Deep Space Live 26.9.2013 Ars Electronica Center
by Birgit Hartinger
The most dangerous volcanoes of the world, presented in the series „In Touch with the Earth“ in the AEC.
While preparing for this speech I came to notice that people, especially younger folks do not really know what a volcano is and even less what destructive force it can hold within. Many younger people only think of some unpronounceable Icelandic volcano that spit some ash in 2010 which disrupted air travel and caused some inconvenience. So I thought it to be wise to give some information about some rather recent eruptions which made their way into the press during my life time.
This also gives me an excuse for not really providing spectacular images as would be fit for a screen 16 by 9 meters. Photography was just not as advanced when Mount Saint Helens and Pinatubo erupted.
Mount Saint Helens did the big thing on May 18th 1980. Before it had been an almost perfectly cone shaped volcano which lay dormant for centuries. Many people only saw it as pristine vacation area. An ideal site for fishing trout in Spirit Lake or summer camps for the youth. It also harboured the best timber of the world, as some woodcutters stated.
In early 1980 a series of earthquakes started and some cracks in the ice started to appear. Later a column of “smoke“ started rising into the air close to the top. It was clear to the volcanologists, Mount Saint Helens was waking up. New instruments were brought to the mountain. With seismometers ( there had only been one up on the mountain) and with new laser technology scientists started measuring the volcano to see how much the bulge forming on the mountain top was rising day by day. When they found a rise of 5 feet ( approximately 1,5 m ) they sent the instruments back to have them checked because they believed the measurements must be faulty. It turned out they were accurate and the bulge really rose at a rate of 5 feet per day.
Then on early May 18th a call from scientist named David Johnston reached the center: Vancouver… Vancouver this is it! (Famous last words.) When an eruption started suddenly the northwest flank of Mount Saint Helens gave way and a major landslide occurred, the biggest one in the history of the United States. This left the throat of the volcano open and so the eruption happened on a far bigger scale than previously predicted. The material sliding down the side reached Spirit Lake and swept across a ridge causing a major lahar. (= a mudflow, one volcanic hazard explained later in the speech.)
To cut a long story short. An area of 60 km2 was flattened, some casualties (57 to be exact) had to be recorded, mostly people who were either too stubborn to leave, or scientists who stayed too close to the mountain and some campers who were also too close, because the flank failure could not be predicted. The ash cloud sent upwards caused the climate to be one degree colder the next 2 years.
And then came Pinatubo in 1991.
This event might not have been as well recorded if there had not been an United States Air Base in the vicinity, Clark Air Base. But the potential threat to American citizens made the government send geologists into the area to try to find out what was going on. There had been many earthquakes during a period of 2 years beforehand. One of them a rather impressive 5.4.
The scientists did not have an easy job because if they had called for an evacuation and nothing had happened, people would lose their trust in them and might not be motivated to leave when the next evacuation plan was ordered. But studying the area’s older ash deposits and especially the thickness of the layers left behind from ancient lahars clearly showed that Pinatubo has the potential to be a monster. So, again the short version. After months Pinatubo started with minor eruptions, but the scientists believed it was only clearing its throat. Finally they called “red alert” and Clark Air Base was cleared.
Scientists had stated a major eruption was imminent within the next 2 days. Some hours after the deadline of 2 days, it really happened and Pinatubo blew an ash column over 30 km into the air. There were not as many victims of the eruption as there would have been without the call for an evacuation by the American scientists, but only those who left right after Clark Air Base was abandoned were saved. The lahars streaming towards the coast left hundreds if not thousands of people dead, as did the starvation which followed.
One thing that has to be mentioned: Unfortunately the eruption occurred during a typhoon; so the ash was distributed over a much larger surrounding area than it would have been without the storm. Pinatubo’s 1991 eruption is said to have caused a cooling of the earth’s climate by 2 degrees in the following 2 years. Meanwhile Pinatubo has calmed down and a beautiful lake has formed inside its crater.
Mount Saint Helens and Pinatubo had global volcanic effects. Eyjafjalla was a local event, if airplanes had not been invented, no one would have noticed anything different here in Middle Europe.
So volcanoes can have local and global effects. The explosiveness of volcanic eruption is calculated in VEI Volcanic Eruption Index.
People on VC seem to agree that this is not the most perfect tool to determine the real danger of a volcano because it only shows the amount of emitted material in cubic tons but does not take the time in which this happened into consideration. Everything above VEI4 is a major event, but Grimsvotn spat out more material in 3 days than Eyjafjalla did in months and hardly anyone in Europe even noticed (besides us volcanoholics of course).
Next I´ll be trying to explain the different hazards volcanoes can bring.
Please take into account, that this is a talk for people who have near to no knowledge about volcanoes and I want to get them fascinated with my hobby.
Here is the announcement for the lecture on the museums Homepage (in German):