Scientists have discovered the mechanism that helps pumice rocks to float for many years, as well as their phenomenon of sinking and re-floating.
Pumice is a mineral that can float on water. Scientists say that inside this rock there are many air bubbles , which help reduce their density and increase their buoyancy. However, the way the pumice blocks trap air, preventing leaks for many years has only been discovered, according to the International Business Times.
After X-raying the pumice stone, the scientists confirmed that the air bubbles inside were relatively large in size and connected to each other. If water gets into just one bubble, there’s nothing to stop it from seeping in and causing the rock to sink. Another mystery is that many pumice stones soak up the water and sink, but resurface not long after.
Submergence occurs because the air inside expands during warm weather.
The answer lies in the surface tension of the water inside the rock. This is also the factor that helps some small insects float on the water without sinking. Surface tension acts as a shell to prevent the water mass from deforming. The smaller the size, the more noticeable this effect is.
“A lot of the bubbles are tiny, like hairs stuck together. That makes the surface tension so powerful,” said researcher Kristen Fauria. Surface tension prevents water from entering the air bubbles. Subsidence occurs because the air inside expands during warm weather.
This research may reveal how giant pumice blocks form. Some of the pumice rocks are up to 1m in diameter, while normally they are only as big as an apple. Pumice forms when volcanoes erupt on land or under water. When molten lava meets water, it freezes quickly, leaving many air bubbles inside.
Pumice floating on water after a volcanic eruption.