Why the pending eruption hasn't started

One reason why the Sundhnúkagígar crater row has not yet erupted, despite the fact that the volume of magma under Svartsengi is greater than was estimated for the last eruption, is that in each eruption and magma run, the horizontal pressure that holds the magma chamber grows. Thus, more pressure is always needed to overcome the tension in the earth's crust.

This is what Páll Einarsson, professor emeritus of geophysics at the University of Iceland, said in Dagmál of Mbl.is yesterday.

"There is much in this scenario that we can learn from. For example, it is not uncommon for the pressure in this magma chamber to exceed its previous high. So these breaking limits, when the tank breaks and empties itself, they change and they rise over time," Einarsson says.

This happened 20 times in Krafla and has happened seven times in Svartsengi.

"If there is a rule to things, this is the rule. It usually rises to the previous height, until that time we have a so-called safe period. After that we have a period of uncertainty. This period of uncertainty can be very long."

To begin with, it can be short, he explains, and then it can be longer as the events become more numerous.

No one dared to declare the end of Krafla eruptions

The last volcanic eruption in Krafla lasted for fourteen days in September 1984.

"We saw that the magma influx decreased as the sequence progressed. But it was also scary. It was not steady. Sometimes there was a considerable influx, but sometimes almost nothing, and it could be that way for quite a long time," Einarsson says.

"What caused the end of the Krafla eruptions not to be declared yet was that the magma accumulation at the end was higher than it had ever been before. As such, the magma chamber stopped receiving material, but in a high state. So the pressure in that was higher than ever before. The sequence of events stopped there.

It could never be completely ruled out that there would be some kind of geological accident and it would erupt from this chamber. Because there was enough pressure for that, but the restraint was stronger. The inflation didn't stop until 1989, 15 years after it started. Even then, no one has dared to declare that Krafla will not erupt from this magma chamber. So people may have to wait a bit for the end of the fires from Svartsengi to be declared. "