Turrialba volcano (Costa Rica): activity updates and eruption news
Turrialba volcano (Costa Rica) update: explosions with ash plumes up to 3-4 km height
Friday May 20, 2016 16:24 PM | BY: T
Explosion of Turrialba today (OVSICORI-UNA webcam)
Same eruption closer view (image: RSA webcam)
Seismic activity during the past weeks, showing an increase since 17 May
Eruption yesterday with intra-crater pyroclastic flow
The activity at the volcano has increased during the past days and ash emissions from the active crater with intermittent stronger explosions have been near-continuous since yesterday.
First eruptive phase on 18 May (RSA)
A more violent phase of explosive activity began this morning at 07:29 local time, producing an ash column that rose about 3000 m above the crater to approx. 20,000 ft (6 km) altitude.
The most energetic phase lasted about 6 minutes and produced pyroclastic flows from collapsing parts of the ash column that affected the central crater and eastern rims.
An ash plume drifted eastwards and caused moderate to light ash falls in up to 60-70 km distance. A strong smell of sulfur was reported by eyewitnesses from various towns including San Rafael and San Francisco (50 km ENE).
Following similarly strong explosions yesterday afternoon (at 15:47, 16:09), the preventive exclusion zone was extended to a radius of 5 km around the crater. The school in the hamlet of La Central at the SW foot of the volcano remained closed.
After the strong explosion of 12 May, the volcano had been relatively calm for several days. In the evening of 17 May, seismic activity increased, first the number of long-period earthquakes and later volcanic tremor became stronger. Weak ash emissions started in the morning of 18 May, and became near-continuous after 11:04. Activity notably increased at 11:48 and a small explosion, which lasted 10 seconds and ejected ballistic blocks towards the crater rim, occurred at 12:56. This first new eruptive phase decreased at 14:30.
A second eruptive phase occurred yesterday morning at 07:27 and lasted approx. 6 minutes, generating pyroclastic flows that traveled to the central crater and the northern rim. Activity, at fluctuating levels, has been continuous since.
According to RSN, the current behavior of Turrialba is "entirely normal" for a volcano that is entering a new eruption. So far, monitoring data suggest that it involves a probably small batch of fresh magma that has risen to shallow depths (about 1 km) beneath the surface. The current explosions are likely the result of interaction of this magma (and its gasses) with the superficial hydrothermal system.
How the eruption will evolve is unknown, but two scenarios are considered most likely:
1. The activity continues at similar levels and evolves into a state where the conduit is open, allowing rapid degassing and rise of the new magma. This might translate in intermittent to continuous explosions of stronger size than now, producing ash columns up to about 5 km tall, such as were observed during the last historical eruption of the volcano in the 19th century.
This type of activity would likely only severely threaten areas up to 2 km away (ballistic ejecta, pyroclastic density currents). Ash fall is likely to affect mostly areas south and west of the volcano due to the prevailing northerly and easterly wind directions.
2. A second scenario is that the volcano's activity decreases, if the magma body is not large or gas-rich enough to reach the surface. Activity might gradually calm down and the volcano could fall back to dormant state.
Links / Sources:
Links / Sources:
- Informe de avance N°2 sobre la actividad sísmica y eruptiva del volcán Turrialba (Costa Rica): mayo de 2016 (RSN bulletin, pdf)
Monday, May 16, 2016
A new phase of ash emissions seems to be in progress at the volcano (which itself has been in clouds, preventing direct observations). ... [more]
Friday, May 13, 2016
A relatively strong explosion (the strongest so far in the ongoing series of intermittent eruptions) occurred yesterday morning at the volcano at 01:18 local time. The eruption only lasted a few minutes, but generating a shower of incandescent fragments and an ash plume that rose 3 km and drifted southeast across the Central Valley. ... [more]
Monday, May 09, 2016
After another series of ash emissions yesterday morning the volcano has been calmer today today and only produced a variable steam plume. ... [more]
Friday, May 06, 2016
The volcano remains at elevated unrest and had a new small eruption yesterday noon (at 12:05 local time), producing ash emissions similar to those during the past weekend. [more]
Wednesday, May 04, 2016
OVSICORI-UNA reported that at about 05:30 local time on 28 April seismicity at Turrialba increased, though gas-and-steam emissions continued at normal levels. ... [more]