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Sea Floor Volcanoes May Be Unseen, But They Are Affecting Global Climate

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Volcanoes on the Earth's sea floor can pulsate and periodically erupt, potentially altering climate around the globe, new analysis reveals.

Geologists traditionally believed that undersea volcanoes erupt slowly, releasing lava at a controlled rate. But, new research shows these formations, found in mid-ocean ridges, erupt on a regular basis, with periods between two weeks and 100,000 years. Strangely, these eruptions take place almost entirely during the first half of the year. Investigators believe these events are caused by small variations in the orbit of the Earth.

Volcanic eruptions could have a major effect on the Earth's climate, researchers determined.

"People have ignored seafloor volcanoes on the idea that their influence is small - but that's because they are assumed to be in a steady state, which they're not. They respond to both very large forces, and to very small ones, and that tells us that we need to look at them much more closely," Maya Tolstoy from the Lamont-Doherty Earth Observatory, managed by Columbia University, said.

Mid-ocean ridges stretch for 37,000 miles across seafloors around the globe. Chains of volcanoes expel lava, pushing the seafloor apart, resulting in continental drift. Tolstoy's team determined that this action, thought to be nearly constant over time, are currently erupting at a reduced rate, compared to their average rate.

Underwater volcanoes produce eight times as much lava as volcanoes on Earth, and their chemistry is different from similar features on land. However, differing chemical makeups of volcanoes on the land and under the sea result in approximately equal releases of carbon dioxide, roughly 97 million tons annually.

Milankovitch cycles are periodic changes to the axial tilt of the Earth, as our planet oscillates between tilts of 21.5 and 24.5 degrees every 41,000 years. Other periodic changes in Milankovitch cycles, including one lasting 100,000 years, also play a role in warming and cooling the planet. Tolstoy believes this effect could be tied in with the periodic eruptions of undersea volcanoes. However, the exact cause of these eruptions remains unclear, as the process is extremely complex.

Ice caps on land may press down on volcanoes, reducing the occurrence of volcanic eruptions on the land, some geologists theorize. However, as ice melts, this pressure could be relieved, leading to the release of lava, as well as carbon dioxide into the atmosphere, resulting in additional warming and ice melt, Tolstoy theorizes. Undersea volcanoes could exhibit the opposite behavior - water trapped in ice during cooling periods lower sea levels, which may relieve pressure on volcanoes on the ocean floor. Carbon dioxide released by eruptions there could start to warm the planet, researchers believe.

"The most interesting takeaway from this paper is that it provides further evidence that the solid Earth, and the air and water all operate as a single system," Edward Baker from the National Oceanic and Atmospheric Administration (NOAA) said.

Investigation of undersea volcanoes and their potential role in the environment were detailed in the journal Geophysical Research Letters.

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