Restless Hekla: an update 7 July 2011

The global news machine showed much interest in Hekla yesterday, but little interest in getting the facts right, or indeed the volcano right. Many supposedly reputable news outlets followed AFP’s lead and boldly illustrated their reports on Hekla with a picture of Eldfell, which is many miles to the west on Heimaey Island. AFP even labelled their picture of Eldfell ‘The Hekla volcano on Heimaey Island’, for pity’s sake. You’d think the presence of the sea in the picture of Eldfell would have given it away, Hekla being some distance inland, but apparently not. To help journalists and editors get it right I’ve provided pictures of the two volcanoes above, and obtained the assistance of a passing seven-year-old in providing labels so clear that even Daily Mail journalists will grasp the difference.

There was considerable interest in Hekla yesterday, but media speculation notwithstanding, all is quiet there today and the activity appears to be subsiding. Hekla is closely-monitored and we’ll be as well-informed about what it’s doing as we are about any volcanoes anywhere. In the meantime, it’s best not to jump the gun and read too much into every episode of seismic restlessness.

The forecasting of volcanic eruptions is fraught with uncertainty. Volcanoes, unlike earthquakes, generally give some signal of their intentions in the form of seismic activity, inflation, gas emissions and so on, but working out what those signals mean is no easy matter, and even the most sophisticated analysis of the widest possible range of data can never do more than reduce the level of uncertainty, it can never remove it altogether.

Likewise, a particular volcano’s history is an important guide to current and future behaviour, but no matter how full and detailed our knowledge of a volcano’s past may be, it is not an infallible guide to that same volcano’s future. Significant patterns can emerge from the records we have of a volcano’s previous activity, in terms of eruptive style and periodicity, but they can never be more than indicative. You can’t say, for example, that because volcano ‘A’ turns out to have erupted roughly every ten years since 1970, and it is now 11 years since its last eruption, that a big bang is imminent. Nor can you argue that because the geological record for volcanic field ‘B’ shows eruptive activity about every 2000 years and it is now 5000 years since we last had a peep out of it, it is ‘overdue’ and we should be worried. Human beings like patterns, and we particularly like periodicity: it provides a structure for our understanding of the past, and we like to use it to make some sense of the future too. But it has to be considered alongside other evidence and cannot offer anything but a set of pointers.

For volcanoes a knowledge of the chronological pattern of activity only gets us part of the way to understanding what is going on at any given moment, and what is likely to happen within the next month, year, decade or century — and it can never be definitive. Hekla has a volatile history and is active and restless, and will erupt again, but we do not know when: it could happen tomorrow, or next year, or in ten years or twenty (there was a gap of 23 years between the 1970 eruption and its predecessor in 1947, and 57 years between that eruption and the one before that in 1913, so the ten-year cycle is a pretty recent development anyway). It is not ‘overdue’. Nor is it ‘ready to erupt’:* we’ll know when it is ‘ready to erupt’ because it will then erupt.

* Did Páll Einarsson actually use this phrase? And if he did (in Icelandic), has the meaning he intended been faithfully reproduced (in English translation) by the news sources that have seized upon the phrase? In the past Dr Einarsson has not always been well-served by the way his comments have become distorted in translation or otherwise misrepresented: see examples from October 2009 and February 2011.

Information
Global Volcanism Program: Hekla – summary information for Hekla (1702-07=)