Predicting topographic collapse following lava dome growth at Ibu volcano (North Maluku, Indonesia) using high-resolution PlanetScope images

In this study, we described a rare case of lava dome growth at Mt. Ibu in West Halmahera Regency, North Maluku Province, Indonesia, in which the inner crater was filled, even exceeding the outer crater rim on the northern flank. The observed lava dome growth caused concern due to the rapid volumetric change, followed by topographic collapse, thus producing hazardous pyroclastic flows and debris avalanches. Based on the condition of Mt. Ibu, we calculated the lava dome area and volume using PlanetScope images and a national digital elevation model, respectively. Comparing the lava dome volume to the crater space, we predicted the area and time of future topographic collapse. We calculated the time series of the lava dome volume from January 2020 to August 2022 to predict the time of the maximum volume of the outer crater rim using autoregressive integrated moving average (ARIMA) and seasonal autoregressive integrated moving average (SARIMA) models. According to the time series, Mt. Ibu was beyond the critical conditions for collapse when the lava dome exceeded the outer crater rim by approximately 0.114 km3 or an area of 1.477 km2. Then, ARIMA and SARIMA predictions were simultaneously obtained, and the critical condition was predicted to be achieved in 2037. The confidence level of the ARIMA model was captured by the root mean squared error (0.008 km2) and mean absolute percentage error (approximately 0.554%). Moreover, the values were approximately 0.009 km2 and 0.397%, respectively, for the SARIMA model.