Most people think of volcanoes as explosive cloud belching behemoths that interrupt air travel or end civilizations. Not many would think to look volcanoes underneath the sea, where 75 to 80 percent of all volcanic activity on Earth takes place.
But those deep-sea, mid-ocean ridges are home to plenty of volcanoes that are more likely to produce steady flows of lava than explosions.
However, over the last decade, geologists have speculated that based on certain evidence in the surrounding environment, these undersea volcanoes are capable of explosive eruptions. No one’s been able to prove it though. Until now.
Christoph Helo, a PhD student in McGill University’s Department of Earth and Planetary Sciences, has discovered extremely high concentrations of CO2 in droplets of magma trapped within crystals taken from volcanic ash deposits on Axial Volcano on the Juan de Fuca Ridge, off the coast of Oregon.
These droplets of magma, preserved within the crystals, represent the state of magma prior to eruption. As a result, Helo and other researchers from McGill University, the Monterey Bay Aquarium Research Institute, and the Woods Hole Oceanographic Institution, have been able to show that explosive eruptions can take place in deep-sea volcanoes.
On top of the discovery that the deep-sea volcanoes can erupt violently, the researchers also found that the release of CO2 from the deeper mantle to the Earth’s atmosphere is much higher than had previously been imagined, as a result of higher than assumed levels of carbon dioxide in the upper oceanic mantle.
Considering that these mid-ocean ridges are home to the largest volcanic system on Earth, even more active than the famed Ring of Fire which borders the Pacific Ocean, this discovery has important implications for understanding our planets carbon cycle, implications which before now had not been evaluated.