It is a strange one. Metals are shiny, and this one certainly is, in a dark-grey, silvery way. It is so shiny that it can even be used as a telescope mirror. Metals tend to be hard, but this one certainly is not. It isn’t even a solid. Mercury is one of only two elements that are liquid at room temperature (the other one is bromine). It freezes (an unexpected word to use for a metal) at a chilly -38 C. A liquid state may seem to be a bit of a problem when using it as a mirror: pour it on the parabolic surface of a telescope mirror base, and it collects at the bottom. But uncooperative physics never stopped astronomers. If you let the mirror rotate (at just the right rate), the centrifugal force will make the mercury spread out, so that it covers the whole surface in a perfectly reflective layer. A slight problem is that it only works while the telescope is vertical: any other angle, and the mercury will sink down. This is a mirror that can’t point. You just have to hope that there is something interesting to look at at the zenith.

There are other limitations: you can’t use it in Antarctica or in the Polar regions (the mercury would freeze), and there is a tendency for your mirror to evaporate with rather poisonous vapour. But you could build a massive ten-meter mirror in your back garden for just a few million. When astronomers dream, they dream of mercury.

The Liquid Mirror Telescope, operated by the NASA Orbital Debris Program Office at the NASA Orbital Debris Observatory in Cloudcroft, New Mexico from 1996 to 2000.

But mercury has more uses than just in astronomy, and it reveals more than just the Universe. It also provides a window to the past and its ancient volcanism.


Let’s first look at the chemistry. The periodic table is a good place to start. It can take a while to find mercury: it is quite far down, in the 6th row: look for element number 80. It is in illustrious company, coming immediately after platinum and gold. The two following elements are thallium and lead, if you are interested.

Many of the elements of the 6th row are very dense. Mercury is not the most dense (Osmium has that claim), but it still 13 times the density of water, and 20% denser than lead. This is a true heavy metal – it rocks.

Looking at the vertical columns in the periodic table, Mercury is in the so-called ‘group 12’ elements of the periodic table (zinc, cadmium, mercury). These share low melting points. They also have low reactivity – they are reluctant to form molecules, because their main electron shell is full. If you can imagine your heavy metal band being a solo artist, that is mercury.

But this does stop it from forming molecules. Compounds with mercury include HgF2, HgCl2, HgBr2, HgO2 and HgS2. The last one is the most important one. More complex molecules can also form, such as Hg2SO4. But there are no reactions with iron, and therefore mercury is normally kept in iron containers. On the other hand, mercury reacts well with aluminium, and for this reason it is not allowed on airplanes.

Mercury is a poisonous element. But put it in a compound and it becomes highly poisonous. The worst of those compounds is methylmercury, which contains CH3Hg. This neurotoxin readily forms when mercury circulates in water, and it enters the food chain through fish. The most common cause of methylmercury poisoning is indeed from eating fish. Whale meat can be particularly high in methylmercury.

One gram of methylmercury can be fatal, and because it takes many months to leave the body, this dose can build over months. In the US, a safe dose is considered less than 1 microgram per day per person. Afflictions caused by methylmercury can include fatigue, vertigo, headaches, mental decline, progressing into shaking and eventually death. The French physicist Blaise Pascal, who used mercury in his research, may have succumbed to this. He suffered from poor health, with worsening headaches, and he complained about losing his ability to concentrate. Pascal is often said to have suffered a low grade brain tumour, but mercury poisoning seems to fit the symptoms as well. Quem Mercurius perdere vult, dementat prius. In Japan, methylmercury poisoning is known as Minamata disease, named after a particularly nasty case involving an unscrupulous company which at one point stopped investigations by installing a fake water treatment system. In the Roman Empire, people working in the mercury mines developed a shaking which became known as ‘mercurial’.

In the past, the closely related substance ethylmercury was used as a pesticide. It wasn’t the most toxic of the pesticides in use, but it came close. Eventually its use was banned.

Once ingested, mercury stays in the body for a long time. After the intake of mercury is stopped, recovery can therefore take several years.

Methylmercury builds up at the apex of food chain of the oceans. This is why whales can reach high levels (their longevity may also play a role). You do wonder whether they suffer from the same symptoms as we do: vertigo, fatigue, and headaches.

Mercury is less dangerous to us in its metal form, because it is not easily absorbed by the skin – although contact should still be avoided. But where there is liquid, there is also vapour, and the mercury vapour is far more dangerous. That is what can make liquid mercury dangerous to have around: the vapour can be inhaled.

The ecology of mercury

Mercury has a complex life cycle: it circulates between the atmosphere, the soil and the oceans. In the atmosphere, mercury lasts for about a year. It exists at very low concentrations, though. Eventually it oxidizes and in that form is dissolves into water. So rain removes it and it enters the soil and oceans. Oceans slowly lose it back to the atmosphere, mainly through waves. Both on land and in the sea, mercury binds readily to living organisms. In the sea, this brings it into the food chain. On land, a lot ends up in trees. The concentration of mercury in living organisms is called bio-amplification.

Trees take in much of the mercury and they are good at keeping hold of it. Forest fires release it back into the atmosphere. The trees that formed the coal reserves brought their mercury with, and so coal has a higher amount of mercury than typical rock.

