From the Document: "Volcanic eruptions are among Earth's most dramatic and powerful agents of change. Ash, mudflows, and lava flows can devastate communities near volcanoes and cause havoc in areas far downwind, downstream, and downslope. Even when a volcano is quiet, steep volcanic slopes can collapse to become landslides, and large rocks can be hurled by powerful steam blasts. Hazardous volcanic conditions might last for a day or decades, all the while threatening people's health and safety. Scientists with the U.S. Geological Survey and partner agencies assess hazards and closely monitor activity at the Nation's volcanoes. They provide volcano updates and warnings of hazardous situations, as well as guidance on actions to take. You can prepare your family and community by familiarizing yourself with the types of hazards at volcanoes near where you live and visit."
Fact Sheet 2018-3075
Geological Survey: http://usgs.gov/