Dump some basaltic rock into an induction furnace, heat it up to 2,400 degrees Fahrenheit, pour it into an insulated steel box about 18 inches tall, and inject it with high-powered jets of water and you’ve made yourself a backyard volcano. Except we don’t recommend it. Best to leave it to the geohazard experts, like , a research scientist at the University at Buffalo.
Sonder and his team of six researchers have been doing just this to understand what conditions cause the most violent eruptions in hopes of someday being able to conduct risk assessments for people living in volcanically active regions of the world. Their findings, recently in the Journal of Geophysical Research (JGR): Solid Earth, are the result of 12 experiments funded by the National Science Foundation.
While the findings are preliminary, the researchers concluded that spontaneous explosions were more likely to occur when water was forced at high pressures into a vertically oriented lava cavity. Eighteen-inch-high containers produced larger eruptions than eight-inch-high containers. Likewise, water traveling at 30 feet per second produced a more violent reaction than water traveling at six feet per second. The placement of the water injection also had an impact; the most impressive explosions resulted when there was about a foot of molten rock above the injection point.
In nature, a whole range of geologic reactions can result when molten rock and water meet. Events can either be deadly or subdued, depending on countless compositional variations and environmental conditions. When water is simply held by a hotter substance like lava, a layer of vapor forms around the water like the skin of a balloon, which lessens the transfer of heat into the water, effectively stabilizing it. Sometimes this water balloon will reach the surface and escape as steam and gas fumes.
When water is forced into a cavity of hot lava, however, it mixes in more quickly, destabilizing the vapor bubble that contains it. The water then heats up rapidly and expands in volume. Being three times lighter than lava, the water rises, disturbing the lava into an explosion. This sheds some light on the world’s most dangerous eruptions: Iceland’s Eyjafjallajökull erupted for two years straight, from 1821–1823, and its predecessor, Laki, killed a quarter of Iceland’s population in 1783. Hawaii's Kilauea eruption began in 1983 and lasted for 30 years, spreading lava flows for upward of 50 miles. What do these volcanoes have in common? They’re surrounded by water.
Most large-scale experiments have been done in service of industrial safety (e.g., metal production facilities and nuclear plants). Building on this research, scientists like Sonder and his colleagues have a long way to go before fully understanding the physics behind volcanic eruptions. Geohazard studies departments should get busy recruiting.