The natural input of mercury into the atmosphere comes from oceans and trees. Human emissions exceed the natural ones. Much of this has come from coal burning. Although mercury levels in coal are not very high, we burn a lot of coal and the total adds up. There are international agreements in place that have considerably reduced this, and these emissions have declined by 90% since 1970. Not all news is bad! At the moment, coal burning is estimated to account for 25% of our mercury emission, and it is no longer the largest source. The largest contribution nowadays comes from gold mining.

However, mercury stays in the environment for a long time. Trees still have high levels from our past emissions, and they release this into the atmosphere. At the moment, mercury emissions into the atmosphere are still at about twice the natural level largely because of the memory effect.

The total natural emission is around 1000 tons per year, anthropocentric emission is around 2000 tons and legacy emission amounts to about 6000 tons. Our history clearly still matters. But our improved mercury management is paying off: mercury levels in the Atlantic Ocean are now falling.

Source: UN Global Mercury Assessment, 2013

The figure shows the full cycle, with the natural and anthropocentric emissions indicated. The red/orange striped arrows indicate ‘re-emissions’ which are caused by our much larger emissions of the past. For instance, mercury in trees remains in storage until someone lights a match. Forest fires then become major source of re-emission of the stored mercury. Emissions from the oceans, as mentioned above, are also largely legacy mercury. The re-emitted mercury remains in the atmosphere for around a year before it re-enters the sea or the soil.

Eventually, the mercury ends up under ground. This happens mainly through buried organic material. Sediment and decaying vegetation become mercury’s final resting place. Sediments can build up over time to amazingly thick layers. Over ten kilometer of sediment is not impossible, as the sea floor sinks under the weight. Mercury can therefore become deeply buried, albeit at low concentrations, within much of the continents.


In the Earth’s crust mercury mainly combines with sulfur. Mercurysulfide does not dissolve in water. It remains solid, and forms a mineral called cinnabar. Cinnabar can be stunning. In crystal form it is bright scarlet to red, and it looks like a deeply coloured quartz. This is rare, however, and normally it is a soft, brick-red rock. It is a hydrothermal mineral which is deposited on the surface of other rock.

It is the basis of vermillion, a pigment that can range in colour from orange to purple, and was commonly used in paintings. Nowadays it has been largely replaced by cadmium red, equally red but less poisonous.

Some less than fully trustworthy web shops offer cinnabar for its healing properties (the words ‘crystal healing’ are the warning sign). These claims should be taken with more than just a grain of salt – a pillar would be more like it. If you feel that ‘crystal healing’ is harmless, not in this case. Cinnabar is potentially the most toxic mineral known to us. Mercurysulfide itself is not as poisonous as other forms of mercury, but skin contact should be limited (mercury rash is a warning sign), and although it does not vaporize, inhaling the dust is dangerous. Google, Amazon and Ebay remain happy to advertise cinnabar’s ‘healing’ (but life-shortening) properties. One company even has named a perfume after it; although it contains no mercury, the name is about as appealing and healthy as breathing in oil (also known as vaping).

Liquid mercury can be obtained from cinnabar by heating in an oven, followed by condensation of the mercury vapour and collection in iron containers. However, do not try this at home.

Cinnabar is a fairly common mineral, and is mined for instance in the Red Devil mine in Alaska. About a third of the world’s production comes from Spain. It is found in deposits associated with hot springs, and in veins within rock. As a hydrothermal mineral, it is associated with circulating hot water. This establishes a firm link with volcanoes.


Etna, one of nature’s confirmed mercury emitters

The typical level of mercury in ordinary rock is 0.1 ppm, a negligible amount. In contrast, cinnabar can have 86% concentration HgS. The way to achieve such concentrations involves volcanoes. And plants.

Mercury is a volatile element and can readily end up in melt inclusions. An example is granite, partially melted rock formed at depth underneath mountains. As it comes up, granite can bring the mercury with it, and indeed granite can have twice the mercury concentrations of other rocks (still only 0.2 ppm). Magma acts similarly, and as it rises in the crust it too carries mercury. Magma reservoirs become the main accessible reservoir of mercury.

Now there are two ways to the surface. One is by water circulation, and indeed cinnabar mines are often located in deposits of ancient hot springs. The second is directly from the magma itself, during eruptions. Mercury is too volatile to remain in lava, and it is released in the gas emission, both during an eruption and in steam vents (solfataras). Etna and Hawai’i are both confirmed mercury emitters. So is Yellowstone, with the proviso that USGS measurements found that the wildfires around the park emit more mercury than the geysers do.

Mercury deposition in a North American ice core. Source: UN Global Mercury Assessment, 2013

The figure shows the mercury concentration measured in an ice core from the Upper Fremont Glacier in Wyoming. The green spikes are volcanic emissions, orange is the gold mining, and red is the industrial emission. The human emissions dominate over volcanic ones. This already shows the importance of our emissions. The gold rush was a local event which was less significant on a global scale, but that it true for the St Helens eruption as well.

The ice core above gives an idea of the resulting mercury levels: the spikes due to volcanoes correspond to about 10 ppb. St Helens caused an equally large peak as Krakatau, although it was a less significant eruption. That shows that proximity is important: more mercury is deposited near the eruption. But Tambora also shows up: mercury can travel a long way.

But there are times when nature wasn’t so well behaved. Recent work has shown that at times, volcanic mercury was rampant. And this had consequences.


