5:15 PM - 6:45 PM
[SVC29-P04] Recent activity of diffuse soil carbon dioxide gas at Izu-Oshima volcano
Keywords:Izu-Oshima, Diffuse soil gas, Carbon dioxide gas, Emission rate
Since the dissolved rate of carbon dioxide in the melt decreases even at a relatively small vesicularity (Giggenbach, 1996), it is expected that increasing magmatic activity can be detected early by detecting the increase of diffuse carbon dioxide gas. For example, a year before the eruption of the 2000 Usu volcano eruption, an increase in diffuse soil carbon dioxide was confirmed (Hernández et al., 2001).
In order to monitor magma activity at Izu-Oshima volcano, we have conducted diffuse gas emission observations ten times from 2017 to 2024. The device used was the portable diffuse flux meter manufactured by WEST System that uses a LI-COR CO2 detector. We have surveyed mainly within the summit crater of Mt. Miharayama, and this mapping observation showed that the amount of CO2 emission over the past seven years has remained within 30 tons/day, with no major fluctuations (Fig 1, Fig 2(a)). This estimated emission rate of 30 tons/day is approximately 10% of the emission rate before the 2000 Usu volcano eruption.
Since 2022, around 20 fixed points have been arranged and repeated observations have continued. It has been pointed out that observation data of soil diffuse gas includes the influence of the environment such as weather (Morita et al., 2019). In this fixed-point observation, we conduct observations that take into account the effects of weather and soil moisture, and also take measures such as averaging multiple observations at the same point and taking measures to prevent leaks from the observation chamber. These improved the quality of observation data. As a result, the temporal changes at fixed points generally showed the similar tendency to those of the mapping observation (Fig 2(b)).
In order to monitor magma activity at Izu-Oshima volcano, we have conducted diffuse gas emission observations ten times from 2017 to 2024. The device used was the portable diffuse flux meter manufactured by WEST System that uses a LI-COR CO2 detector. We have surveyed mainly within the summit crater of Mt. Miharayama, and this mapping observation showed that the amount of CO2 emission over the past seven years has remained within 30 tons/day, with no major fluctuations (Fig 1, Fig 2(a)). This estimated emission rate of 30 tons/day is approximately 10% of the emission rate before the 2000 Usu volcano eruption.
Since 2022, around 20 fixed points have been arranged and repeated observations have continued. It has been pointed out that observation data of soil diffuse gas includes the influence of the environment such as weather (Morita et al., 2019). In this fixed-point observation, we conduct observations that take into account the effects of weather and soil moisture, and also take measures such as averaging multiple observations at the same point and taking measures to prevent leaks from the observation chamber. These improved the quality of observation data. As a result, the temporal changes at fixed points generally showed the similar tendency to those of the mapping observation (Fig 2(b)).