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Andrew Alden

Xeno-Pumice: When Volcanoes Turn Fry Cook

By January 9, 2013

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xenopumicexenopumiceSeagoing researchers raced to the Canary Islands in 2011 when an eruption began off the volcanic island of El Hierro. On arrival, they began to collect these weird floating rocks. Most of us would say "Cool, pumice!" on seeing these, but the experts said "Hmm" and "uh-oh" instead. It was the white filling—was it a sign of rhyolite, a threat of unexpectedly explosive lava? It was not; instead it was a nice scientific puzzle whose solution is a new word for the lexicon: xeno-pumice. They're melted, puffed-up seafloor sediments in a fresh lava shell. See my new article for more details on this stuff.

Geologists, especially after a long day in the field, think about rocks in terms of food. These xeno-pumice bombs look like they ought to be edible, with their black-chocolate shells and cakelike interiors. They're something like frybread, except that the outer shell is a different material from the pith. I hope that they inspire some way-new cuisine chef, because I can't think of an exact duplicate from the world's kitchens.

See Also:
Etna blows smoke rings
Recipes for volcanoes
Geology and food items
Images from Troll et al. 2012, Solid Earth (open access)


May 6, 2013 at 6:52 am
(1) Alessio Di Roberto says:

For completeness of what has been said in the article I would like to add that there are two new interpretations of the origin of xenopumice, both reported in high rated scientific journals.
In the first paper by Meletlidis et al xeno-pumice are interpreted as resulting from the interaction (heating) between the basanitic magma feeding the 2011-12 eruption, a stagnant trachytic magma pocket and an associated halo with hydrothermally altered rhyolitic composition.
In the second work carried out by Sigmarsson et al the xeno-pumice are interpreted as the results of a gas-rich melt basanitic that remobilized a small volume of stagnant rhyolitic melt formed by incorporation approximately 10% of quartz-rich sediment into a late
differentiate of trachytic melts.
Both works show data testifying a probable origin of the xeno-pumices from rock that are not sedimentary.

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