Volcano deformation has been measured at Campi Flegrei throughout its geological history, over varying timescales, alternating between uplift and subsidence phases. Geodetic measurements of ground elevation are available since 1905 and indicate episodes of ground uplift in 1953, 1969, and 1982, totalling approximately 4 m of vertical displacement (Del Gaudio et al., 2010).
Significant episodes include the 1982-1984 of unrest, where up to 1.8 m vertical uplift occurred in the caldera at Pozzuoli. A slow deflation phase began in 1985, interrupted by minor uplift episodes of few cms, seismic swarms and degassing episodes in 1989, 2000, and 2004–2006.
Between 2005-2011, Campi Flegrei has been uplifting, at a rate of 1 cm/yr. In 2011, the rate of uplift increased, reaching 9 cm/yr in 2012 in Pozzuoli, as registered by the Neapolitan Volcanoes Continuous GPS (NeVoCGPS) network operating in the Neapolitan volcanic districts.
Episodic pulsed inflations of the caldera floor have led to gas injections into the hydrothermal system, accompanied by seismic swarms shallower than 2–3 km depth.