We live in volcanically quiet times. At times a volcano erupts and causes havoc, but only the immediate surroundings are covered in lava. Occasionally a supereruption goes off and affects half the world, but that is just one of those things and the planet recovers soon enough. But there are times when life is more exciting (and potentially short). A major rift opens up and lava comes out in huge flows, covering large areas in kilometers-thick layers. These eruptions are not instantaneous: they keep erupting intermittently over perhaps 100,000 years or more. They are called LIPs, for Large Igneous Provinces. Typically they last for half a million years. Several of these enormous eruptions coincide with world-wide mass extinctions. The largest of them all was the Siberian Traps, 252 million years ago, which covered much of Siberia (the name gives a clue) and wiped out 99% of life. The extinction, almost a global sterilization, acted through a combination of global superwarming and oxygen depletion.

In our current, quiet times, volcanoes emit around 80 tons of mercury per year. One might expect that in LIPs, this will have increased. Indeed, so it was found. Because a LIP can substantially change the world, they often define the transition of one geological era to another. At these boundaries, mercury levels spike. This is the case for the Permian-Triassic boundary, the Trassic-Jurassic boundary, and Cretaceous-Tertiary boundary (now known as the Cretaceous-Paleocene boundary). These transitions coincide with the Siberian Traps (252 million years ago), the Central Atlantic Magmatic Province (201 million years ago), and the Deccan Traps (66 million years ago).

All three coincided with mass extinctions. For the Deccan Traps the extinction was not solely caused by the volcanoes, as the huge impact in Mexico provided the dinosaur killer blow, but it did not help. All three boundaries coincide with a significantly enhanced level of mercury in the environment.

Flood basalts and large igneous provinces (LIPs). Source: wikipedia

Siberian Traps

This eruption is famous for causing the PT extinction event, the closest the Earth has come to sterilization. It caused extreme global warming where the oceans reached 40C. Photosynthesis ceased and large oxygen declines occurred in the Tethys seas. A bit later, a second pulse spread the oxygen-poor waters across the globe. The Siberian Traps were a huge eruption, but it is not completely clear why it had such a massive impact. There was a major spike in CO2 levels and this explains the heat, but there may have a secondary source of greenhouse heating, perhaps methane.

The extinction stands out in the fossil record. The teeming life of the Permian disappears almost in the blink of the eye, worldwide. The disappearance coincide with the indications for heat and a change in the carbon isotopic ratio. But how about mercury? This also showed a spectacular increase.

Source: Jun Shen et al., Evidence for a prolonged Permian–Triassic extinction interval from global marine mercury records, published in Nature Communications 10, 1563 (2019).

In the figure above, the coloured bands shows the number of genera with their extreme decline at the boundary. The points show the mercury levels in various samples across the world. They are measured as fraction of total organic carbon (TOC). Background levels both during the Permian and Triassic were around 0.20-0.5 ppb. (Note that the plot gives the number in per cent). But during the Siberian Traps eruption, this increased by a factor of 10, and in some sediments by a factor of 100. The timing coincides closely with the extinction event. Over a 40,000 year period with intermittent eruptions, the Siberian Traps may have emitted 10 tons of mercury per year on average, ten times the normal rate.


A second major extinction event happened 201 million years ago, at the transition from the Triassic to the Jurassic. This is the event which cemented the dominance of the dinosaurs. Before this, mammals were common and competitive. But they apparently were not able to cope with the extinction event, or did not recover fast enough. The proto-dinosaurs saw their chance and mammals withdrew into their hiding places. They would have to wait there for 130 million years, while dinosaurs evolved, diversified and ruled.

The extinction is attributed to CO2 emissions from the Central Atlantic Magmatic province, also known as CAMP. This LIP accompanied the first break-up of Pangea, Africa began to separate from Europe and Central America. The lava and ash flows are found in South America (esp. Brazil), Africa, but also eastern North America (Gettysburg), and in southern Europe. As a break-up it didn’t full succeed. It extended into central Brazil, but clearly that part failed to become an ocean. Sometimes, a rift doesn’t rift.

The extinction event was smaller than the PT event but it was still massive. The abundant tropical reefs disappeared, perhaps related to the acidification of the oceans. This all happened during the first major pulse of the CAMP. The CAMP eruptions continued for another million years, and the biodiversity remained very low while the CAMP was in progress. Only after the eruption had ended did the biosphere begin to recover – but it was too late for those poor mammals. Over the next tens of millions of years reefs re-evolved, but now they consisted of very different types of organisms. The play must go on – but with different actors.

CAMP eruption. Figure from A. Thibodeau, et al., Mercury anomalies and the timing of biotic recovery following the end-Triassic mass extinction. Nature Communications 7, 11147 (2016) doi:10.1038/ncomms11147. It shows a sharp Hg peak durning the extinction interval.

The CAMP eruption polluted the world, and this pollution included mercury. Old seabed sediments in Nevada , which were deposited during this time, show elevated mercury levels for about a million years, i.e. the duration of the CAMP. The main extinction event happens early in this period, and there was a sharp peak in Hg at this time. It seems plausible to associate this with an early peak in the CAMP volcanic activity. The break-up began violently, whilst later the activity slowly petered out.

