The volcanic material could be from expanded perlite

The volcanic material could be from expanded Perlite

ANA SANTANA / EFE

The fragments emitted by the submarine eruption in El Hierro may contain perlite inside that has expanded, ie white volcanic glasses rich in silica and high water content, which suffered a natural expansion process and if confirmed this hypothesis, could be the first time you see this phenomenon.

This was stated by the geologist Juan Jesús Coello (Efe) in an interview in which he said that as far as he knows, this material has not been described in previous eruptions in the Canaries or the rest of the world.

The geologist indicates that the products released to date by the underwater eruption in the southern ridge of El Hierro are bits floating on globe shape, decimeter-sized, lightweight volcanic glass.

Some of the fragments have a protrusion or bulge of keel elongated way and according to chemical analysis conducted by the universities of La Laguna and Barcelona, ​​and the Center for Scientific Research, the crust is formed by a volcanic glass which is transparent, and dark brown basaltic composition, called sideromelana.

The interior consists of two types of volcanic glasses the first, opaque black, basaltic and has also called taquilita.

The second, which forms the bulk of the total volume of the floating fragments, is a vesicular volcanic glass snow white to gray-white.

Its composition is that of a trachyte or rhyolite, with 65 percent or more by volume of silica, a soft texture and a lower density than water.

Juan Jesús Coello indicates that this silica-rich volcanic glass could come from the natural expansion of volcanic materials originating from previous eruptions and deposited on the seabed near the current point of emission.

The expansion would have been produced by the release in the form of vapor, water molecules present in these materials, and would have been caused by an abrupt warming after they accumulated on basaltic lava fragments originating from the ongoing eruption.

For the chemical composition of this glass and the environment in which the eruption, geologist considered more likely the hypothesis that the material is an expanded perlite.

The main feature of perlites, which are named for their bright shiny circular fracture, is its high content of water molecules, from 2 to 6 percent by volume.

Perlite would have formed on the seabed by the hydration of volcanic glass called hialoclastita. The hialoclastitas are glass splinters breakage caused by magma coming into contact with water and cooling suddenly.

For artificial expansion the beads are crushed to the desired grain size and then subjected to rapid heating in industrial furnaces, until they reach temperatures between 760 and 890 degrees Celsius.

The beads have a multitude of applications: filtration processes, thermal insulation, improved growing media and inert fillers, among others.

In the case of those issued by the eruption in El Hierro it would be a natural expansion process, not artificial, which occurred at a pressure of 20 to 30 atmospheres from -200 to 300 meters deep. The water content of perlite molecular suffered natural expansion in the seabed of La Restinga can be quite higher than that expand artificially.

Other materials that could have produced this white glass similar expansion are zeolites, hydrated silicates whose name, Greek for "Zeos" boil, and "lithos," stone, derived from steam and becomes more swollen when heated, a property called intumescence.

Like perlite, zeolites are common products of the alteration of volcanic glass.

In any case, the geologist indicates that this is an unconfirmed hypothesis, so it is too early to assess the potential significance of this phenomenon.