Pumice raft

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Bimssteinfloß between the Tonga islands Late and Vava'u added to the MODIS of NASA .

Pumice rafts are collections of pumice stones that float on the sea due to their density. They arise from underwater volcanic eruptions just below the water surface and from explosive volcanic eruptions on islands or near the coast.

Emergence

During explosive volcanic eruptions, in which viscous lava is foamed by water vapor and volcanic gases. As soon as this foamy mass escapes from the volcanic vent, it cools down quickly, and the porous pumice is created. The resulting pumice has extremely small openings, if they are wetted by water, the water forms a film due to its surface tension, which encloses the gas contained in the pores and thus prevents it from soaking. However, this is offset by a process that lasts much longer: the gas gradually diffuses through the surface of the water and escapes, which increases the density of the rock and thus makes it sink. This diffusion can take years, which in turn explains the longevity of the pumice stone carpets floating in the sea.

hazards

Pumice rafts are primarily a danger to shipping, as they can damage ships or cut off ports from the rest of the sea. After the outbreak of Krakatau in 1883 , Indonesia was cut off from world trade because pumice rafts clogged the Sunda and Java Seas. Since 2014 there has been an initial approach to describe pumice rafts using simulations and thus possibly predict their distribution.

Origin of life

Pumice stone rafts are one possible piece of the puzzle in the creation of life. Pumice has a large surface and can absorb a lot of hydrocarbons and other substances. In addition, a concentration gradient can occur in pumice stone rafts , because the pumice receives low-salt rainwater from above and salty seawater from below at the same time . A pumice stone raft receives energy from lightning and solar radiation .

See also

Web links

Individual evidence

  1. ↑ Horst Rademacher: Floating stones: islands made of volcanic foam . In: Frankfurter Allgemeine Zeitung . 2017, ISSN  0174-4909 ( faz.net ).
  2. ↑ Ships should be better warned about volcanic rocks. Researchers have succeeded in predicting the route of floating volcanic rock. That could make shipping safer - and make it easier to find other flotsam. In: Zeit Online. Zeit Online GmbH, April 22, 2014, accessed on April 22, 2014 .
  3. ↑ a b Foam-Born Life. (No longer available online.) In: Planet Erde. Archived from the original on March 3, 2016 ; Retrieved April 22, 2014 .