Active volcanoes are sprinkled around the world. In the US, Hawaii, Alaska and the Northwest are the only places that have active volcanoes. Active volcanoes erupt regularly and lava that is spewed moves slowly. While getting out of harms way is easy, there is no way to stop a lava flow. It destroys anything in its path. Eruptions are powerful events and oftentimes accompanied by earthquakes, landslides, acid rain, fire etc. Particularly dangerous are sideways eruptions. They can hurl boulders (weighing tons) several miles. Direct hits are catastrophic.
Volcanic ash spewed by an eruption is toxic and can cause serious damage when inhaled. The old and the very young are particularly vulnerable. Emergency response officials try to maintain a 20 mile perimeter when an eruption occurs. Unfortunately, in several countries, people live in the shadow of active volcanoes. Loss of life is proportional.