While still vacationing in Karpathos, Greece, I frequently visit and swim at the beaches. There are many beautiful things to be found on these beaches, one of them being the geological landscape. The rock formations throughout the years have built incredible cliffs and caves. There are also several beaches in which seashells are embedded into rock. In addition to these special rock formations, another interesting geological find common to Greek beaches is pumice. During each one of my visits to Greece, I have managed to find this light-colored, porous rock at the beach. But exactly how is it made and where does it come from?
Although pumice is found in Greece, it is also found in other countries such as Italy, Spain, Turkey, as well as the United States. There are two forms of pumice: rock pumice (which I found on the beaches) and pumicite (finely grained pumice). Within these rocks are many oxides, mainly silicon dioxide, some aluminum oxide, and trace amounts of other oxides. The pumice in Greece is rhyolite pumice, which is white-grey in color. Trachyte pumice is also found in this color. Another type of pumice, referred to as andesite pumice is either yellow or brown in color. Finally, pumiceous basalts (found on the islands of Hawaii) are black.
Pumice is created as a product of volcanic eruptions. Volcanic magma contains dissolved gases that are under a significant amount of pressure. During volcanic eruptions, this pressure is released, and causes the gases inside to escape. The vesicles found throughout this rock are the product of these escaped gases. While being released into the air, foam is created. It is no wonder how the word pumice comes from the Latin word, pumex, meaning foam. This foam is cooled quickly as it passes through the air, therefore the atoms of the rock do not have enough time to organize themselves into a crystalline structure. The pumice is fully solidified by the time it falls to the ground.
Due to these vesicles present and the thin walls between them, pumice has a low specific gravity of 0.64. This specific gravity is lower than that of pure water (1.00) and sea water (1.03), causing it to float on water. Volcanic eruptions that occur on islands or below water can cause pumice to float on the surface of water and be driven around by winds. Large amounts of pumice that are found floating in the ocean are called “pumice rafts” and can be a risk to boats around them. However, pumice that floats on water can eventually become saturated and sink.
Pumice has many uses, from construction to foot care. Its biggest use in the United States is in the creation of light concrete blocks. In horticulture, pumice is used to oxygenate soil and improve its moisture, as well to grow plants hydroponically. Due to it being neither toxic nor hazardous, pumice has been used in the paint and plastics industry as a filler. Pumice also has other applications and is used in stone washing jeans, as well as the production of “Lava Soap”, skin exfoliators, and many other products.
With Greece’s ongoing financial crises and the referendum occurring this past week, there has been much debate surrounding the country. However, the best way to help those in Greece is to book a holiday there. Once you are in Greece, you can see the beauty of the beaches, as well as the exquisite complexity of its geological landscape.