Total mass estimate of the January 23, 2018, phreatic eruption of Kusatsu-Shirane Volcano, central Japan

On January 23, 2018, a small phreatic eruption (VEI = 1) occurred at the Motoshirane Pyroclastic Cone Group in the southern part of Kusatsu-Shirane Volcano in central Japan. The eruption ejected ash, lapillus, and volcanic blocks from three newly opened craters: the main crater (MC), west crater (WC), and south crater (SC). Volcanic blocks were deposited up to 0.5 km from each crater. In contrast, the ash released during this eruption fell up to 25 km ENE of the volcano. The total mass of the fall deposit generated by the eruption was estimated using two methods, yielding total masses of 3.4 × 104 t (segment integration method) and 2.4 × 104 t (Weibull fitting method). The calculations indicate that approximately 70% of the fall deposit was located within 0.5 km of the craters, which was mainly attributed to the low height of the eruption plume.

Air-Fall Ash from the Main Crater of Asama Volcano on August 7, 2019, and its Water-Soluble Components

We collected volcanic ash immediately following the eruption of Mt. Asama on August 7, 2019, observed the characteristics of ash particles, and analyzed the water-soluble components. The volcanic ash consisted mostly of altered fragments, and no clear evidence of essential materials was found. The volcanic ash contained large amounts of water-soluble components, Cl and SO4 at concentrations of 8,710 mg/kg and 49,100 mg/kg, respectively. These results indicate that this eruption was caused by the phreatic explosion and that part of the volcanic edifice of Mt. Asama was fractured and emitted.

Cyclic Behavior Associated with the Degassing Process at the Shallow Submarine Volcano Tagoro, Canary Islands, Spain

Tagoro, the most recently discovered shallow submarine volcano on the Canary Islands archipelago, Spain, has been studied from the beginning of its eruptive phase in October 2011 until November 2018. In March 2012, it became an active hydrothermal system involving a release of heat and gases that produce significant physical–chemical anomalies in the surrounding waters close to the seabed. Fast Fourier transform (FFT) and wavelet time-domain-frequency analysis techniques applied to filtered time series of temperature, salinity, pressure, pH, and oxidation-reduction potential (ORP) data from a conductivity-temperature-depth (CTD) device mounted on a mooring and deployed at the deepest part of the main crater at a depth of 127 m, have been used to better understand the dynamic processes of the emissions during Tagoro’s degasification phase. Our results highlight that the hydrothermal system exhibited a stationary cyclic degassing behavior with a strong peak of a 140-min period centered on a significant interval of 130–170 min at 99.9% confidence. Moreover, important physical–chemical anomalies are still present in the interior of the main crater, such as: (i) thermal increase of +2.55 °C, (ii) salinity decrease of −1.02, (iii) density decrease of −1.43 (kg∙m−3), and (iv) pH decrease of −1.25 units. This confirms that, five years after its origin, the submarine volcano Tagoro is still actively in a degassing phase.

Predicting the probability of Mount Merapi eruption using Bayesian Event Tree_Eruption Forecasting

Mount Merapi is one of the active volcanoes in Indonesia that had varied eruption periods from two to eight years. Due to the density of the population living around the slopes of Mount Merapi, its eruptions caused high number of victims. In order to avoid high number of victims, the disaster management should be improved. Disaster management consist of four phases i.e. mitigation, preparedness, response and reconstruction. In disaster mitigation phase, prediction of the Merapi unrest probability is needed. This paper focus on how to predict the probability of Merapi unrest based on volcano-logical information by using Bayesian Event Tree. Bayesian Event Tree (BET) is a probabilistic model that merges all kinds of volcano-logical information to obtain probability of any relevant volcanic event. The result showed that the probability of Merapi unrest is 0,822. In the next eruption, it has predicted that the volcanic explosivity index (VEI) 2 was biggest chance with the probability of 0,549. It showed that the eruption will take place in the main crater of Merapi with the probability of 0,938.