No Signs of Imminent Eruption on Tenerife, Says Volcanologist
Following almost three weeks of very weak seismic activity, volcanologist and researcher Pablo J. González from the IPNA, who represents the CSIC on the Pevolca Scientific Committee, insists there is no evidence of a magmatic intrusion on the island. He therefore rules out the possibility of an eruption in the short or medium term. For that to happen, he stresses, more indicators would need to coincide: greater seismicity, significant ground deformation in a short period, and a change in gas emissions. None of this has occurred so far.
Understanding the Current Seismic Swarms
The tremors are small, low-magnitude movements located at the base of the Earth’s crust. Such seismic swarms are typical of volcanically active areas like Tenerife. At present, there are no associated signals of ground deformation or changes in gas emissions. The situation being monitored is part of routine surveillance. Consequently, as of today, there are no implications pointing towards an evolution into an eruptive process; more factors would need to come into play.
Anomalous but Not Unprecedented
The swarms are anomalous for the instrumental monitoring period of Tenerife’s surveillance networks, mainly because they are occurring in a short timeframe and are concentrated in a specific zone. However, they are not at all rare for volcanic islands in general. Recently, the island of Terceira in the Azores has experienced several similar episodes. Tenerife itself had a comparable episode between 2004 and 2006 which did not evolve into an eruptive process.
“I was just beginning my doctoral thesis at the time and I remember the 2004 event well, which lasted until 2006,” said González. “That was seismicity of a higher magnitude and coincided with an increase in carbon dioxide (CO2) emissions, more intense fumarolic activity, and even clear anomalies in microgravity. Those were much clearer signals than the current ones, indicating that Tenerife’s deep magmatic and hydrothermal system had reactivated. Right now, we do not see all those indicators showing anomalous values.”
Vigilance and Communication Continue
Of course, these small earthquakes must be tracked, which is why available scientific and technical information is being gathered and experts are meeting to advise authorities and inform the public as effectively as possible. However, it is important to remember that for now, it is only the persistence and repetition of micro-earthquakes that recalls 2004.
In most volcanoes, micro-seismicity without other changes typically indicates internal adjustments (micro-fracturing) of the subsoil and/or the circulation of fluids. By itself, this signal does not imply an eruptive process. It is a very important parameter, but not the only one. This is why volcanic surveillance monitors many parameters, such as gases, ground deformation, and fumarole temperatures.
The Signs That Would Signal Real Danger
To speak of a volcanic eruption danger, we would need to see more simultaneous signals. These include clear, rapid, and sustained ground deformation (for example, several centimetres in a few days or weeks), rapid changes in carbon dioxide and sulphur emissions, earthquakes felt by the population, a lateral or upward migration of seismicity towards the surface, and variations in ground temperature and/or in the Teide’s fumaroles. Almost none of this is happening now.
“The logical course is to continue monitoring, add more instrumentation if possible, and maintain communication with the public,” González stated.
No Measurable Deformation Detected
Ground deformation is a parameter González’s group follows in great detail, as they are experts in its interpretation. But for the moment, they see no appreciable deformation in the GPS networks or InSAR data (a satellite imaging technique). Associated with February’s micro-seismicity, no appreciable and/or measurable changes have occurred.
The available data indicate that if there is deep magma movement, it is not having measurable effects on the surface or showing typical signs of intrusion. As expected, González concurs with the consensus reports from the Pevolca scientific committee in which the CSIC participates. The most likely explanation is that the tremors are due to the circulation or ascent of hot fluids of magmatic origin up to the intrusive complex located at the base of the oceanic crust, at around 10 kilometres depth.
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