The initial success changes what the cameras reveal: once the sediment settles, they show marbled lava crossed by rising bubbles. Bohrmann identifies the pattern as bacterial mats and points out grey lines representing hydrate. The visible evidence is mixed. Some hydrate remains, but the team cannot tell how much was present originally or how much has already dissociated. Methane levels in the water are above average, though not yet at a critical level.

From intervention to renewed danger

The crew continues to move the tube and lighting scaffold northward, following readings from the Polarstern expedition that suggest the infestation is confined to the terrace. Bohrmann estimates that clearing the worms will take at least a couple more days. If the worms and bacteria can be removed, he thinks partially eroded hydrates may have a chance to restabilise. That prospect depends both on the limited extent of the infestation and on the damaged hydrate retaining enough stability to recover.

The operation then encounters a more immediate danger. Bohrmann notices something glittering on the screens and orders the tube moved. The operator reports that it is drawing up large chunks of material and becoming unstable. Bohrmann recognizes the situation as resembling the earlier blowout aboard the Sonne, but this proves to be a different and worse problem: the suction has lingered over one part of the terrace and is tearing up sediment as the plateau comes loose.

A cloud of sediment expands and a pressure wave rocks the scaffold. The pump is switched off, but debris continues to fall from above. Bohrmann sees lava boulders crashing onto the terrace and understands that cracks spreading through the near-vertical flank could detach larger and larger masses. Because the lava is porous, a small slide could become an avalanche within minutes—the very kind of escalation the operation is meant to avert. The equipment’s proximity to the slope, necessary for removing the worms, has placed the team in the path of a potentially expanding failure.

Unresolved consequences and significance

The scene ends without confirming whether Cumbre Vieja collapses. Bohrmann sees the slide developing and fears that the crew has no time to escape; his mind returns to the imagined dome of water rising hundreds of metres into the sky. This is an anticipation of disaster, not a report that a tsunami has occurred. The slope’s condition remains uncertain, and the account leaves the operation at the moment when a local disturbance could become an avalanche.

That uncertainty carries the memory of the Norwegian catastrophe. There, hydrate disintegration released gas across 150 kilometres of slope, set off successive failures, and generated a tsunami that devastated northern European coastlines. The earlier disaster establishes the possible scale of a cascade, while the Cumbre Vieja episode shows that the same broad threat cannot be treated as a simple, controllable engineering problem. Removing worms might help preserve the remaining hydrates, yet suction itself can destabilize the terrain; visible bacterial mats, surviving hydrate and elevated methane offer evidence, but not a reliable forecast.

The slope therefore occupies two roles in the crisis: it is an ecosystem already altered by the worms and bacteria, and a geological system whose response to intervention may be nonlinear. The team’s knowledge is detailed but incomplete. They can observe the infestation, identify mats and hydrate, and detect the onset of movement, yet cannot determine how much damage preceded their arrival or whether the slide can be contained. The unresolved state of the flank makes the operation a race against both the infestation and the consequences of trying to remove it.