There will be some indication that a volcano may erupt, but the time between the earliest indications of unrest and eruptive activity might be short, from days to weeks or months. The USGS Volcano Hazards Program (VHP) and its monitoring partners work to detect the earliest signals of volcanic unrest to forewarn communities at-risk and provide time for officials to activate emergency response plans and mitigation measures that can save lives and protect property. Because eruptions typically go through episodic cycles of increased activity and relative quiet after they begin, VHP scientists monitor volcanic behavior very closely to determine when it is safe to declare an eruption is over. In some cases, like in Hawaii, eruptions can continue for several tens of years.
Visit the site: https://volcanoes.usgs.gov/vhp/preparedness.html
There will be some indication that a volcano may erupt, but the time between the earliest indications of unrest and eruptive activity might be short, from days to weeks or months. The USGS Volcano Hazards Program (VHP) and its monitoring partners work to detect the earliest signals of volcanic unrest to forewarn communities at-risk and provide time for officials to activate emergency response plans and mitigation measures that can save lives and protect property. Because eruptions typically go through episodic cycles of increased activity and relative quiet after they begin, VHP scientists monitor volcanic behavior very closely to determine when it is safe to declare an eruption is over. In some cases, like in Hawaii, eruptions can continue for several tens of years.
Visit the site: https://volcanoes.usgs.gov/vhp/preparedness.html