Deferred by the news of Krakatau and Etna, return to the balance sheets of the year by the observatories:
In 2018, the Volcanic Monitoring Program developed several tools to improve the communication of the results of the continuous monitoring of volcanoes, including a scale of activity level, weekly and daily bulletins, and webcam views. seismic activity and gas geochemistry on the OVSICORI-UNA website: http://www.ovsicori.una.ac.cr/.
Volcanic monitoring is done from a network of different devices.
More specifically for active volcanoes in 2018:
The Turrialba is in activity level in 2018: 3 (erupting volcano) with an open system activity, generating frequent passive emissions of ash due to the slow but almost constant increase of a small magmatic volume.
On the 336 days of the year until December 20, the volcano emitted ashes for 194 days, more than 58% of the days of this year. At the beginning of the year and in August-September 2018, 2 inflation periods were detected that could be associated with a magmatic intrusion of 15 to 20 million cubic meters, at a depth of 10 to 15 km below the sealevel, located 3 km southeast of Irazú crater. These intrusions could be at the origin of the increase of eruptive activity on the volcano between February and March, as well as from May to October 2018.
Some explosions generated by these impulses were large enough to trigger a ballistic activity greater than 400 m around the crater.
Since the end of October, the magmatic activity has decreased but not the ash emissions. The hydrothermal system is considered to be formed again by generating explosive magma-water interactions and fragmentation of the magma in the column as the origin of ash emissions.
The Poas volcano is in activity level in 2018: 2 - 3 (active volcano - erupting)
It showed low activity, dominated by hydrothermal processes and degassing. Several periods of sustained activity have been recorded in the form of "borbollones".
In general, the flow of gas has significantly decreased compared to 2017 and the hydrothermal system has begun to reform, as evidenced by the recovery of the lake since January. This lake disappeared during the dry season (March-May) and reappeared later, generating variability in the monitored signals (seismicity, flow and gas ratios). The deformation recorded a slight deflation from June. No magmatic intrusion was detected.
The color of the lake changed from gray to green at the end of the year, which is generally associated with less intense convection activity in the lake despite the active maintenance of underwater fumaroles. And in mid-December 2018, eruptive activity increased, with hydrothermal eruptions with steam columns on December 19 and 20, and the near-disappearance of crater lake.
A change in the seismic model appeared on October 8 with many high amplitude LPs and short duration tremors, with no superficial manifestations.
The Rincon de la Vieja volcano has maintained an intense activity with frequent phreatic eruptions, but of a smaller amplitude than in 2017. A modification of the deformation model towards the extension was observed in October.
In 2018, volcanic activity associated with Irazú volcano remained very low. Some seismic swarms were recorded around May 20th. A permanent multi-gas station has been installed to detect the first signs of a possible magma intrusion. At present, no magmatic activity related to the Irazú volcano is detected.
Irazu - photo 12.12.2018 / MSc. Elena Badilla Coto, profesor of Escuela Centroamericana de Geología UCR.
The activity level of the Arenal in 2018: 0 (asleep) with potentially associated risks of earthquakes and landslides.
The deformation associated with the stabilization of the flanks of the volcanic building has decreased this year 2018. Some isolated LP earthquakes have been recorded that do not represent a new activity in the volcano. DOAS transects indicate that there is no SO2 emission. No magmatic activity was detected.
Source: Ovsicori - UNA & Red Sismologica Nacional