When lava and water come into contact, you usually have to prepare for an explosion. Or not. Researchers at the University of Buffalo wanted to explore the circumstances that bring these two elements together to create gigantic bubbles of liquid rock. For this, they produced their own lava in a laboratory and blew it up.
Recipe for a beautiful explosion
Sauté 38 kg of molten rock in a crucible. Add water. Here is in essence the recipe used by the researchers during their experiment, to study the still unknown interaction that occurs between lava and water. In a previous study, a German team had ‘poked’ the lava with water to trigger an explosion, an observation to which researchers brought their own conclusions.
A total of 12 tests were conducted, with a water injection rate ranging from almost 6.5 to 30 feet per second, during which the lava was contained in thermally insulated metal boxes, which were 8 to 18 inches high. The observations made it possible to note that the reactions were most spectacular when the water hit more quickly and the lava was contained in the highest receptacles.
From vaporisation to eruption
When water is rapidly injected into a high lava column, it mixes with it. This causes a destabilisation of the vapour film that would usually protect the water (a phenomenon that is observed with the Leidenfrost effect). The water, in direct contact with the lava, quickly vaporises and takes up more and more space. The result? An explosion takes place. Injected at a lower speed, the water usually manages to maintain its protective vapour film or evaporates even before piercing the surface of the lava.
‘This study is in its infancy, so we still have many years of work before us to be able to consider a set of factors and combinations that influence what happens when the lava or magma meet the water,’ says Greg Valentine, co-author of the study, published in the Journal of Geophysical Research: Solid Earth. ‘Understanding the basic processes related to volcanoes will help us better predict the course of future eruptions.’