Predicting the apocalypse, like other growth industries, is subject to fad. The hot new one is making irresponsible arguments about geological upheaval based on an uptick in volcanic activity. “You may not have noticed, but our planet is becoming increasingly unstable,” writes doomsday prophet Michael Snyder on InfoWars, noting that 40 volcanoes are currently erupting around the globe. Tearing apart cynical alarmism is fun so let’s dive in on his line of argumentation.
Snyder bolsters his claim that this is a particularly large amount of activity with some funny math: “There were a total of 3,542 volcanic eruptions during the entire 20th century. When you divide that number by 100, that gives you an average of about 35 volcanic eruptions per year. So the number of volcanoes that are erupting right now is well above the 20th century’s average for an entire calendar year.”
But a volcano can remain active for hundreds, even thousands of years, so it’s a fallacy to compare total eruptions with current eruptions. And how you count depends on how define a volcano and how you classify an active volcano. The Smithsonian Institution’s Global Volcanism Program doesn’t even count eruptions as discrete events, instead it counts numbers of volcanoes to show activity within a time frame. It’s normal to have 50 to70 active volcanoes within the span of a year and about 20 at any particular point in time. The institute counts exactly 20 active volcanoes right now.
The historic data for volcanic eruptions actually does show a clear upward trend over time, but this is due to reporting bias, explains Lee Siebert, director of the Global Volcanism Program. Basically, the more humans there are on the planet, the closer attention they are paying to volcanoes and the more eruptions reported. The only two times in modern history reported eruptions fell were during the first and second world wars, which sort of proves the point.
When you look instead at the rate of major eruptions — ones big enough to capture attention even in the midst of global social strife — the trend line has stayed flat over time.
But levels of global volcanic activity can and do fluctuate. Volcanoes are produced by shifts in Earth’s tectonic plates, which make up a system that is chaotic (difficult to predict, like the weather) but not random (impossible to predict, like a coin flip). Scientists are learning more and more about the complicated ways that geological process can impact volcanism, and how eruptions might be affected on short and long time scales.
Even human-induced climate change, as it turns out, could eventually lead to an increase in global volcanic activity. A growing body of research suggests that more volcanoes will erupt in areas that used to be covered in ice, because of the significant amount of weight lifted off of the continents, which had been keeping a lid on the seismic activity. However the weight of ice lost in one region will be added as water in another — the overall effect is complicated and uncertain.
It is certainly true that changes in volcanic activity lead to changes in climate. Global warming may also lead to increased volcanic activity, but the evidence to date is still thin. It could be thousands of years before today’s disappearing glaciers force a measurable increase in eruptions, if that occurs at all.
Here’s another thing that some scientists think might impact global volcanism: Tiny shifts in the speed of rotation of the planet. We like to think of the length of a day on Earth as a constant thing, although in fact it varies. The variances are on the order of fractions of milliseconds, and they are caused by multiple factors, including the motion of Earth’s core.
One study found a significant relationship between change in the length of a day and volcanic activity. It takes a huge amount of energy to speed up or slow down the Earth’s rotation, and some of the energy might be stored as stress between tectonic plates and released in an eruption. The researchers note that a change in the Earth’s rotation could therefore result in increased volcanic activity, but that volcano eruptions could also trigger changes in the length of day because of the resulting changes in the atmosphere. This is pretty cool, but the change in level of volcanic activity is subtle and temporary — falling well short of the predicted volcanopocalypse.
The bottom line is that, on any timescale relevant to your life, the current level of volcanic activity is and will continue to be within the realm of normal. Anyone who tries to tell you differently is probably trying to sell you something.