Melting glaciers in North America 10,000 years ago may have given continental drift a bit of a push. Similar activity in Greenland now could eventually trigger volcanic eruptions in Iceland.
Geoscientists modeled a chain of events that demonstrate how sea level rise impacts plate tectonics, they report in the journal Nature.
“As ice volume was greatly reduced, it caused a huge motion in Earth’s crust,” Tao Yuan, a graduate student at Colorado University, Boulder, and an author of the paper, said in a press release. “Scientists knew that the ice melting caused the plates to uplift. But we show that they also moved a lot horizontally due to the ice melting.”
Ice Melting and Plate Tectonics
The geoscientists based their simulation’s start at 26,000 years ago, when the Laurentide Ice Sheet, which covered much of North America, started receding. Melting ice raised sea levels just under half an inch a year, they calculated.
This global thaw may have sped up the tectonic plate on which much of North America sits by up to 25 percent between 12,000 years and 6,000 years ago. The melt may have also increased the rate at which the North American and Eurasian plates spread apart by as much as 40 percent.
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Rethinking Continental Drift’s Speed
The study may cause us to rethink the speed at which plate tectonics occurs. The process has long been considered a slow, leisurely (dare we say glacial?) one. Shorter bursts of activity — at least on a geological timescale — may also have important impacts on how the planet reshapes itself in the future.
“That story that we’ve been telling for a long, long time — that processes like seafloor spreading and continental drift operate at timescales of millions of years driven by Earth’s internal engine, thermal convection,” Shijie Zhong, a CU, Boulder physics and co-author of the paper, said in a press release. “That’s still true, but we show that glacial forcing can also cause significant motion on relatively short timescales of 10,000 years.”
The simulation especially focused on the Mid-Atlantic Ocean Ridge — the area where the North American and Eurasian tectonic plates meet. That feature runs through the middle of the Atlantic Ocean and cuts through Iceland. Movement from the two plates allows magma from deep within the planet to bubble up. As the molten rock cools into a solid, the pressure slowly forces the plates that hold North America and Europe farther apart.
Implications for Iceland
The textbook rate that many scientists have held as a consensus was just under an inch a year over the past two million years. The new simulation shows there might be some fluctuations in that speed, depending on how fast glaciers melt, sea levels rise, and perhaps other factors.
For now, the speed at which Greenland’s ice sheet is melting doesn’t appear to be increasing the rate of the planet’s continental drift. However, if the melt accelerates — a distinct possibility if the planet’s rate of warming continues to increase — it could still impact Iceland within the next several hundred years.
“Ice sheets in Greenland and West Antarctica are still melting,” Yuan said in the release. “We think the ice melting could enhance seafloor spreading and volcanism at nearby mid-ocean ridges in the future.”
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Before joining Discover Magazine, Paul Smaglik spent over 20 years as a science journalist, specializing in U.S. life science policy and global scientific career issues. He began his career in newspapers, but switched to scientific magazines. His work has appeared in publications including Science News, Science, Nature, and Scientific American.
