Get our newsletter!
Check out the volcano tours offered by Volcano-Adventures!
Volcanoes & Earthquakes - new app for Android
Guaranteed tours:
23 Dec 17 - 5 Jan 2018: Desert, salt and volcanoes - Danakil desert (Ethiopia)
30 Dec 17 - 6 Jan 2018: Nyiragongo Lava Lake & Mountain Gorillas - DR Congo + Rwanda
13-26 Jan 2018: Desert, salt and volcanoes - Danakil desert (Ethiopia)
28 Jan - 4 Feb 2018: Nyiragongo Lava Lake & Mountain Gorillas - DR Congo + Rwanda
17-23 Mar 2018: Kilauea Volcano Special - Big Island, Hawaiʻi
25-29 Mar 2018: Sakurajima Volcano Special - Kyushu (Japan)
28 Apr - 3 May 2018: Aegean's Hidden Gem: Isle of Milos - Milos Island (Greece)
5-13 May 2018: From Stromboli to Etna - Eolian Islands + Etna volcano (Italy)
19-27 May 2018: From Stromboli to Etna - Eolian Islands + Etna volcano (Italy)
9-17 Jun 2018: From Stromboli to Etna - Eolian Islands + Etna volcano (Italy)
: spaces available / : guaranteed / : few spaces left / : booked out

Support us?


Maintaining the volcano and earthquake news sections on this website, the free Volcano Webcams tool and interactive map widget is a free-time, both time- and server cost intensive effort.
If you find the information useful and would like to support us, and help keep it alive and improve it, please consider making a small donation. Thank you!
Random pictures

Illustrated Volcano Glossary

Search for term:

Pumice

Volcanology: pumice stone
Our tour guide Marta posing in Lipari's pumice...
Our tour guide Marta posing in Lipari's pumice...
Pumice from the Greek island Santorini
Pumice from the Greek island Santorini
Pumice is a very light, porous volcanic rock that forms during explosive eruptions. During the eruption, volcanic gases dissolved in the liquid portion of verz viscous magma expand very rapidly to create a foam or froth; the liquid part of the froth then quickly solidifies to glass around the gas bubbles. The volume of gas bubbles is usually so large that pumice is lighter than water and floats. Pumice is an important industrial mineral used to produce high-quality cement and lightweight, isolating building materials.
Pumice is a textural term for a volcanic rock that is a solidified frothy lava composed of highly microvesicular glass pyroclastic with very thin, translucent bubble walls of extrusive igneous rock. It is commonly, but not exclusively of silicic or felsic to intermediate in composition (e.g. rhyolitic, dacitic, andesite, pantellerite, phonolite, trachyte), but occurrences of basaltic and other compositions are known. Pumice is commonly pale in color, ranging from white, cream or grey, but can be green brown or black. It forms when gases exsolving from viscous magma nucleate bubbles which cannot readily decouple from the viscous magma prior to chilling to glass. Pumice is a common product of explosive eruptions (plinian and ignimbrite-forming) and commonly forms zones in upper parts of silicic lavas. Pumice has an average porosity of 90%, and initially floats on water.

Scoria differs from pumice in being denser, with larger vesicles and thicker vesicle walls; it sinks rapidly. The difference is the result of the lower viscosity of the magma that formed scoria. When larger amounts of gas are present, the result is a finer-grained variety of pumice known as pumicite. Pumice is considered a glass because it has no crystal structure. Pumice varies in density according to the thickness of the solid material between the bubbles; many samples float in water. After the explosion of Krakatoa, rafts of pumice drifted through the Pacific Ocean for up to 20 years, with tree trunks floating among them. In fact, pumice rafts disperse and support several marine species. In 1979, 1984 and 2006, underwater volcanic eruptions near Tonga created large pumice rafts, some as large as 30 km that floated hundreds of miles to Fiji.

Famous pumice deposits in Europe include Lipari Island (Italy), Santorini and Yali (Greece), as well as the Laacher See (Germany).

Related keywords (5):

explosive - obsidian - perlite - photoglossary.html - photoglossary.html
 

More on VolcanoDiscovery:

Copyrights: VolcanoDiscovery and other sources as noted.
Use of material: Text and images on this webpage are copyrighted. Further reproduction and use without authorization is not consented. If you need licensing rights for photographs, for example for publications and commercial use, please contact us.