2022 started literally with a bang. The eruption of Hunga Tonga-Hunga Ha’apai was one of the most powerful explosions in decades, with some evidence that the jet it produced reached space. As impressive as the Tonga eruption could, could be, was part of our planet’s normal volcanic activity each year. So how volcanically active is the planet?
I get a lot of questions about whether Earth’s volcanic activity is increasing. Sometimes it can feel that way, especially when a big eruption hits the headlines and people start noticing other volcanoes. Just last month, Hawaii’s Mauna Loa began erupting again for the first time in nearly 40 years. When people discovered that Kilauea, right next to Mauna Loa, was erupting at the same time, there was always the question of whether this was normal. Based on records of volcanism on the Big Island, we know it is!
Mauna Loa erupts on December 8, 2022. Photo: USGS/HVO.
Fortunately, we don’t have to use anecdotal evidence to show that we’re not on an increasingly active planet. The Smithsonian Institution and USGS Global Volcanism Program documents all known volcanic activity around the world. Their database spans hundreds of thousands of years. They are also assembled Volcanism Weekly Review worldwide every week. It’s a treasure trove of volcanic goodness.
According to the last census of volcanic activity collected by GVP, there are 44 ongoing eruptions. I bet most people are surprised by that number. The media rarely covers most of this activity unless it is large, unexpected, deadly or harmful. That’s just how the news media works. So, lava flows in a remote volcano in Alaska such as Great Sitkin don’t get into the headlines.
How many eruptions?
In 2022, GVP has documented 82 eruptions (at 78 volcanoes). Of these, 31 were eruptions that started this year, another 38 have ended (some of which may have started this year), and the balance are eruptions that will continue into 2023.
In 2021, this number was 80 eruptions (on 75 volcanoes), with 33 new eruptions, 29 eruptions ended. Looking at 2020, there were 72 (out of 67 volcanoes), 27 new, 25 ending. You’re starting to get the idea. The number is remarkably stable when you look over the last 20 years.
Taking the numbers maintained by the GVP for eruptions since the 1960s, perhaps we can see a pattern there:
Chart showing eruptions since 1960, with (from top to bottom) active volcanoes, total eruptions, new eruptions, and eruptions ending. A trend line is shown for each value. Credit: Eric Klemetti with data from the Global Volcanism Program, 2022 [Database] Volcanoes of the World (v. 5.0.1; December 19, 2022). Distributed by the Smithsonian Institution, compiled by Wentzke, E.
Interesting! At first look, the trend line since 1960 for active volcanoes and eruption is slightly up. New eruptions starting each year are flat, and eruptions that end are slightly up.
Two hypotheses arise from this. The first could be that volcanic activity is increasing. The second may be that our awareness of volcanic activity is increasing. How could we know this?
Comparing the size of eruptions
We classify volcanic eruptions using Volcanic Explosivity Index. It is a crude tool that compares the volume of material produced in an eruption. It was developed to compare explosive volcanic eruptions, so those that produce mostly lava flows fit awkwardly into this index, commonly called the VEI. Eruptions that fall into VEI 0-3 are relatively small and occur frequently. For example, in 2021, 30 of the 80 eruptions documented by GVP were VEI 2. VEI 4 and larger eruptions are much less common, with only one VEI 6 eruption in the past 60 years.
If you want to argue that volcanic activity is increasing, you might expect that all types of eruptions are increasing. So what happens if we plot the eruptions by VEI (note: the GVP database sorts as VEI 2, 3, 4, 5 and 6+
Volcanic eruptions each year sorted by their Volcanic Explosivity Index (VEI), with VEI 2 (top), VEI 3 (middle), VEI 4 (bottom). VEI 5 and later are not included due to their scarcity since the 1960s. Credit: Eric Klemetti with data from the Global Volcanism Program, 2022 [Database] Volcanoes of the World (v. 5.0.1; December 19, 2022). Distributed by the Smithsonian Institution, compiled by Wentzke, E.
So the trend lines for eruptions since 1960 are pretty flat, especially for eruptions above VEI 2. This is something that GVP’s Ed Wentzke scored for the long-term database of volcanic activity spanning hundreds to thousands of years. The total number of eruptions appears to be increasing, but the number of larger eruptions remains flat.
Wentzke’s conclusion from this is that we are simply better at spotting flares. Large eruptions are much more noticeable from further away, so they add to the record. Before 1980, small eruptions below VEI 2 could only be seen if someone was standing right near the volcano at the right time.
If we take the GVP data a step further, we can really see this.
The number of eruptions by year, with those that would rank at VEI 0-1 above and VEI 2 or above. Credit: Eric Klemetti with data from the Global Volcanism Program, 2022 [Database] Volcanoes of the World (v. 5.0.1; December 19, 2022). Distributed by the Smithsonian Institution, compiled by Wentzke, E.
Look at this! Eruptions greater than VEI 2 are almost flat, while eruptions that are VEI 0-1 have a clear upward slope (increase) since 1960. The best explanation for this is that we have just managed to document more than these small eruptions. They were noticing More ▼ eruptionsbut the total number of eruptions is no increasing.
We just see a lot more
We can thank several major innovations for this ability to “see” more eruptions. The instruments for observing volcanoes — seismometers to record earthquakes, GPS to record shape changes, webcams (both visual and infrared), infrasound to record the deep shocks of an eruption — became better, more common, and widely used. We can monitor individual volcanoes more closely, and more countries have invested in volcano monitoring to protect people living near active volcanoes.
The other achievement is the global network of Earth observation satellites. In 1980, only a few weather satellites were able to capture the eruption of Mount St. Helens. Today, thousands of government and private satellites orbit the Earth’s surface every day. These eruptions of remote volcanoes such as Great Sitkin or Mount Michael in the Indian Ocean are noted and recorded, adding to our database.
The result is that eruptions that kill thousands of people are far less common now than in the past. All this information about volcanic unrest means that geologists monitoring volcanoes can give good advice to crisis managers, allowing people to get away safely.
For some, it may be exciting to think that the Earth is becoming more active, at least geologically. Climate change is leading to destructive weather events more often in the last quarter of a century. Fortunately, volcanoes have not (and will not) follow suit. Instead, we just have a lot of eyes (and tools) on the flares around the planet.