The Deccan Traps

66 million years ago, while India was moving across the Tethys ocean on its way to a collision with Asia, it met with a hot spot. The mantle plume melted through the Indian crust and erupted on the surface. Out came the Deccan Traps (literally: southern stairs), an immense lava field of 1.1 million cubic kilometers. That may be relatively small compared to the Siberian Traps (4 million km3) and the CAMP (2 million km3). However, the Deccan was five times the volume of the Columbia flood basalt. A high sulfur output did not help. This happened in the middle of an ocean. Life on India itself must have been wiped out. Did it impact the rest of the world? The Deccan Traps coincided with the demise of the dinosaurs. However, so did the exceptional impact of the Chicxulub asteroid. The arguments about which of the two was really responsible have gone back and forth. In fact, neither event seems quite sufficient in itself for the magnitude of the extinction event.

The main phase of the Deccan Traps eruption is called phase-2. There was also a phase 1 and phase 3, but these were much smaller affairs. Phase 2 lasted for three quarters of a million year, and formed a lava sheet which reached a thickness of 3.4 km. In general, the layers are thick and horizontal and remarkably uniform. The flow was not continuous: there are many separate layers, sometimes interspersed with other layers, perhaps weathering of the top surface. Look closely and you’ll find different structures. Uranium dating has indicated that phase-2 had four major pulses, lasting up to 100,000 years each and reaching eruption rates of 10 km3 per year on average. There may have been short-lived phases with much higher eruption rates.

The asteroid impacted while the Deccan Traps eruption was on-going. It hit about 250,000 years into phase-2, about 20-30,000 years after the second major Deccan pulse and 100,000 years before the third pulse. These dates are not absolutely certain but considered likely at the 90% confidence level (Schoene et al., Science 363, 862–866 (2019)).

Hg levels during the Deccan Traps, as measured in Europe. Source: Font et al. Mercury anomaly, Deccan volcanism, and the end-Cretaceous mass extinction, 2016, Geology 44: 171-174

Mercury deposits show the Deccan Traps eruption well, but different locations do not always give the same results. In France, enhanced mercury levels has been found for about 150,000 years around the extinction event. A Danish site also show this. But measurements in India find two mercury spikes, near the beginning and the end of phase-2. The picture agrees with the pulse seen in uranium dating, but the mercury data lacks the high accuracy dates: they tend to be derived from argon dating, which is less accurate than uranium.

Combining the two, the middle mercury peak seen in European sites seem to be a merger of the second and third Deccan pulse. This is also the time of the extinction event, but it appears that this event happened while the Deccan Traps entered a quiet interlude.

Could the asteroid have caused mercury pollution? This seems unlikely as those rocks have very low levels of mercury. However, if it hit in a region with enhanced mercury, the vaporized rock evacuated from the crater may have spread mercury across the world. This is still a matter of discussion. It would be useful to have mercury measurements from American deposits. However, it is also possible that the mercury of this time came not from India, but from burning and dying vegetation.

So what caused the extinction? The jury remains out: it is a race between the second pulse of the Deccan phase 2, called Poladpur, and Chicxulub. The former poured 150,000 km3 of lava across India over millennia, while the second instantaneously vaporized perhaps 100,000 km3 of rock. It was like a modern election, with a choice between two evils and no good.

The role of mercury

Mercury is associated with major volcanic events. Eruptions drive it into the atmosphere, where it remains for 6 months to two years. Once it comes out, it is readily incorporated in organic matter, and ends up in sediments together with the carbon. This makes it a suitable tracer of ancient eruptions, more so than sulphates, which also rain out but do not show up in organic matter. Sulphates are excellent in ice cores but these go back no more than a million years. Over geological times, mercury holds sway.

Volcanoes cause a large increase in mercury in the atmosphere, and this remains visible in the sediments that form at that time. Even at levels measured in ppb (parts per billion) it is an identifiable tracer. And because the levels respond so quickly to the eruptions, it gives a very good view of how the eruption developed.

In the three cases discussed here, mercury remains elevated during the eruption and this shows how long the LIP event lasted. In general, this seems to be a bit less than a million years. But the eruptions do not happen at a constant rate. There are short-lived pulses in the eruption. For the Siberian Traps, these pulses seems to have been extreme, and lasted no more than 10,000 years. The main extinction event is clearly associated with the peak. The CAMP shows several peaks, with one very strong peak which coincides with the extinction event. The Deccan Traps are a less clear cut cases. It too shows several pulses but the relation to the extinction event is not exact. The mercury levels also are not as high, and even without evidence for the asteroid impact, we might well have been looking for a secondary cause for why the associated extinction event was so severe.

But can we be sure these mercury peaks were volcanic? There is a lot of mercury stored in the biosphere, and it is also possible to increase mercury emissions by going after the biosphere. In a mass extinction, the biosphere shrinks – could this cause the mercury peaks? In a way, that is what we a doing now by burning coal: it removes organic (or post-organic) matter and this causes a major of our current high mercury levels. How can we tell whether mercury comes from organic matter or from volcanoes?

In fact, we have some information on this. Mercury comes in a range of isotopes. Most common are the isotopes with mass numbers 204, 202, 201, 200, 199. (Other isotopes are rare, radioactive, of both.) Volcanic mercury has the isotopic ratios of the mantle and crust, which differ slightly from those of the atmosphere and biosphere. Volcanoes show a small excess of 202Hg, and a more restricted range of 201Hg. The differences are not large, and there is some overlap.

