March 31, 2021: Grimsvotn, which is not near the active eruption on the Reykjanes Peninsula, still slumbers. Its name, by the way, means “gray water.”

August 15, 2020, 9:11 a.m., Pacific: Good news, but I’ll keep the post pinned for a while, just in case.

August 14, 2020, 6:02 p.m., Pacific: An outburst flood may be starting, but they can’t verify it yet. This tweet thread gives the gist, but the Met Office also has the news posted on its Icelandic site.

Original post:

We’re stepping outside the Decade Volcano series today to look at the most active volcano in Iceland.


For two reasons:

  1. To the delight of tabloids everywhere, risk assessment experts at Deutsche Bank reportedly told their clients last week that there is a one-in-three chance of a major catastrophe in the 2020s.

    Their “doomsday list” includes the possibility of a very large volcanic eruption, on the scale of Mount Tambora in 1815 (which gave us the “Year Without a Summer” and led to the worst famine experienced in Europe and North America in a century: it took an estimated 49,000 lives across the globe [Brown et al.; Oppenheimer]). That’s just what we don’t need to hear right now.

  2. Iceland’s Grimsvotn Volcano is not anywhere close to being another Tambora, but it’s in the news, we’re all on edge because of the tightrope that COVID-19 has us all walking, and memories of major air traffic disruptions from Icelandic eruptions in 2010 (Eyjafjallajokull) and 2011 (Grimsvotn) are fresh.

  3. It’s very easy to jump to gloom-and-doom conclusions right now.

    This is therefore a good time to point out that there is no connection between the Deutsche Bank report, which was based on unrelated research, and the interesting news about likely activity at Grimsvotn in coming days and weeks.

    Here’s what’s happening at Grimsvotn, in a nutshell — volcanologists noted signs earlier this month that magma is close to the surface in the same part of the caldera that hosted eruptions in 2011 (VEI 4) and 2004 (VEI 3).

    What a VEI 4 eruption can look like. For comparison, Tambora’s 1815 blast was VEI 7.

    However, most of that caldera sits under some 700 feet of glacial ice, so the most likely outcome of all this extra heat is a glacial flood.

    These are awesome!

    A look at the current webcam view, looking across the river at glacier-covered Grimsvotn (just a few dark rocky peaks rising above the ice sheet), might lead you to believe that such a flood is already underway.

    Not so, at least at the time of writing (June 18th; will update if something happens between now and Sunday morning).

    That’s an ordinary river flowing across a vast plain of deposits left by previous jokulhlaups.

    This is the sort of thing they expect from Grimsvotn some time soon:

    I couldn’t find online video from Grimsvotn. This glacial outburst flood happened at Eyjafjallajokull in April 2010.

    You get these wherever fire and ice meet, but the floods in Iceland are so dramatic that volcanologists around the world use the Icelandic term for this phenomenon: jokulhlaup.

    Now, research has shown that Grimsvotn does sometimes erupt when its magma chamber is highly pressurized (as it probably is now) and the heavy weight of water in the subglacial caldera suddenly disappears in a jokulhlaup.

    But that BOOM! doesn’t always happen. Volcanoes are very complex systems, especially in Iceland.

    Here’s the bottom line, per the experts at the Met Office:

    • A glacial outburst flood at Grimsvotn will probably happen soon.
    • There may be an eruption, too, but it’s not likely to be as intense as the one in 2011.

    This will be exciting to watch, and it potentially could have some human repercussions, but it’s not going to be the end of the world.

    By the way, many of us outsiders find the names of Iceland volcanoes challenging.

    I did a post about that, a while back — it includes some spectacular guest videos, including one that brings you up close and personal with Grimsvotn.


    64.416° N, 17.316° W, in Austur-Skaftafellssysla/Vestur-Skaftafellssysla, Iceland. The GVP Volcano Number is 373010.

    Nearby Population:

    Per the Global Volcanism Program:

    • Within 5 km (3 miles): 0
    • Within 10 km (6 miles): 0
    • Within 30 km (19 miles): 0
    • Within 100 km (62 miles): 1,736

    Current Status:

    Normal, Aviation Code Green.


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