Beautiful Lake Taupo, New Zealand. The only hint of its volcanic origin are the distant volcanoes on the horizon, built at the edges of the ring fault system. (Provenance unknown)

When Is a Caldera a Caldera?

It does not take long for a newcomer to volcano-watching, if we are to call our hobby that, to come across the term “caldera”, cauldron. The term is very loosely used to describe large volcanic depressions ranging from volcanic craters a few hundred metres in diameter up to the huge depressions left behind by the…

Holuhraun

A Look at the Overall Picture

One of the more persistent reader questions is “What will/can happen now?”. I am pretty convinced that this question is what occupies most people on the inside of IMO, Allmannavarnir and NordVulk as well. The words of several eminent vulcanologists, that this episode is unprecedented, indicate that this may indeed be so. But in order…

Hand coloured image of the VEI-4 1918 eruption of Katla. It was the largest explosive eruption on Iceland during the last century, only the 2011 Grimsvötn eruption was larger.

Activity at Katla and Bárdarbunga

Lately the internet has been filled with the usual doom and gloom about Katla. And since there has actually been a bit of unusual behavior I find it merited to actually write about the volcano. Background on Katla The volcano resides under the Myrdalsjökull glacier and it is one of the larger volcanoes on Iceland.…

Truly spectacular Etna photograph by Giovanni Basso.

Waiting for Etna Part II & Riddles

While we are waiting for the expected fiery occurrence of Etnas Twentieth Paroxysm we can warm ourselves by watching expectantly the cams for Etna or go on a detour to Sakurajima. Or why not delve into the mysterious tremor encircling 20 percent of Iceland starting somewhere between Hekla and Katla reaching all the way around…

Hand coloured picture from the 1918 eruption of Katla.

Katla and the art of reading data

There are several factors that are monitored in an active volcano. For most Icelandic volcanoes the things that are monitored and are publicly available are tremor, earthquakes and GPS. In the case of Hekla there is also available mountain strain data from borehole strainmeters. For some volcanoes there are also periodic gas measurements taken and…