Scientists turn textbook volcanic eruption theory on its head

Washington: Researchers have recently revealed that volcanoes theory shown in the typical textbooks might not be exactly correct.

Researchers at Caltech and the University of Miami in Florida found that the volcano pictures, such as those that are forming the Hawaiian Islands, illustrate that it erupts when magma gushes out as narrow jets from deep inside Earth but those pictures are wrong.

Don Anderson, the Eleanor and John R. McMillian Professor of Geophysics, Emeritus, at Caltech said that new seismology data are now confirming that such narrow jets don't actually exist.

He further explained that, in fact, basic physics doesn't support the presence of these jets, called mantle plumes, and the new results corroborated those fundamental ideas.

It was mentioned that no one has been able to detect the predicted narrow plumes, although the evidence has not been conclusive. The jets could have simply been too thin to be seen. Very broad features beneath the surface have been interpreted as plumes or super-plumes, but, still, they're far too wide to be considered narrow jets.

But now, due to more seismic stations spaced closer together and improved theory, analysis of the planet's seismology was good enough to confirm that there are no narrow mantle plumes. Instead, data reveal that there are large, slow, upward-moving chunks of mantle a thousand kilometers wide.

The new measurements suggested that instead of narrow jets, there are broad upwellings, which are balanced by narrow channels of sinking material called slabs. What was driving this motion was not heat from the core, but cooling at Earth's surface.

The results also have an important consequence for rock compositions, notably the ratios of certain isotopes.According to the mantle-plume idea; the measured compositions derive from the mixing of material from reservoirs separated by thousands of kilometers in the upper and lower mantle. But if there are no mantle plumes, then all of that mixing must have happened within the upwellings and nearby mantle in Earth's top 1,000 kilometers.

The study titled 'Mantle updrafts and mechanisms of oceanic volcanism' is published in the Proceedings of the National Academy of Sciences.