Study suggests link between sea level and eruptions
European researchers say they’ve found more evidence supporting links between climate change and volcanic activity.
Geologists from Switzerland, France and Spain studied compared data on eruptions and climate from about 5 million years ago, finding that volcanic activity in southern Europe doubled during a time when the Mediterranean Sea dried up. They suspect that the changes on the surface contributed to the way magma behaves deep in the Earth.
The era they studied is known as the Messinian salinity crisis, when the Strait of Gibraltar was blocked and the Mediterranean temporarily isolated from the Atlantic, according to the study published in Nature Geoscience.
The geological record shows a sharp increase in volcanic activity, and the scientists concluded the spike can best be explained by the almost total drying out of the Mediterranean.
The trait of Gibraltar was shut on a temporary basis during the Messinian Era (from 5.96 to 5.33 million years ago) and that the Mediterranean Sea was isolated from the Atlantic. Thick layers of salt on the seabed, as well as river canyons carved through land that is now submerged, suggest the Mediterranean Sea’s level was much lower.
The study acknowledges that this hypothesis continues to be a source of debate, while exploring the potential links.
In a statement, University of Geneva geologist Pietro Sternai said it’s clear that changes at the surface of the Earth, like a sudden lowering of sea level, can change the pressure deep down around pockets of molten magma. Based on that, the researchers studied the changes in volcanic activity during the period. Tracing the age of crystals in volcanic deposits, they counted 13 eruptions around the Mediterranean between 5.9 and 5.3 million years ago — more than double the average over comparable time periods.
Why is the figure so high?
“The single logical explanation is the hypothesis that the sea dried out, since this is the only event powerful enough to alter the Earth’s pressure and magmatic production over the entire Mediterranean,” Sternai said.
The team used computer models to simulate the effect of the Mediterranean’s desiccation on pressure at depth and the impact on magma production. According to Sternai, the models show the only way to account for the increased vulcanism was that the level of the Mediterranean Sea dropped by about two kilometres.
Related research has suggested that melting ice sheets in the polar regions, as well as melting glaciers, could also contribute in various ways to increased volcanic activity.