Predicting volcanic eruptions is one of the main concerns of volcanology. When a volcano erupts, little can be done to prevent property damage in surrounding area. But many lives can be saved if people in the area are evacuated before the eruption begins.
Most volcanic eruptions cannot be predicted. However, some volcanoes, such as the ones in Hawaii, has a built-in warning system. Before the volcano erupts, it expands slightly as magma rises, many small earthquakes occur. The temperature in the surrounding area also increases, and clouds of gas start to pour from the vent.
Scientists use several devices to predict when such a volcano will erupt. They use an instrument called a tiltmeter to measure the expansion of a volcano. A device called a sismograph helps detect earthquakes. Thermometers check temperature increases in the area, and gas detectors measure the amount of gas.