Deccan isotope measurements from Sial et al., 2016, Cretaceous Research, 66, 60-81

The results confirm that there is a large component of volcanic mercury during a LIP. However, some samples show a more complex pattern. Several samples from the Deccan era show different isotopic ratios. And for the Siberian Traps, most samples show volcanic mercury, but samples from shallow seas of modern China have a low 199Hg fraction, and this points at wildfires releasing mercury from the biosphere. There have been suggestions that the Siberia Traps erupted through a major coal field and set it on fire, and this could have given a further mercury source. It seems that both disasters had double trouble.

The idea has been pushed further. A series of papers over the past 2-3 years have found mercury spikes at 15 different epochs, including the Palaeocene-Eocene thermal maximum (55 million years ago, related to the opening of the North Atlantic), the Aptian-Albian low-oygen ocean event, 120 million years ago and related to the Southern Kerguelen Plateau and/or the Greater Ontong Java Plateau, the Upper Jurassic, 183 million years and part of the Karoo event, and as far back as the SPICE event of the Cambrian, 500 million years (the last from Puss et al 2019). Even the end of the Snowball Earth has been found to show a mercury spike. There are some uncertainties regarding these. It is for instance not always clear whether the ‘spike’ is significantly above background levels. Mercury is often measured relative to the amount organic carbon, and if the amounts of the latter in the sediment are low, the mercury can appear to spike just because of measurement uncertainties. In some cases there is no evidence for a volcanic episode. The ‘SPICE’ event data suffers from both these problems.

The method is promising but the data is difficult. But a clear result is that all of the 5 known mass extinctions are associated with mercury enhancements. Although they are not in themselves proof of volcanic events, it seems likely that LIPs are the main cause of deadly environments.

Fossil of a Galesaurus from the Permian.

Final point

The study of volcanic mercury has exploded in the past few years. The many studies indicate that most of geological time, mercury is at stable background levels. The identified spikes above this background level are fairly short lived (geologically speaking) and they seem to coincide with LIPs. The LIPs stand accused, and they have no strong defence.

LIPs emit mercury, and because gaseous mercury can last as long as a year in the atmosphere, this pollution spreads across the globe. Levels during LIPs are ten times or more above background levels. Typical mercury levels in limestone are between 30 and 50 microgram per kilogram of rock. During LIPs, this increases to levels as high as 500 microgram per kilogram. And because living matter builds up mercury, the levels in organic matter can become even higher.

This leaves one question unanswered. Can the level become so high that the living matter becomes non-living matter? Mercury, after all, is highly poisonous. Flood basalt eruptions affect the ecosystem pretty badly, as is evident from the fact that they coincide with mass extinctions. These extinctions are attributed to a number of effects which act worldwide, far from the eruption itself. They included sulfur pollution, global heating, and low oxygen levels in the oceans. Mercury has not been considered – but could it contribute to the toll?

The mercury amounts that are measured seem small. But this may be deceptive. The level detected in sediments formed during the Siberian Traps are similar to those found in the badly polluted San Pablo Bay in San Francisco. In people affected by Minamata disease in Japan, mercury levels in their body were 150-200 times those in people in other areas. A 50 times enhancement of mercury emissions may therefore not be insignificant. Is it possible that mercury played a role in the mortality during the extinctions? Several papers cautiously suggest that this should be investigated. Based on the numbers, mercury levels could have been dangerous, and locally it could have been deadly. But it seems for a global mass extinction, more may be needed. Mercury is unlikely to be the main cause. But a contribution can not be ruled out.

An interesting finding is that pollen and spores in sediment deposited during LIPs show a high rate of damage and deformation. That is normally attributed to UV-damage, coming from a thinned or absent ozone layer. But mercury pollution can have a similar effect.

It remains this – a suggestion. But perhaps the deadliest of the volcanoes had a helping hand from this deadliest of elements.

Albert, November 2019


Amazingly mercurious
potentially perjurious
decidedly usurious
morbifically injurious

Invisible mercurial
evanescent ethereal
petrified effigial
of vestigial material

Mercury diversity
geologic mystery
mineralized history
of ancient volcanicity

150 thoughts on “Mercurious

  1. In defence of the mercury mirror telescope – while it is true that the parabolic reflector alone is only truly corrected along the axis of rotation, it is possible to compensate. A suitably asymmetrically deformed secondary mirror can correct for the coma resulting from imaging across the axis, up to significant angles. It is even possible to use this method at several different orientations, provided only that the correcting mirrors do not obstruct each other. Far from only being able to look in one direction – mercury mirrors can be made to look in several directions at once. Laval University have been particularly imaginative in extracting useful functionality from rotating mercury mirrors.

    • Yes, I know. Several radio telescopes use the same technique – Arecibo and FAST. And in a less restricted way, so does the SALT telescope. It allows integration on a single object for a bit longer, perhaps an hour overall in the case of SALT. There was a problem with liquid mirrors with dampening the ripples on the surface. That may have been solved.

      • The good thing nowadays is that telescope mirrors for amateurs have never been so cheap. For slightly under £500 one can buy a good sizable 10 inch telescope.

        I have one, and it is fantastic under dark skies.

  2. 3,1 at Askja:

    09.11.2019 21:36:52 65.042 -16.571 0.6 km 3.1 90.04 1.6 km ENE of Dreki

    • Now 3,5 but quality downgraded to 50 %.

