Can reality far surpass the wildest imagination? In many cases yes, and the history of Mount Saint Helens can only confirm it.
It is the morning of May 18, 1980, an apparently calm spring morning like many others, but not for the State of Washington, in the USA: here, at 8:32, a very violent explosion obliterates the entire side of a volcano, the Mount Saint Helens, among the most active in the entire North American continent.
An eruption that will go down in history, marking a fundamental watershed in modern volcanology and becoming a real legend that has fascinated generations of volcanologists (and not only).
Behind this spectacular eruption, one of those which Kant would have drawn to illustrate his concept of "sublime", the incredible stories of a group of young American volcanologists intertwined, so enthusiastic about their work that their destiny was inextricably linked to that of the mountain.
We interviewed Tullio Ricci, INGV volcanologist and a great fan of Mount Saint Helens, to accompany us on this adventurous journey to discover an eruption that seems to have come from the pen of a novelist but which, instead, has really changed history forever of volcanology.
Tullio, why is that of Mount Saint Helens on May 18, 1980 remembered as the eruption that changed the history of volcanology?
For several reasons, all related to each other. First, the eruption of Saint Helens was the first major explosive eruption that modern volcanologists have witnessed. This event required a multidisciplinary monitoring and integration effort probably never observed before, laying the foundations for current volcanology in which data from geophysics, geochemistry, geodesy, geology and hazard studies are closely interconnected and interpreted jointly. Saint Helens has been a laboratory for the study of precursors, explosive eruptive dynamics and for the interpretation of morphologies present in other volcanic areas, such as those deriving from slope collapses.
Furthermore, it must be considered that before the 1980 eruption, Saint Helens did not have its own monitoring network, although it was already recognized as the most active volcano in the Cascade Range, the Cascade Range, in the northwestern United States. The closest seismic station was located a few tens of kilometers away from the volcano.
The 1980 eruption was preceded by a phase of unrest, of agitation, characterized by seismic activity and by the swelling of the north side of the mountain: a sign that magma was accumulating below the surface. All of these signals brought the USGS (the "cousin" of INGV) to implement the surveillance system of the volcano, both during the pre-eruptive phase and immediately after the eruption.
However, at the time, our American colleagues had almost exclusively experience of effusive volcanoes, the classic Hawaiian volcanoes with low viscosity lava flows, almost "tourist" to observe. Imagine what it must have been like to deal with a volcano whose northern flank was swelling at a rate of 2 meters a day and the subsequent explosion that devastated some 600 square kilometers of surrounding forests and lakes (equivalent to almost twice the area contained within the Grande Raccordo Anulare of Rome, to be clear) and has transformed the mountain into an amphitheater 500 meters deep and with a diameter of about 2 kilometers.
The eruption of Saint Helens in 1980, therefore, started a strong technological development, with the implementation of new methodologies (and with the refinement of existing ones) for the study of seismicity, deformation, geochemistry and of the remote sensing, but also of communication and collaboration between all the actors involved in volcanic emergencies, not only in the USA but widely in many other parts of the world (such as, for example, Europe and Japan), with Italy playing a fundamental role .
Another major breakthrough following this massive eruption came in response to one of the biggest tragedies caused by volcanic eruptions in recent times. On November 13, 1985, five years after the eruption of Saint Helens, another large American volcano erupted, the Colombian Nevado del Ruiz, which caused over 25.000 victims (to give a proportion, the victims of Saint Helens in 1980 had been 57 …) due to the mud flows that destroyed the town of Armero and several villages located more than 60 kilometers away from the volcano. Driven by this other avoidable catastrophe, thanks to the experience acquired especially during the eruption of Saint Helens, the Volcano Disaster Assistance Program (VDAP) was created by USGS and a US government agency, a program aimed at providing expertise and equipment to countries threatened by volcanic eruptions to monitor and deal with the phases of unrest and the eruptive phases. This has led the VDAP to provide support, mitigate risk and save countless lives during dozens of volcanic emergencies in dozens of countries.
Well, the 1980 Saint Helens eruption was in a sense the "the" for all this, the spark that allowed, globally, a decisive upgrade in volcanic monitoring and surveillance, and this is why we can say that it marked a real turning point in the history of volcanology.
What exactly happened at Saint Helens?
It all started with the appearance of seismicity starting from March 16, 1980, to which were added, from March 27, explosions of modest energy in the crater area and the concomitant and progressive swelling of the northern flank of the volcano. This last phenomenon, in particular, has completely changed the morphology of the mountain.
At 8:32 on 18 May, the actual eruption began with a sectoral collapse: first a M5.2 earthquake under the volcano, then a landslide, which depressurized the volcanic system giving rise to the lateral explosion (lateral blast) of the bulge on the north flank which took place just before the development of the vertical column of the Plinian eruption which lasted nine hours and reached 25 kilometers in height. The maximum speed of the lateral explosion was just over 1.000 km/h.
The eruption then continued, on and off, until the beginning of 1991 with about 20 eruptive periods.
You told us earlier that at the time, USGS colleagues were "accustomed" to different volcanoes, effusive ones, such as those on the Hawaiian islands. What kind of volcano is Saint Helens?
That's right: while Hawaiian volcanoes, such as Kilauea and Mauna Loa, are so-called "shield" volcanoes, Saint Helens is a stratovolcano, generated by the collision between two tectonic plates. In that area of North America the Juan de Fuca oceanic plate "slides", going into subduction, under the North American continent, giving rise to the Cascade Range of which Saint Helens is a part. In this case, the subduction process leads to the formation of magmas which, mainly exploiting the difference in density with the surrounding environment, go back up giving rise to these volcanoes located between Canada and the states of Washington, Oregon and California.
