On June 17, Mount Lewotobi Laki Laki in Indonesia erupted, spewing hot ash, which prompted local authorities to raise the alert level to the highest possible. So far, no casualties have been reported, but residents were asked to stay vigilant.
According to Indonesia’s Geological Agency, the volcano released 10,000 meters (32,800 feet) of thick gray clouds into the air. The explosion of ash later formed into a mushroom-shaped cloud that could be observed from as far as 90-150 kilometers (56-93 miles) away.
Indeed, we've seen some monstrous eruptions of volcanoes throughout history. Most of these volcanoes are stratovolcanoes, meaning cone-shaped elevations that were built over time from layers of ash and lava. Due to their relatively soft composition, pressure builds up inside until they blow up, which results in sudden explosive eruptions. Their steep slopes then generate pyroclastic flows, making them some of the most dangerous types of volcanoes.
The power of such eruptions is measured using the Volcanic Explosivity Index (VEI), which is a scale that goes from one to eight. Each succeeding VEI is 10 times greater than the last.
Need examples? Click on for some of the worst volcanic eruptions in history.