Rebecca Salvage is a third year PhD student in the School of Earth and Environment, University of Leeds. She is currently in Ecuador collaborating with IG-EPN. Today she writes about her first hand experience of the ongoing eruption of Tungurahua volcano.
I came to Quito at the end of January to work with the IG-EPN (Instituto Geofisico) on seismic signals at volcanoes, and in particular at Cotopaxi which has a wealth of data. Little was I expecting to be caught up in a volcanic crisis which has seen people evacuated from their homes, large pyroclastic flows and huge ash columns.
Tungurahua is an active stratovolcano located in the Northern Volcanic Zone in the Cordillera Oriental in Ecuador. It’s not as though this volcano is always quiet, explosion signals and ash plumes were last seen here in November 2013. However, the events which started on the 30th January and are still continuing at the time of writing (6th February) are considered to be “anomalous” due to the threat to the population in the area and due to the strength of the activity (header image).
Fig 1. Eruption of Tungurahua – 30th January 2014 – ~3pm (local time). Plume height approx. 2km.
Small explosions, accompanied by over 100 seismic signals which included low frequency seismicity believed to be an indicator of fluid movement within the conduit, began on the morning of the 30th January 2014. Small ash plumes could be observed at heights of 2km above the volcano, which continued throughout the day at regular intervals (fig. 1). At this time, I was downloading data and fixing a seismic station approx. 11 km from the vent, but the ash was already noticeable in your hair, on your clothing and skin. Several explosions occurred during the time when we had a clear view of the volcano from the site, where we were based for several hours. Trying to keep the solar panels and the camera free from ash and dust was a continuous battle, since all of the images and seismicity was being transmitted directly back to OVT (the local observatory for Tungurahua which is officially run by IG-EPN in Quito).
Overnight between January 30th and January 31st, explosion events continued with associated seismic activity. It was also possible to see the upper parts of the volcano lit up by incandesce during the night as hot material was erupted from the vent, giving a “glowing” nature to the volcano. Following this, activity significantly declined for most of the day of the 31st (a worrying fact since it was thought that the volcano might contain a plug under which a lot of pressure was building) until at 17h01 a moderate explosion occurred which sent an ash column up to 2km high and winds directed the ash in both a SW and SE direction. Unfortunately, from our position at another seismic station on the flanks of Tungurahua (5.5 km from vent) the entire volcano was covered in cloud, although we convinced ourselves at some points that we could see ash in the clouds. The seismic station and solar panels were covered in approx. 2mm of ash from the activity over the past few days (Fig.2), which is a significant amount at this distance and direction.
Fig 2. Hugo Ortiz (IG-EPN Volcano Seismologist) wiping ash (~2mm) off solar panels.
Again, overnight there was very little activity at the volcano (a seismic silence), until around 08h00 on the 1st February when a seismic swarm was detected at shallow depths beneath the crater. At this time, the observatory reported to the authorities and the citizens of the area that an eruption was thought to be imminent, and that they were not ruling out the possibility of a pyroclastic flow. They were not wrong – at 17h12, 17h22 and 17h39 on the 1st February large explosions occurred at Tungurahua, generating ash columns as high as 8km, with continuous release of gas and ash particles. Ash fall was mainly directed to the SE.
Following these explosion events and the continuous degassing and ash emissions, several pyroclastic flows were generated which flowed in a NW, NE, W and SW direction, reaching up to 8km in distance from the volcanic vent. From the video (link) it is clearly seen that the ash column collapsed to generate the pyroclastic flow being filmed, which has devastated parts of the volcanic flanks. Thankfully, no reports of pyroclastic flows reaching roads or destroying bridges have been made, and as of yet there has been no loss of life. From around 18h32, another phase of Strombolian activity occurred with continuous gas emissions and explosion events. From 19h00 the eruption became purely explosive, with explosive events occurring regularly almost every minute, creating pressure waves which led to the vibration of buildings and windows in the areas close to the volcano. Following this, the activity declined and explosions became more sporadic in nature.
Fig 3. Example drumplot from Tungurahua from the 3rd February 2014 showing seismicity. Clearly shown are the explosion signals.
February 2nd saw 3 minor explosions at 06h59, 07h23 and 08h01 which saw the emission of ash clouds. Overnight and into February 3rd, a number of larger explosions were seen (Fig.3), with ash plumes reaching up to 4km. A wind from the South drove ash Northwards and in the late afternoon there were reports of ash fallout in the Southern parts of Quito. The city was certainly hazy, and continues to be. Even in the centre of Quito, members of IG-EPN reported ash on their cars as they left the institute in the evening.
Fig 4. Drumplot from Tungurahua on the 4th February.
Since the 4th February Tungurahua remains seismically active (Fig. 4) with some smaller explosion signals observed. No pyroclastic flows have been reported since February 1st, although the Institute, authorities and population remain in a state of alert.
–
All information from personal experience and those at IG-EPN. PHOTO CREDITS: REBECCA SALVAGE
CLIMATE AND GEOHAZARDS 