Roughly 1,000 active volcanoes dot our planet, and monitoring their rumblings is critical for forecasting future eruptions. But about 20% of those volcanoes already have an effective monitoring system in place, with nary a wire or sensor in sight, researchers have now suggested. Scientists recently showed that glaciers located near active volcanoes flow significantly faster than other glaciers. That discovery, which holds true in all glacierized regions except Antarctica, suggests that glaciers could be used to monitor volcanic activity, the team concluded.
“Changes in glacier characteristics might be indicative of changes in volcanic activity.”
The hazards associated with volcanism extend far beyond erupting lava—nearby populations can also be exposed to ground shaking, plumes of toxic gas, and clouds of ash, to name just a few dangers. But outfitting volcanoes with instruments that afford some advance warning of those threats is often challenging: Many volcanoes are located in remote areas, and volcanic landscapes are notoriously tough on sensors.
“It’s very difficult to monitor volcanoes,” said Joe Mallalieu, a glaciologist at the University of Birmingham in the United Kingdom.
But perhaps glaciers—which are found on or within a few kilometers (a few miles) of roughly one in five active volcanoes—might function as a surrogate of sorts when it comes to monitoring. “Changes in glacier characteristics might be indicative of changes in volcanic activity,” said Mallalieu, who completed this work while at Manchester Metropolitan University.
Going Global
To test that idea, which had previously been explored only in single-volcano or regional studies, Mallalieu and his team mined a global database of glaciers. The researchers homed in on 214,086 glaciers—2,729 of which were located within 5 kilometers (3 miles) of an active volcano. The team defined an active volcano as one that had likely erupted during the Holocene (i.e., within the past 12,000 or so years).
The researchers then used previously published estimates of glacier surface velocity, among a slew of other parameters such as precipitation levels, air temperature, and elevation, to study correlations between proximity to an active volcano and a glacier’s properties. That’s a worthwhile investigation, Mallalieu said, because glaciers can be readily monitored using satellites. “There’s an increasing number of datasets,” he said.
The team opted to focus on glacier surface velocity as the characteristic most likely to be linked to volcanic activity. That’s because volcanism is associated with heat, which tends to melt the undersides of glaciers, causing them to slide more quickly.
Heat Spikes
There’s always heat percolating throughout our planet’s crust due to processes like radioactive decay, said Ben Edwards, a volcanologist at Dickinson College in Carlisle, Pa., and a member of the research team. Background values might be in the ballpark of 50 milliwatts per square meter (per 10 square feet). But geothermal heat fluxes are typically substantially higher in places with active volcanism, Edwards said. “If you’re on an active volcano, that can jump up by somewhere between 100 and 1,000.”
“Glaciers that are located near active volcanoes flow approximately 50% faster than glaciers that are located elsewhere.”
Mallalieu and his colleagues showed that glaciers closest to volcanoes flowed significantly faster than glaciers that were more distal. That trend held true when the team considered either median or mean values of glacier surface velocity. “Glaciers that are located near active volcanoes flow approximately 50% faster than glaciers that are located elsewhere,” Mallalieu said.
Glaciers located near volcanoes tend to have slightly different properties than glaciers that are located elsewhere. The researchers made sure to control for these potentially confounding factors such as ambient air temperature, ice thickness, and glacier slope. Even factoring in these environmental and glacial characteristics, the researchers found that glaciers within 5 kilometers (3 miles) of volcanoes still flowed significantly faster than glaciers located more distally.
Furthermore, the team showed that glaciers located within 1 kilometer (0.6 mile) of an active volcano flowed about 30% faster than glaciers located 2.5–5.0 kilometers (1.5–3 miles) from an active volcano. Mallalieu and his collaborators concluded that the driver behind their results was indeed geothermal heating due to volcanism. These findings were published in Communications Earth and Environment.
These new results make sense, but it’d also be useful to collect more measurements of geothermal heating in the vicinity of active volcanoes, said Taryn Black, a glaciologist at the University of Maryland who was not involved in the research. “I don’t think that they conclusively showed that it is heat, because they didn’t provide any heat data.” And investigating other possible confounding factors is important, too, Black said. For instance, controlling for when precipitation is occurring and whether it’s falling as snow or rain would be valuable, she said.
Mallalieu and his colleagues hope that other researchers will test their conclusions. For instance, changes in a glacier’s velocity through time and over an area could be correlated with estimates of how magma is moving underground, Mallalieu said. “We think the next obvious step is to look at spatial and temporal patterns of glacier velocities.”
—Katherine Kornei (@KatherineKornei), Science Writer
Citation: Kornei, K. (2024) Glaciers near active volcanoes flow faster, Eos, 105, https://doi.org/10.1029/2024EO240491. Published on 14 November 2024.
Text © 2024. The authors. CC BY-NC-ND 3.0
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