How are Volcanoes monitored?

-Seismometers. Earthquakes can trigger Volcanoes -Tiltmeters and GPS. Volcanoes tend to swell nearer its eruption -Overseeing Gases on a Volcano. Increase in Sulphur Dioxide means an eruption is nearer -Temperatures. Volcanoes become much hotter when magma rises in the Main Vent -Timeline. Patterns.