      09.11.2019 21:36:52 65.040 -16.560 1.1 km 3.5 50.5 2.1 km E of Dreki

        • Source(IMO)
          This evening at 21:36 an earthquake M3.4 occurred near Askja. The earthquake is part of an earthquake swarm that started last Thursday. Over 200 earthquakes have been measured in the swarm. Earthquakes are common in this area.
          Written by a specialist at 09 Nov 21:55 GMT

    • Actually outside Askja caldera the swarm seem to center some km norteast of Dreki and Dreki is itself just outside on the north eastern side

    • They are not on the run yet. The name comes from the narrow deep canyon with many strange formations in the walls and rocks. Mosr likely the vikiings saw dragons there when they discovered the place a grey and rainy day with some sulfure smell and perhaps a little shaking…

  3. Thanks for an entertaining and educating post!! Until recently mercury was regularly put into the mouths of hughe numbers of people!!! Dentists used it to fill cavities! Nowdays mostly replaced by plastic composites…

    • It is considered safe for people over 6. People under 6 shouldn’t have fillings anyway. The amalgam is very stable and the rate of evaporation should be low enough that the air you breath stays at normal concentrations of mercury in air. The biggest risk is actually for the dentist when preparing the almagam. I did wonder about the wisdom of cremation for people with mercury almagam.

      • Thanks enough to my early childhood scientific background, I always rejected mercury amalgam at the dentist and always aggressively asked for a mercury-free composite instead, even if more pricey.

        In a world filled with chemical pollution, its wise to avoid intentionally putting toxic metals into your mouth.

        This sort of thing is a bit similar to the more extreme example of lobotomy having been used in the “medieval times” (1940s) as a treatment for mental disorders. The usage of amalgams is going to eventually be seen in the same light.

        Of course the higher classes always went for gold, which is an inert and non-toxic metal.

        But the future is not composites at all. The future is using regenerative medicine, with a mix of fully biodegradable composites and stem cells or growth factors that create the entire regeneration of tooth material and tissue. Perfectly doable and currently a mainstream topic in medical research in labs (I used to do this, during my PhD).

        However hospital (or dentist) practice is often lagging decades behind medical research innovation.

        This was a big source of personal frustration for me. In the lab I experience medical life in the late 21st century only to realize that things out there in the world are so delayed. Two factors explain this: money is one, and the other is that humans are creatures of habit and resist change. For instance, sequencing your genome and knowing all your mutations and issues (aka personalize medicine), detection of cancer markers in the blood stream, full complete regeneration of body tissues. All of this is currently possible, and its only a matter of time until it becomes widely mainstream int he medical centers.

        The other day I explained my GP doctor, that I was going to fully sequence my genome. He first said I was crazy. A few weeks later, he said he was thinking about doing the same! Lol 🙂

        • There is no doubt that better materials are available. Mercury is cheap and easy to work with for the dentist, and the alloy is hard. Some people are allergic to the other metals in the amalgam. Otherwise, if you already have mercury fillings, leave them. If you need new ones, consider alternatives but not to the point of not getting any. They are fairly safe. Regarding sequencing, I wouldn’t yet do it. Medical insurance becomes more complex if you know your risks.

          • Medical insurance: I am in the UK so the NHS service is public and I do not have any medical insurance. I also lived in other European countries where I only used the public system, or the private system but without being part of an insurance package. So I do not see that as an issue.

            In any case, its very easy to sequence a genome and give a false name thereby ensuring one’s privacy.

            But I agree with you, this is going to be a massive issue in the future, when sequencing becomes widely available and even common practice.
            Genome privacy is going to be akin to social media privacy. Everybody is going to try to steal one’s DNA information, so no guarantees about privacy.

            My biggest concern is actually not having enough maturity or the “balls” to be able to handle the information myself. Considering statistics everyone probably has a fair share of mutations in our DNA that makes us prone for some problem! So the changes of being surprised by finding something unusual are pretty high!

          • I believe that the most common issue from DNA testing has been related to parentage. A surprising number of people are not genetically related to one of their parents. Sometimes it is better not to know.

          • eheheh 🙂

            Parentage: such a hot topic!

            But its also so easy to just steal one piece of hair from your father and test your DNA against that… Also its cheap. Though technically illegal without the other person consent.

            Anyways, I am so similar looking to my father (and sharing even a minor and rare genetic disorder) that I am 110% sure that my father is my father. Guess I am lucky with that.

            I agree, sometimes better not to know.

            By the way, is volcanic curiosity genetic inherited?
            Maybe yes:

          • Mercury is probably slightly biocidal, which may be useful. The main problem with UK NHS dentistry is that dentists were not paid for a checkup so you always got a filling. I am pretty certain that all of these were into healthy teeth in my childhood.

            Implants are relatively cheap and astonishingly effective but you do have to shop around.

            Yes, I have done a 23&me, cheap and probably incomplete. Sadly/luckily nothing interesting turned up and I don’t seem to have any unknown interesting relatives.

          • “Medical insurance becomes more complex if you know your risks.”

            More so if the carriers have access to your genome data.

            Unfortunately the gate has already been opened for 3rd party access to genetic data.


            Cute eh? This essentially means that if your data is in that data base. You are automatically a suspect in crimes conducted hundreds of miles away… simply because YOUR genome is being looked at.

          • And you had better pray yo God that your defense lawyer has access to someone with the statistical and genomic expertise to contest a false positive. DNA data is hyped as infallible, though in reality, it’s not.

  4. Askja is likely headed for an eruption. This is my opinion.

    Askja erupted somehow often last century, a few eruptions in the 1920s and one last one in the 1961. When I visited the area in 2010, the entire fissure from 1961 was still hot and releasing steam, so I see that region (NE of Askja) as still an easy pathway for magma to exit. Still somewhat hot.