Had Saint Helens already produced similar eruptions in the past?
Yes, even if we have no direct evidence and all the information in our possession comes from geology. The last major eruption of Saint Helens dated back to 1857, but it hadn't produced anything like that which happened in 1980. Eruptions similar in terms of events to that of May 18, 1980, thus capable of generating lateral explosions, occurred about 1000 years ago : there were two and they were in any case much smaller than the one we are remembering today.
Eruptions larger than that of 1980 of which there are geological traces occurred about 3.500 years ago, with an estimated volume 4 times greater than in 1980, and about 20.000 years ago. The latter produced landslides whose thickness was later measured to be about 250 meters, with a volume almost double that of 1980.
What is the state of this volcano today?
Today, Saint Helens is a quiescent volcano. It has seismicity, outgassing and thermal anomalies meticulously monitored by the USGS at the Cascades Volcano Observatory in Vancouver, Oregon, but nothing that is not "commonplace" for a volcano like this.
Were there any other eruptions after 1980?
Yes, the last eruptive phase occurred between 2004 and 2008 and, accompanied by explosive eruptions of modest energy compared to that of 1980, led to the extrusion of lava domes inside the crater "pushed" out of the volcano like the paste from a toothpaste tube. These highly viscous lava domes and spines have reached heights of over 250m.
Are there other volcanoes in the world that have historically produced eruptions similar to that of Saint Helens?
Absolutely yes, and there is an incredible story behind all of this that connects some of the most important scientists who worked on Saint Helens!
In 1980, immediately north of St. Helens was a USGS outpost, Coldwater II, located 10 kilometers inside the government red zone and about 10 kilometers from the crater, from which scientists could observe and monitor the deformation of the crater. volcano, which in the last days before the eruption was of the order of two meters every 24 hours.
Harry Glicken, 22, was the young volcanologist who was on duty at Coldwater II on May 17, 1980, the day before the eruption: that evening he asked for a replacement to be able to return to the University of California at Santa Barbara for a meeting regarding his doctorate. In his place Don Swanson, volcanologist at the USGS, offered himself, who due to a further commitment contacted another young volcanologist, David Johnston (30 years old), mentor of Harry Glicken, who reluctantly accepted the replacement and who on the morning of May 18 it was literally blown away by the volcano's lateral explosion.
The particular morphology left by the eruption was later also found in other volcanoes, including Bezymianny, in Kamchatka, whose morphology had been hypothesized to have a genesis similar to that of Saint Helens.
Harry Glicken, who narrowly escaped the eruption of Saint Helens in 1980, was one of 43 victims of the June 3, 1991 eruption of Mount Unzen, Japan, along with French volcanologists (and spouses) Maurice and Katia Krafft.
The Kraffts, who have become famous in the history of volcanology, are also particularly important to me because it is also thanks to their books (the first of which was given to me by my mother) and their documentaries that I have been able to discover and cultivate this great passion of mine .
Speaking of the Krafft spouses, think that while they died on Mount Unzen in 1991, a video of theirs made to raise awareness of the volcanic risk, “Understanding volcanic hazards” produced for IAVCEI and UNESCO, it was shown to the inhabitants of the slopes of the Pinatubo volcano, in the Philippines. The volcano was giving clear signs of unrest but the locals did not want to abandon their homes. Well, after seeing the images shot by the two volcanologists, many were convinced to leave the area (only one indigenous tribe remained, the Aetas, who lived on the volcano): Pinatubo erupted a few days later, on June 15, causing enormous devastation (and wiping out the tribe that refused to leave) in what would be the second largest eruption of the century after Alaska's Novarupta Volcano in 1912.
During a business trip to Hawaii that I took just a few months before the great eruption of Kilauea in 2018, I got to know Don Swanson, one of the leaders of the USGS during the 1980 eruption. It was a unique opportunity , during which I was told firsthand many of the stories I had read about Saint Helens. After the 1980 eruption, Don Swanson was the first to go looking for David Johnston in a US Army helicopter, but the violence of the explosion had changed the mountain's appearance so much that he was not able to immediately recognize the point where the young colleague's camper should have been, place where the "Johnston Ridge Observatory" visitor center was built in 1997.
What is the most interesting aspect of this volcano and the 1980 eruption for a volcanologist like you?
I would say the human one and the scientific one, to the same extent. The scientifically most interesting aspect of the Saint Helens eruption for me is certainly the lateral blast, the lateral explosion of the north side of the mountain which with its force knocked down all the trees for tens of kilometres, an unprecedented violence. Humanly speaking, imagining a young scientist who saw the explosion coming upon him is truly creepy. The last message sent by David Johnston that morning of May 18, 80, as soon as the landslide began, was: “Vancouver, Vancouver, this is it!”, "Here we are!".
I began to be passionate about this story in 1993, when during the Geology course at Sapienza University Professor Civitelli told us the story of this young American volcanologist: behind this passion of mine, therefore, there is an enormous human component. In the case of Johnston, despite being one of the supporters of the theory of the possible lateral explosion of the volcano (at the time nothing like this had ever been seen, so there was a great scientific debate around the developments that the activity of the Saint Helens might have had), nevertheless went on site to replace a colleague. He showed enormous passion and interest, which I also recently rediscovered in the latest book on Saint Helens that I bought (the latest in a long series…) which has Johnston as the protagonist: “A hero on Mount St. Helens”.
I must say that when I found myself in front of this impressive volcano, in February 2018, I was speechless and in a second it seemed to me as if I were reliving as a protagonist everything I had read over the years in so many books: a huge emotion and unforgettable.
Link to the in-depth article on the INGVvulcani Blog: