https://www.reddit.com/r/askscience/comments/1j7ftip/does_global_volcanic_activity_follow_cycles_or/
created by Notoriouslydishonest on 09/03/2025 at 19:44 UTC
107 upvotes, 3 top-level comments (showing 3)
I was looking at the list of large volcanic eruptions[1] and I noticed that the 19th century stands out as being unusually active. There were five eruptions with a VEI of 6 or greater between 1815 and 1912, compared to just two in the 113 years since then and one in the 200 years prior.
1: https://en.wikipedia.org/wiki/List_of_large_Holocene_volcanic_eruptions?wprov=sfla1
Is that just a random coincidence, or are there forces which affect volcanic activity on the global scale?
Comment by CrustalTrudger at 10/03/2025 at 13:36 UTC*
52 upvotes, 2 direct replies
There have been arguments that there might be cyclicity to global volcanic activity, but not at the temporal scale you're considering. I.e., there are a variety of suggestions that volcanic activity may vary in concert with Milankovitch cycles[1] (e.g., Schindlbeck et al., 2018[2], Kutterolf et al., 2019[3] or the preprint from Longman et al[4]), so on tens of thousands to hundreds of thousand year timescales. The argument basically is that melting of ice sheets during interglacial periods reduces loads on portions of the crust which may in turn increase magma production rates or influence magma storage in volcanic systems, leading to more and/or more productive eruptions from existing volcanic systems. There is however, at least to my knowledge, no suggestions of periodicity on shorter millennial to decadal timescales (at a global scale), and as such, the explanation for what you're seeing is simply the stochastic nature of most natural processes, i.e., yes, the differences in the record over the last few hundred years reflect randomness.
1: https://en.wikipedia.org/wiki/Milankovitch_cycles
2: https://www.nature.com/articles/s41598-018-22595-0
3: https://www.sciencedirect.com/science/article/pii/S0277379118301768
4: https://www.researchsquare.com/article/rs-3954094/v1
Comment by ExcelsiorStatistics at 11/03/2025 at 19:44 UTC
9 upvotes, 0 direct replies
There were five eruptions with a VEI of 6 or greater between 1815 and 1912
Note that you have cherry-picked the dates of Tambora and Katmai in choosing your century. If you just counted by centuries the 19th and 20th centuries would look about the same. If you were to randomly scatter 20 eruptions across 10 centuries (we expect about 1 big eruption per 50 years) you expect one or two centuries to get lucky and have no eruptions, and one or two centures to have four or five.
Comment by ThinNeighborhood2276 at 11/03/2025 at 08:28 UTC
3 upvotes, 0 direct replies
There is no clear evidence of global volcanic activity following strict cycles. While certain periods may appear more active, this is generally attributed to random distribution rather than predictable patterns.