    Askja was experiencing already several deep intrusions in the 2000s and early 2010s.and inflation.

    Holuhraun was a massive factor in the region. First magma reached almost all the way to the 1961 region. But secondly and more importantly, the Holuhraun area rifted and so the entire region experienced wide GPS movements, including Askja, where strain has probably increased greatly.

    All these things together, makes me think this could be our next Icelandic eruption and quite in soon. I give it
    50% change that this is perhaps the swarm before the eruption. But I would expect larger quakes the days before an eruption.

    Any eruption there would be mostly effusive and relatively small sized. Unless, by some hidden way, Holuhraun added significantly to the volume of intruded magma.

    • Our in-house plot suggests it is tectonic, related to the edifice edge

      • I agree it could be simply tectonic strain by the collapsing caldera.
        The swarm is not deep.

        However in 1961, this is where the eruption started.
        It was proceeded by large geothermal fields suddenly appearing across a N-S line in the caldera’s northeastern edge.

        PS: great map!

        • The swarm is a few kms away from the location of the 1961 fissure and the caldera edge. It could be tectonic or volcano-tectonic but it doesn’t seem to be an intrusion to me.

        • Another burst of activity at that location, looking at the current depths, it looks quite shallow.

  5. Askja 1961 eruption:

    I also remember Askja volcano experiencing a fair share of weird phenomena over the last few years. Rumbles heard by tourists. A massive landslide over the caldera edge (with a local tsunami). The caldera lake being ice-free one winter.

    • PS: I just noticed as I took this photo off the internet, from an Amazon postcard, I cannot guarantee its really Askja. But I had seen plenty of old printed photos from Askja 1961 when I lived in Iceland. And they all looked very similar. The old photos all show a snowy desert landscape, gloomy autumn skies, people standing next to their old 1960s jeeps, and a small effusive eruption, The region is very remote and you need a very big jeep to get there during winter months.

  6. The swarm at Askja continues non-stop. Dozen of small quakes and a few larger ones, and another 3.2 this afternoon. So far all quakes have been rather shallow, located between 2 and 5km deep.

    Some quakes are probably not detected as there is a significant large storm passing near Iceland.

    GPS graphs show slightly more inflation in recent weeks but per se this is not unusual.

    Askja history:
    Askja is a very remote volcano so many of its eruption have not been confirmed during medieval times. It also erupts usually short small effusive eruptions, which could be easily missed during wintertime.
    After the massive VEI5 caldera forming eruption of 1875, which created a long rifting fissure in north Iceland, Askja paused for a few decades and erupted often in the 1920s (about 6 eruptions). Then it erupted again in 1938 and one last eruption in 1961.
    It is thought that this pattern of effusive eruptions also occurred prior to the 1875 eruption. Some might have occurred during the 18th century at the same time as the old Holuhraun eruption, as two volcanic plumes were observed in the region at that time.
    Another caldera forming eruption probably occurred in the early Holocene.

    Probably one of the most outstanding facts about Askja is its very long northwards fissure swarm which reaches the north coast of Iceland and has featured eruptions in the Holocene. Think about something very similar to Holuhraun. I found once an Holocene Askja lava field located very very far away from the central volcano, near the north coast. Magma has travelled on a dike for a distance far longer than Holuhraun and even longer than Veidivotn.

    • Grabbed a screenshot from Fulturevolc, zoomed at the swarm, 48 hours.

      Compared to the activity in the past years region Herdubreiđ and Askja, the swarm is at a spot only few quakes took place (I checked at IanF’s map, since 1995.
      Tectonic, I agree, and same depth as the ‘usual’ swarms more to the east, but interesting spot so close to Askja.

      • I might have been wrong.

        Upon a closer look, the swarm is actually further east than the 1961 site, which is located actually in the north northeastern side of the caldera. Originally I thought the 1961 eruption has occurred at the eastern edge. But I was wrong.

        This swarm is therefore likely be tectonic.

    • How many times more powerful are the hotspot under Iceland than the hotspot under the Azores?
      Azores and Iceland are both Hotspots located near Mid Ocean Ridges.

      But Azores seems so weak it cannot even lift up the spreading ridge above sealevel there.

      • Azores Sao Miguel volcanoes had a few VEI5 eruptions, that formed calderas, in the medieval times.

        The Azores just have been unusually dormant in recent centuries.

        The very tall edifice from Pico island will eventually suffer a massive eruption and form a caldera. Such eruption would certainly be in VEI6 territory.

        • Pico is a basaltic stratovolcano
          The entire edifice is just a few 1000 years old! And mainly clad in pahoehoe lavas.
          The stratocone itself is maximum of 5000 years old I think

          Pico formed through constant very very slow holocene activity.. of fluid alkaline basalts. Eruptions lasted many many 100 s of years each at slow rates.
          Probaly most of the stratocone was formed during a long lived very slow episode earlier holocene.

          Pico was constantly active earlier in holocene.
          Pico island itself is just 25 000 years old at oldest subarial rocks

  7. Curious, do we have any mercury records that do not correspond to LIP’s? LIP’s are enormous, but even they can be lost to geological time. I have to imagine the further we go back in time, the more of these enormous events were lost – some may have been subducted beneath the ocean, and lost to time.

