How do you monitor a dangerous volcano that’s too far out in the boonies to wire with GPS and seismometers or watch close up with a webcam?
You do the best you can.
Cleveland Volcano is way out in the middle of Alaska’s Aleutian Island volcanic arc, and it’s dangerous because nearby Anchorage is a major hub for aircraft following the great-circle routes between North America/Europe and Asia.
As many people know, ash and jet engines don’t mix. When Redoubt Volcano, much closer to Anchorage, erupted in 1989-1990 (VEI 3), five commercial jets were damaged from ash encounters, and flight disruptions cost Anchorage’s airport over $2.5 million (source, PDF file).
Cleveland is also the only Aleutian volcano to kill somebody recently. During its VEI 3 eruption in 1944, per the Smithsonian’s Global Volcanism Program, a US soldier stationed on the island died, probably in a mudslide.
Still, on a quiet day, it is a wild, beautiful place.