Can climate change affect earthquakes and volcanic eruptions?

Over the past 14 weeks or so, we have moved from looking at hurricanes to floods to droughts and to bushfires. The links between climate change and these natural disasters have been relatively more apparent and there is a massive pool of literature that has been dedicated to these disasters. In this penultimate post of my three-month long project, we shall explore the links between climate change and earthquakes and volcanic eruptions. I have actually been looking forward to writing this blogpost ever since this project started given that unlike the other natural disasters, volcanic eruptions and earthquakes have not been commonly associated with recent climate change. I have been eager to find out if there are indeed any credible theories that suggest that recent/future climate change has/can affect the frequency and intensity of earthquakes and volcanoes. So let’s begin!

Credits: European Geosciences Union and Associated Press

While doing my research, I found that one of the strongest proponents of this topic has been Prof Bill McGuire from UCL, who published the book ‘Waking the Giant: How a changing climate triggers earthquakes, tsunamis and volcanoes’ back in 2012. The video below summarizes his points from the book:

There has actually been very little peer-reviewed journal papers that discuss the links between recent climate change and earthquakes/volcanic eruptions. The papers that do have mostly been published in the Philosophical Transactions of the Royal Society in its Theme Issue ‘Climate forcing of geological and geomorphological hazards’. Hence, in this post, I will be basing my analyses on the book by McGuire as well as several journal articles from the themed issue mentioned above.

Given that climate change is mostly associated to changes in the atmosphere and hydrosphere, it might be a little far-fetched to some that climate change would affect the geosphere. However, if we look to the past, there is evidence that climate change has indeed affected the frequency and intensity of volcanic eruptions and earthquakes. After the Last Glacial Maximum, rapid warming caused a major reorganisation of the global hydrological cycle as the continental ice sheets melted and resulted in sea level rise of the order of >100m. The unloading of mass through the melting of ice reduced the pressure on the crust and induced significant stress changes in the crust. Modifications of the pattern of stress and strain triggered volcanic and seismic activity, marine landslides and tsunamis that were of much greater intensity than those in the present climate (McGuire 2010). Meanwhile, the loading of mass in the oceans basins as water is transferred from the ice sheets into the oceans can also alter stress patterns and trigger earthquakes. Podolskiy (2009) highlights the case of the Caspian Sea, which underwent a natural rapid rise in water level of 235cm between 1978 and 1995. This rapid filling of water increased the weight on the basin within a short period of time and caused a number of earthquakes on its coastline.

Likewise, changes in the distribution of ice and water around the world also have consequences on volcanic activity. Volcanoes erupt when the pressure increases past a tipping point as the magma builds up from within. Hence, events that cause changes in stress can affect the pressure build up within the volcano and trigger an eruption. The retreat of ice sheets and ice caps, causing the reduction in pressure on the crust, can provide this trigger (Palgi and Sigmundsson 2008). It is posited that the decompression of the crust would reduce the pressure at depth in the mantle, promoting melting and the generation of magma (Sigmundsson et al. 2010). This might have caused volcanic activity to be ten times more frequent in Iceland just after the last glacial period, just as the ice sheet that covered Iceland melted (Sigmundsson et al. 2010). Moreover, recent studies on the Vatnajökull ice cap have suggested that recent thinning under the present warming climate has produced an additional 0.014km³/year of magma under Vatnajökull (Pagli and Sigmundsson 2008).

However, the critical question is whether under present/future climate change, will there be an increase in the seismic and volcanic activity as seen in the past glacial/interglacial transition periods? Indeed, the present climate is nowhere similar to the post-LGM period, however, McGuire (2012) speculates that present and future climate change would be sufficient to induce a geospheric response. At present, small ice masses are already thinning and retreating, as with the Vatnajökull ice cap, resulting in load pressure reductions of 0.5MPa or more (Sauber et al. 2000; Tuffen 2010). Meanwhile, according to the IPCC AR4 report, the projected sea level rise will range from 0.18 and 0.59m. A 0.59m of additional water mass would correspond to a 5.7kPa increase in pressure on the crust in the ocean basins (Podolskiy 2009). Although these changes are relatively small, both in terms of absolute values and rates, McGuire (2010) argues that there is a growing body of evidence to show that small changes in environmental conditions can still trigger seismic and volcanic activity. This includes Hainzl et al. (2006) that suggested that at times when the Earth’s crust is so close to failure, pore-pressure variations of less than 1kPa caused by heavy rainfall is enough to trigger earthquakes.  

The areas of greatest concerns are those at the higher latitudes or altitudes in excess of 4000m (Tuffen 2010). At these areas, ice bodies are still present and hence should they continue to undergo melting and recession under a warming climate, they might be able to create changes in patterns of stress and strain and induce seismic responses. Moreover, as the ice sheets that buries volcanic systems such as the Vatnajökull, or ice caps found on volcanoes such as Kilimanjaro disappear by the end of the century, it is worried that the decompression might induce mantle melting and cause more frequent eruptions.

As shown above, the links between climate change and volcanic eruptions and earthquakes seem to be apparent. Indeed, there is a consensus among the scientific community that climate change had affected the frequency and intensity of seismic and volcanic activity in the past, especially during glacial/interglacial transitions. However, it is important to note that the hypothesis that future climate change would have similar impacts on the geosphere have received a lukewarm response thus far. This is most likely due to the fact that we are uncertain of the sensitivity of the geosphere to small changes in ice thickness and ocean loading (Tuffen 2010) and hence are still not totally convinced that future climate change would be sufficient to affect patterns of volcanic eruptions and earthquakes.

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This marks the last two categories of natural disasters that I will be covering as part of this series. Phew, we have come a long way! Check back next week as I do a wrap up for the project and look back at what we have done these past few months!