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While some volcanoes are in remote locations, many are close to places where people have built cities and towns. Volcanic ash helps fertilize the soil, making for rich farmland. With many people living in close proximity to volcanoes, there is a tremendous potential for destruction of property and death as a result of an eruption. The immense scale and power of volcanoes means that predicting their behavior is our only defense against this kind of loss. We can’t prevent or stop volcanic events; we can only stay out of their way. But doing that isn’t always so simple.

Huge eruptions can move masses of soil and release amounts of energy that we can’t come close to matching. Compare our most potent hydrogen-bomb explosion, with the energy of 50 megatons of TNT, with Krakatau’s 5,250 megatons of TNT. In one sense, the Goliath size works to our advantage. Huge pools of magma don’t churn and rise and flow and give up their gases quietly. Volcanic bellyaching produces a cacophony of measurable changes—rumbles, shakes, and belches that serve as warning signs, as long as someone is reading them.

Volcanologists (scientists who study volcanoes) measure and assemble a mountain of data on the changes and look for telltale patterns. Then they interpret those patterns and decide: Is this volcano just tossing and turning during its slumber—in which case it will “roll over” and go back to sleep? Or is it about to wake with a bang and, if so, how soon?

Either outcome can happen, even with similar sets of data, since each volcanic system is unique and the science of forecasting is still emerging and evolving. Even so, today’s volcanologists have built an impressive tower of knowledge on the foundations laid by earlier observers. They’re constantly fine-tuning their ability to read and interpret the warning signs.

Photos courtesy of volunteer Seth Friedly. Volcanologists use many different types of equipment to measure changes in volcanoes, in hopes of learning to predict eruptions and save lives in nearby communities. Here, researchers set up to take measurements of Alaska’s Augustine volcano.