Ambrym Island’s famed lava lakes lost

Ambrym Island, Vanuatu / March 2019

The volcanic island of Ambrym, Vanuatu is certainly a wonder of the world. There isn’t another place like it anywhere on our planet. Two imposing cones rise from the desert-like caldera, both churning with molten rock.

I have made descents within both Marum and Benbow’s cones on multiple expeditions. Anyone venturing this close to the blazing lava has felt a blazing sense of mother nature’s disinterest in us. But then it all changed…

Unprecedented geological events unfolded in December 2018 which ultimately brought about the destruction of the famed lava lakes.

During my last expedition on the island, (Dec) I observed a number of anomalies. Both lava lakes were dramatically larger and Marum’s lake was particularly impressive with regular overflows. Adam, our guide, (acclaimed for climbing Marum over three hundred times) had not witnessed Marum like this. Ever.

The last ever footage of Marum’s lava lake (Dec 2018)

Furthermore, the Niri mbwelesu crater which had laid dormant for almost 20 years, morphed into a new lava lake within months.

The chamber beneath Ambrym was supplying an abundance of magma.

Niri mbwelesu. The birth of a new lava lake. (Jan-Dec 2018)

 

After making a number of successful observations, a dramatic increase in seismic activity followed on Dec 15. Within ten minutes, the lava lakes had drained. (Photo courtesy of John Tasso)

That afternoon, an intra-caldera fissure eruption occurred (near the Lewolembwi Crater), lasting approximately four hours. John Tasso, who has helped me on many expeditions, captured this extraordinary footage.

Eruptive plumes from both cones followed caused by the subsidence and collapse of the summit crater walls (from magma movement along the east-rift zone). Ground deformation measurements found a migration of magma from within the caldera towards the south-east of the Island (more than 20 km away).

Benbow crater eruption

Large fault line cracks opened in Paamal Village (eastern side of Ambrym)
Recent observations confirmed no emissions, nor presence of lava – however activity on the seashore did eject pumice. Vanuatu Geohazards believes the cracks were produced by a possible dyke that formed from the drainage of the main craters of Benbow and Marum.

The VMGD cam normally captures prominent glows from each crater. Tonight (and previous nights), there is nothing but darkness.

So what unfolded? Well, the changes are unprecedented. The intra-caldera area is hardly recognizable.

Changes to Benbow:

The changes observed in Benbow’s crater are the most dramatic. The inner tephra ring has collapsed entirely, falling into the ash cone and filling up the explosion pits. Benbow’s two active lava lakes have been buried beneath tonnes of slurry. There is a significant subsidence near the outer tephra ring.

Benbow’s crater today:

Changes to Marum:

A large area of the old Marum tuff cone and a location we often camped in, has collapsed and caved in. The main lava lake and active vent is now buried. The crater was about 1,000 feet (300 m) deep, however is significantly shallower now.

Other changes:

The other major change is a collapse to the northern crater wall of Niri Taten. Much of what is seen in the photo below has collapsed.

It’s likely these changes are not limited to observations made in the images above. An on-ground expedition is planned for April 2019.

The big question on everyone’s mind right now is when and if we’ll see the return of Ambrym’s famed lava lakes. For now, we wait patiently.

-Extreme Pursuit / March 2019

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