Summary: The volcanic eruptions in Iceland reminds how geological events can make the works of man look insignificant. Fortunately this happens seldom, as we reckon time. This post discusses the possibility that the current eruption cycle in Iceland might become larger and more destructive.
Much of the media discussion about the odds of the current eruptions becoming far worse comes from “Katla and Eyjafjallajokull Volcanoes“, Erik Sturkell et al, October 2009 — Chapter 2 of volume 13 in the book series Developments in Quaternary Science. The controversial quote concerns the odds of an eruption from the adjacent and far more powerful volcano Katla (red emphasis added}:
“The neighbouring volcano Eyjafjallajökull has erupted twice, simultaneously with Katla. … The high level of seismicity associated with inflation of the volcano {Katla} during this period suggests that the volcano is close to failure and a new eruption or intrusion event may be initiated if magma flow towards shallow levels resumes.”
Does this accurately describe the situation? This post provides more detail so that you can decide for yourself.
- Abstract of the article
- Excerpt from the article
- An example of doom-mongering
- Other posts about volcanoes, and an Afterword
(1) Abstract of the article
The Katla volcano is covered by the Mýrdalsjökull ice cap and is currently one of the most active volcanoes in Iceland. It has erupted twenty times the past 1,100 years. The neighbouring volcano Eyjafjallajökull has erupted twice, simultaneously with Katla. As glaciers cover both volcanoes, their eruptions are phreato-magmatic by nature. The volcanoes are located directly south of where surface expressions of the rift cease. Seismically, Katla is one of the most active volcanoes in Iceland, showing an annual cycle in activity, observed from at least 1960 and less pronounced since 2004. From 1999 to late 2004, GPS measurements revealed steady inflation of the volcano, showing uplift and outward horizontal displacement. Until 1990s, Eyjafjallajökull had been seismically quiet for several decades. Seismic activity there was high in 1994 and again in 1999, related to the emplacement of two intrusions. Source
(2) Excerpt
The volcanic system of Katla is one of the most active ones in Iceland with at least 20 eruptions within the central volcano and one in its fissure swarm during the past 1,100 years. The volcano is covered mostly by the Myrdalsjokull ice cap … The neighbouring volcano, 25km to the west, is Eyjafjallajokull. It is currently much less active, with two eruptions during the past 1,100 years, occurring in tandem with Katla eruptions in 1612 and 1821–1823. The erupted volumes from the Eyjafjallajokull volcano have been negligible in historic times and range in the 0.1km3 scale.
… Katla stands out among Icelandic volcanoes for its high and persistent seismic activity. The only other volcanoes that compare to Katla in this respect are Hengill and Barjarbunga, both of which are located on main branches of the plate boundary.
… The inferred volume of magma accumulated in a shallow magma chamber at Katla during the 1999–2004 inflation period is approximately 0.01 km3. This volume is miniscule compared to the erupted volume in 1918, when about 1 km3 was erupted. The new magma was emplaced at shallow levels within the plumbing system of the Katla volcano. The high level of seismicity associated with inflation of the volcano during this period suggests that the volcano is close to failure and a new eruption or intrusion event may be initiated if magma flow towards shallow levels resumes. New material has been added to the shallow magma chamber, rather small volumes in this case, but this can thermally lubricate the pathways for deeper seated magma and give a fast track for the material to reach the surface. With the volcano in an agitated state, an eruption can take place without prolonged precursory signals. However, these effects decay with time as the magma solidifies unless new material is added.
Furthermore, the suspected cryptodome can cause explosive volcanism if it ascends above the ground and makes a dome, which can collapse and generate pyroclastic flows, or, if a basaltic magma intrudes into a rhyolitic cryptodome. In addition, basaltic eruptions that take place under the Myrdalsjokull ice cap will be phreato-magmatic. This, together with a possible differentiation of the material in a shallow magma chamber, favours explosive activity, possibly reaching plinian magnitudes.
Plinian means volcanic eruptions similar to that of Mt. Versuvius in AD 79, with gas and ash shot into the stratosphere. Mount St. Helens (1980) and Krakatoa (1883) are other examples. See Wikipedia for more about this.
(3) An example of doom-mongering (earnest reading of dubious websites can make us dumber)
“Katla Earthquake May Presage Next Volcanic Explosion“, Zero Hedge, 17 May 2010 — “As earthquakes tend to not be an indicator of volcanic stability, the most anticipated volcanic explosion in human history may finally be a fact quite soon.”
Here are the facts — for people interested in real information, not fun nonsense:
- Iceland has many small quakes, shown in this graphic of Earthquakes during last 48 hours at the website of the Icelandic Meteorological Office. Also see the long list of recent earthquakes.
- The excerpt shown above says that Katla is known for “its high and persistent seismic activity.”
- Their Met Office’s page about the Eyjafjallajökull eruption has the headline “Katla is NOT erupting and there are NO indications that Katla is about to erupt.”
- For an explanation of this activity see “Katla seismicity“, Heidi Soosalu, Institute of Earth Sciences at the U of Iceland.
(4a) Other posts about volcanoes
- About our certain doom from the Yellowstone supervolcano, 11 January 2009
- Global warming causes earthquakes and volcanic eruptions (yes, this story is real), 17 April 2010
- More about shockwaves of the volcanic kind, 21 April 2010
(4b) Afterword
- For more about this website, see the About the FM website page.
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