Each volcano is unique. Even each eruption of the same volcano is unique. Until a volcano erupts, we cannot know what it will be like. The Kilauea volcano in Hawaii, one of the best-studied and most active volcanoes in the world characterized by effusive (low-explosive) dynamism, has had explosive eruptions in the past.
During this year, the Etna volcano, the most active volcano in Europe, has had numerous eruptions. Some of them have been characterized by fountains and lava flows, such as those that can be seen from Sunday on La Palma . And others, on the other hand, have caused large eruptive columns that reached more than a kilometer in height and forced the closure of the Catania airport, thus paralyzing air traffic to the island.
We cannot forget the 2010 eruption of the Eyjafjalla volcano in Iceland. The eruption began with a low-explosive eruption in March on one of the volcano’s slopes. However, when a new eruptive mouth opened just under the glacier in April, it turned into a more explosive eruption, spewing ash into the atmosphere that paralyzed northwestern Europe air traffic.
The past tells us about the future
Therefore, to know what type of eruption a volcano is going to have, the key is in the geological record. Geologists always say that “we must study the past to know the future”, and this fact is of vital importance in the study of volcanoes.
By studying the deposits of ancient eruptions we can know what types of eruptions have occurred in the past. For example, in a very general way and explained in a very simple way, we can relate lava flows with low explosive eruptions and pyroclastic flow deposits with explosive eruptions.
Pyroclastic flows are flows of gases and solid material that can reach 200 km / h and 900 ℃ in temperature. The main thing is to identify all these deposits in the field and then analyze them carefully in the laboratory to know their composition, origin, age, etc. and thus manage to understand how the volcano acted in the past.
Based on this work, forecasts can be made of what the next eruption will be like. That is why many times you hear something like “a low explosive eruption is expected”. That is, with the knowledge we have of the volcano, that would be the most likely eruption. However, we must bear in mind that although it is the most likely eruption, it is not the only one, and this should be expressed in all documents for volcanic risk management.
How will the eruption evolve on La Palma?
Focusing on the island of La Palma and what was known about the geology of the island, everything suggested that, if an eruption were to occur, it would be like the one that is occurring. In fact, if we see images of the last eruption of the island, that of the Teneguía volcano, and we compare it with the one that is happening, both eruptions are very similar (saving the distances, of course).
Now, the eruption could also have occurred in the sea, as it happened on the island of El Hierro.
In the case of having an underwater eruption, the associated hazards and eruptive dynamism would be slightly different. The greatest danger would come when the new volcanic edifice grew large enough to have a few meters of seawater above the crater. In that case, this would give rise to a type of explosive volcanism called Surtsey, in honor of the island of Surtsey (Iceland). A Surtseyan eruption is characterized by violent explosions and volcanic rooster tails, which are formed by a mixture of water vapor and volcanic ash.
Returning again to the island of La Palma, it is most likely that it will continue to have a similar behavior, but it is still too early to determine how it will act in the future and we must continue to monitor the island tirelessly.
Janire Prudencio So Señora, Professor of Volcanic Geophysics and Volcanic Risk, University of Granada
This article is republished from The Conversation under a Creative Commons license. Read the original article.
