Volcanoes go silent before an eruption
Researchers from Carnegie Institution of Science have been monitoring the seismic activity of more than 50 volcanic explosions in active volcanoes since 2009. Leading up to an eruption, volcanoes threw out plenty of smoke, fire, and sputtering ground movement, as expected. But, in the moments right before an eruption, the volcanoes went suddenly and completely quiet and still.
Most eruptions had quiet periods of less than 30 minutes, and some had lulls lasting only a few minutes. The longest one measured 10 hours, but then it was also followed by the largest eruption that researchers had seen. When researchers noticed that the longest lull was also linked to the biggest explosion, they compared all explosion sizes to the length of the quiet periods and found a clear correlation — the shorter the lull, the smaller the explosion; the longer the lull, the bigger the explosion.
Researchers can use these long, ominous silences to predict how big of an explosion will occur, right before it happens.