A Tangaroan eruption needs to satisfy two conditions – apart from occurring in a submarine environment. Firstly, she says, it requires the right speed of eruption: “too fast and the magma gases will come out of solution explosively, too slow and the gases will be lost from the magma and a dome will form.” Secondly, the water density has to be just a little higher than that of the rising blebs to allow them to rise.
Although this is the first time such an eruption style has been documented, there is evidence to suggest that others may well have occurred elsewhere: Rotella points to studies which identified similar types of pumice deposits and to anecdotal evidence of large pumice blocks appearing on the sea surface.
Implications of the Research
The research raises interesting questions about our understanding of volcanoes and their eruptions. “We propose Tangaroan eruptions to be a distinct eruption style (unique to the subaqueous environment) that could be viewed as on a continuum between explosive and effusive subaqueous eruptions,” explains Rotella.
“There quite possibly may be other ‘types’ of subaqueous eruptions, or variations of Tangaroan eruptions, which are yet to be discovered.”
Perhaps the most notable feature of this new eruption type is that it illustrates how little we know of Earth processes, especially those which are hidden from our view. “What else is there left to discover?” asks Rotella. “I would venture to say quite a bit. In quoting Richard Arculus’ 2012 Nature Geoscience paper, ‘The topography of the surface of Mars in known in greater detail than that of the Earth’s oceanic crust…’”
Rotella, M.D., Wilson, C.J., Barker, S.J. and Wright, I.C. Highly vesicular pumice generated by buoyant detachment of magma in subaqueous volcanism. (2013). Published online in Nature Geoscience. Accessed 28 January, 2013.