By Ignacio A. Jara
It has been widely documented that volcanic aerosols can alter the radiative balance of the atmosphere, producing measurable temperature depressions following large explosive eruptions. Perhaps the most renowned of these cases is the eruption of the mount Tambora in Indonesia, which in 1815 caused a decline of 0.5°C in the Northern Hemisphere in what was known as “the year without a summer” (1).
But, what if this causal relationship is inverted and climate change affects the number of volcanic eruptions?
In 1979 Rampino et al., first used proxy data to argue that periods of climate cooling were associated with catastrophic volcanic events such as the latest Taupo eruption in New Zealand or the mega eruption of the Toba volcano in Indonesia (~70,000 cal yrs) (2). The authors boldly proposed that the changes in ice extent and sea level during glaciations resulted in sufficiently large variations in the Earth’s crustal stress to alter volcanic activity over longer time scales.
Since this pioneering study, a considerable number of publications have added local evidence supporting long-term climate variations as a driver for volcanic activity. However, solid evidence pointing to a definitive link between glacial cycles and volcanism at global scales as remained elusive.
An interesting article published in 2012 adds new insights into this theory. They analysed the timing of more than 400 tephra layers identified in marine sediment records around the Pacific “Ring of Fire” over the last 1 Myr (3). The spectral analysis of tephras deposited off South and Central America, Japan, the Philippines and the Southern Pacific islands reveals that periods of increased volcanic eruptions have a recurrence of 41 kyr, the exact periodicity of the Earth’s obliquity. Moreover, phase analysis indicates that peaks in volcanic eruptions lag behind minimum ice volume and maximum sea level by about 4 kyr.
Since obliquity has been recognized as one of the orbital pacemakers of the Pleistocene ice ages, these results indicate a direct link between orbital cycles, glacial/interglacial climate and global volcanism. The authors further suggest that this link could be mediated by surface pressure variations resulted from ice-ocean mass redistribution during periods of abrupt climate change. In this regard, volcanic eruptions along the edge of continental plates are expected to occur at greater frequency during periods of deglaciation, when ice retreat caused crustal pressure to decrease, lowering the compression of the rock overlying the magma chambers.
Undoubtedly these results are preliminary and much more work is required to better understand this phenomena. Even though the duration of the present-day warming trend is several orders of magnitude quicker than climate variations presented here, the interplay between climate change, ice extent and volcanism might be relevant in high-latitude regions with ice caps and active volcanic zones. As the atmosphere heats up at an unprecedented rate, the removal of large ice loads may contribute to the reactivation of volcanic complexes or the emergence of unknown volcanic systems.
1. K. R. Briffa, P. D. Jones, F. H. Schweingruber, T. J. Osborn, (1998) Influence of volcanic eruptions on Northern Hemisphere summer temperature over the past 600 years. Nature 393, 450-455.
2. M. R. Rampino, S. Self, R. W. Fairbridge, (1979) Can rapid climatic change cause volcanic eruptions? Science 206, 826-829.
3. S. Kutterolf, M. Jegen, J. X. Mitrovica, T. Kwasnitschka, A. Freundt, P. J. Huybers, (2012) A detection of Milankovitch frequencies in global volcanic activity. Geology, (doi: 10.1130/g33419.1).