Methane gas craters discovered off coast of Christchurch, New Zealand

This forms part of an article by Robertscribbler, Concern Over Catastrophic Methane Release — Overburden, Plumes, Eruptions, and Large Ocean Craters

Giant Craters on the Seabed 

off the coast of New Zealand

In 2013, marine geophysicist Dr Bryan Davy from GNS Science found what may be the world’s largest gas eruption craters on the seafloor about 310 miles east of Christchurch, New Zealand.

(Giant craters off Christchurch New Zealand are thought to have formed due to large gas eruptions during previous episodes of sea bed warming. Could human warming set be setting off something similar for the Arctic? Image source: Mysterious Giant Crater Like Structure Found Near New Zealand.)

The craters, which the researchers called ‘pockmarks,’ formed in an active gas zone along the ocean bottom. They measured from 250 meters to 7 miles in diameter and about 300 feet deep. With the largest crater able to encompass all of lower Manhattan.

The craters are thought to have formed during ice ages when sea levels lowered off New Zealand causing the sea bed to warm and gas hydrate to thaw. Eventually, the gas is thought to have erupted into the surrounding water with a portion bubbling up into the atmosphere.

GEOMAR seismic records indicated active gas pockets beneath the crater zones. Dr Joerg Bialas, a GEOMAR scientist noted:

Gas release from the larger pockmarks may have been sudden and possibly even violent, with a massive volume being expelled into the ocean and atmosphere within hours or days.

The 300 foot depth of the craters touched the hydrate stability zone even as their large size indicated that massive pockets of the gas lifted away large sections of sea bed suddenly and violently. It’s the kind of rapid destabilized gas release that may well represent a worst-case Arctic warming scenario.

Cause for Appropriate Concern

So the question must be asked — is the Yamal crater physical validation of a catastrophic methane hydrate release mechanism that has circulated, as theory, through the geophysical sciences for decades? One that involves large eruptions that displace massive sections of earth and seabed during a violent release process. Are the Siberian methane blowholes smaller examples of what can happen on a much greater scale? And does the methane overburden in the Arctic, the documented increasing Thermokarst Lake release, the sea bed methane release in the Laptev and ESAS, and the new formation of methane blow holes in Yamal in the context of a rapidly warming Arctic tundra and sea bed (seeing unprecedented rates of warming) represent a growing risk for this kind of release?

Under even a ‘moderate’ 1 to 3.5 gigaton Arctic carbon release rate by end century given by the survey of 100 Arctic scientists, there will likely be more than enough potential freed methane to include large scale catastrophic releases similar to the kind seen off New Zealand and elsewhere (250 meter to 7 mile wide cratering events).

In this context, the issue is not one of ‘apocalypse now’ or ‘apocalypse not.’ That framing is all wrong. This issue is one of how much or how little geophysical upheaval and related methane release we will see — and how soon. One of how rapidly humans can stop making the situation even worse, by drawing down their own catastrophic emission rates as rapidly as possible.

There is, therefore, more than enough cause for appropriate concern and continued monitoring of what appears to be an ongoing destabilization of Arctic carbon stores — large enough to represent a variety of hazards both terrestrial and atmospheric.