In 2018 Kilauea volcano erupted a decade’s worth of basalt, given estimated magma supply rates, triggering caldera collapse. Yet, less than 2.5 years later Kilauea erupted again. At the 2018 eruption onset, the pressure within the shallow summit reservoir was ~20 MPa above magmastatic as implied by the elevation of the primary vent. By the onset of collapse this decreased by ~ 17 MPa \citep{anderson2019}. Analysis of magma surges observed following collapse events implies that excess pressure at the eruption end was only ~ 1MPa. Given the elevation difference between the 2018 and 2020 vents, we estimate ~ 11.5 MPa pressure increase was required to bring magma to the surface in December 2020. Analysis of GPS data between 8/2018 and 12/2020 shows there were even odds this condition was met
9 months before the 2020 eruption, and 73% probability on the day of the eruption.