Forecasting volcanic activity relies fundamentally on tracking magma pressure through the use of proxies, such as ground surface deformation and earthquake rates. Lava lakes at open-vent basaltic volcanoes provide a window into the uppermost magma system for gauging reservoir pressure changes more directly. At Kilauea Volcano (Hawai'i, USA) the surface height of the summit lava lake in Halema'uma'u Crater fluctuates with surface deformation over short (hours to days) and long (weeks to months) time scales. This correlation implies that the lake behaves as a simple piezometer of the subsurface magma reservoir. Changes in lava level and summit deformation scale with (and shortly precede) changes in eruption rate from Kilauea's East Rift Zone, indicating that summit lava level can be used for short-term forecasting of rift zone activity and associated hazards at Kilauea.
Patrick, M. R., Anderson, K. R., Poland, M. P., Orr, T. R., & Swanson, D. A. (2015). Lava lake level as a gauge of magma reservoir pressure and eruptive hazard. Geology, 43(9), 831–834. https://doi.org/10.1130/G36896.1