Around the world, 40 to 50 volcanoes are currently erupting or in states of unrest, putting hundreds of millions of people risk. Yet, reliable eruption forecasts have long eluded scientists, largely because they do not fully understand why magma starts or stops moving below the surface over weeks, months or years, before it finally erupts. The results of a new study may bring them one step closer.
The study finds that for the world’s most common type of volcano, it is the water content of magma that controls temporary storage depth; the more water, the greater the depth. The study challenges the prevailing theory that magma stops rising when its buoyancy equals that of surrounding rock. Deeper stalling might sound like good news, but that does not seem to reduce the chances of an eruption, scientists believe. And, water is the main driver behind explosive eruptions, so when something does finally let loose in a so-called “wet” magma, the results can be extremely violent.