Pumice

We found pumice at Lagoa Azul! I'm still limited today, so I'll take my time to write something about pumice.

It was dancing on the surface of a small stream near a small weir, circling around, obviously waiting for us to collect some, which we did.

Pumice is widespread in the Azores due to the intense volcanism, especially on São Miguel and Faial. The light-colored, porous rock shapes the landscape, forms beaches at Lagoa do Fogo, and is used locally as a building material (tuff).

Pumice is a very light, highly porous volcanic glass that forms during gas-rich eruptions and floats on water due to its low density.

It forms when gas-rich lava cools rapidly and is often white, gray, or brown in color. During its formation, viscous lava is foamed up by water vapor and carbon dioxide.

Chemically, pumice is no different from other lava (its chemical composition can vary just as much as that of lava), but it is significantly lighter (approximately one-third the density) and, due to pores caused by volcanic gases, often has a much lighter color than lava rock of the same composition.

Pumice can reach the sea through relatively steady land erosion, but also through acute volcanic eruptions. The particularly large eruption of Mount Tambora in Indonesia in 1815 ejected so much pumice into the sea that ships were still encountering floating pumice rafts years later.

In August 2012, light-colored pumice was sighted floating in the South Pacific Ocean between New Zealand and Tonga, covering an area of ​​463 × 55 km. It is attributed to the underwater volcano Monowai.

In August 2019, catamaran sailors Michael Hoult and Larissa Brill discovered a pumice carpet covering 150 km² and collected samples of the 1–25 cm diameter stones. NASA satellite images show that an underwater volcano had erupted off the island nation of Tonga on August 7th.

Carpets of this type occur in this region approximately every 5 years.Read more