Researchers, presenting at the European Geosciences Union conference, investigate whether glacial retreat-related landslides trigger volcanic eruptions.
Prof David Rothery, Professor of Planetary Geosciences at The Open University, said:
“Major volcanic collapses are very rare, but the geological record shows that they can be locally catastrophic with a reach of several tens of km. This new research nicely demonstrates that if you change the load on a volcanic mountain – for example by removing some ice – the likelihood of a mechanical collapse and possible ensuing eruption will be slightly increased.
“Eruptions are triggered by a complex array of factors. I suspect that many eruptions caused by glacial melting might happen eventually anyway, given enough time – but this research shows that warming could increase the chances of those eruptions happening sooner rather than later.”
Dr David McGarvie, Senior Lecturer in Volcanology at The Open University, said:
“There are two main ‘ice’ scenarios to consider; ice-capped stratovolcanoes such as those that dominate the South American and Western USA; volcanoes beneath large ice sheets, such as those in Iceland and Antarctica.
“Several recent studies have looked at the case for increased eruption activity from ice-capped stratovolcanoes at end of the last glacial period about 12,000 years ago and have come up with no hard evidence that these volcanoes experienced any substantial amount of increased eruption frequency, volume etc.
“Conversely, there is more and better evidence across Iceland that when the ice sheet underwent major reduction at the end of the last glacial period, there was a large increase in both the frequency and volume of basalt erupted – with some estimates being 30 times higher than the present day.
“Some recent studies have tested the hypothesis that increases in ice melting over the past few decades have affected magma/eruption productivity in Iceland. At best, these studies weakly support this hypothesis, and there are equally valid (but more boring) alternative explanations.
“As more studies are done in Iceland, with better equipment (and hence better data), I would not be surprised to see more robust and convincing evidence of increases in magma production and/or eruptions in Iceland as the current ice caps shrink further. However, it’s quite a different matter melting a long-lived massive ice sheet up to 1.5 km thick that covers over 70% of the land surface (as happened at the end of the last glacial period), from melting isolated and much thinner ice caps/sheets that only cover about 11% of the land surface (i.e. present-day).”
Alison Graettinger, Assistant Professor of Geosciences at the University of Missouri, said:
“The abstract proposes that a landslide at Mt Meager has the potential to trigger a volcanic eruption, not just melting glacial ice. The abstract doesn’t have the room to provide more information on how the melting of glacial ice has weakened part of the volcano, leading to an increased potential for a landslide. Thus the link to climate is less direct than proposing as ice melts more volcanoes erupt. This makes the question ‘will a warmer climate and melting ice lead to more volcanic eruptions’ harder to answer. In order for a volcanic eruption to be triggered by a decrease in load (weight of ice or mass of rock) the magma chamber also needs to be ready to erupt. This means that decreasing ice volumes due to climate change will not cause volcanoes to erupt that were not close to eruption anyway. Ice on your classic stratovolcano is thinner than ice in ice caps, such as in Iceland, and the melting alone will have less impact on the volcanic system than in areas where ice is thicker. Because of the conditions that need to be met for this scenario to work it means that even if a few volcanoes were to be pushed towards eruption from ice melting, or landslides related to melting of ice, it would not be all ice clad volcanoes, nor even all volcanoes under thick ice. The study proposes that Mt. Meager may be one such volcano, but the study merely points out the potential, and not that all the conditions mentioned above have been met.”
* ‘Can glacial retreat-related landslides trigger volcanic eruptions? Insights from Mount Meager, British Columbia’ by Gioachino Roberti et al. was presented at the EGU conference on Wednesday 11 April.