    On a second note, I find the pulsation of flood basalt eruptions rather interesting. I think myself as well as others have viewed these eruptions as long-gradual affairs, but it makes sense that there would be a peak of intensity followed by gradual tapering of output over the subsequent millions of years. This brings me back to thinking about our favorite African superplume. I know there have been research studies in the past pointing to absurd magmatic bodies being identified at certain regions beneath the African rift – I almost wonder if the african rift system is building up to one of these types of spurts. The African rift system may have started 22 million years ago, but we do know that most LIP’s are associated with continental rifting, and if Africa has more rifting to be done, then we could see renewed flood basalts on Africa some time in the geological future. It would be the most logical candidate for the next LIP on earth (although likely far after we are all dead).

    • In response to my first point – I remember reading about some ancient very old LIP’s discovered that ranged over the Canadian shield, and were possibly larger than the Siberian traps. I can’t find a link to the source right now, but I know this exists.

        • It seems that different numbers are used for this province. The volcanic plateau is listed as a volume of at least 500,000 km3 which is more of a typical range. The large area seems to include the entire Mackenzie dike swarm but this may not all be related to the flood basalt. In Africa you can probably find dike swarms underneath the entire african rift, but the flood basalt was (so far) only in Afar. It is big – but how big may be a matter of discussion,

    • CFB is known to have multiple layers, many from different but related rift structures.

  8. So where in the planet is the greatest concentration of mercury? Could an impact on one side of the planet eject it from the other side? As some of you know, I have a hunch that massive impacts change the Earth in ways which take millennia to settle down. Hotspots likewise power the traversing land masses. The theory that Yellowstone is a deep impact which initially smacked the Farallon Plate down vertically, is not a widely accepted theory. The eye of Africa in the Sahara appears to me to be like an exit wound, where something could have pushed the sedimentary layers sharply upwards, fracturing the crystal regions of the circle. And nearby is found uranium in both its spent and unspent forms. India appears to have detached from the Horn of Africa, and the matching areas are near Madagascar and The Deccan Traps, while the land mass in between has continued to split and widen either side of the Rift Valley. Dynamic earth is a complex whole, and mercury is surely a lubricant between the layers?

    • And there seems to have been a foreshock as well

      4.7 26km W of Pepeekeo, Hawaii 2019-11-11 16:35:53 (UTC) 13.0 km
      2.6 25km W of Pepeekeo, Hawaii 2019-11-11 16:33:05 (UTC) 28.9 km

    • Now manually reviewed and magnitude up a bit.

      M 4.9 – 26km W of Pepeekeo, Hawaii
      2019-11-11 16:35:52 (UTC) 19.864°N 155.356°W 32.6 km depth

  9. Significant earthquake underneath Mauna Kea. It is listed as close to M5. There were several foreshocks in the ten minutes before the main shock. I have not heard of any damage, not likely as the quake was quite deep.

      • There may be some traffic signal on this plot as well. The earthquake was around the end of the might when the night crew drives down. The day crew shows up 1 or 2 hours later.

          • In have not heard of any, and would not expect any since telescopes are meant to be earthquake-proof. The VLT has survived an M8 without damage to the telescope.

  10. A bit off-topic. I enjoyed the article on Balls Pyramid very much – never knew it existed, so it was really fascinating.
    Anyhow, the other day quite by chance I came across this video of it:

    • Wow! After that I will never forget Balls pyramid!!!

      Meanwhile, the swarm continues east northeast of Askja, Iceland. Drumplots still dry. Strange with so many quakes in such a small volome of rock. It should all have turned to gravel by now. Maybe it is the lokal dragon moving aground after all!!

    • Glad you liked the article. Thank you. And thanks for the video! For a moment I thought they were going to try and land on the top or something!

  11. Slightly off topic. Sometimes people discuss statistics with regard to volcanoes, and on here, those ideas quickly get shot down from the perspective of “volcanoes do not follow a schedule”. There often is some statistical information in nature, but it’s not often predictive, and often patterns people see are not real.

    With that said, I was working on a project for something unrelated to volcanoes, and it got me to thinking about plugging in my favorite dataset to get an idea of a statistical view of volcanic eruptions.

    See what came out below:

    I took the GISP2 greenland ice core data from NOAA, which displays volcanic so2 trapped in northern hemisphere ice cores dating back to 100,000 years before present. Note that the further back you go, the more data is omitted since the date ranges start to be presented as 50 year gaps, which allows sulfate to filter out of the atmosphere. Regardless, there is some interesting information here…

    The main interesting fact is that based on this dataset, it seems that the distribution of Volcanic so2 has some really fat tails. In other words, a guassian distribution does not fit the model at all. Were you to do a similar analysis of earthquake energy released, you would likely get similar results here – lots of background “noise” (aka small events) followed by periodic spikes that go far beyond what a normal standard distribution would define as being likely.

    • Yes, the SO2 will be dominated by the largest eruption per year. There are not many of those, probably not enough for a gaussian to show up. In effect, you give an enormous weight to very largest events. Have you looked at the timings between spikes? Is that random? Can you reproduce it with a Monte Carlo method? The background levels show a slow fluctuation which a wavelet function may pick out. That is probably climate, not volcanoes.

    • Have you considered regional probability? The amount of volcanoes on the Earth is not static, so it’s likely that regions have a pattern but the entire earth as a whole

  12. I grew up in San Jose, California. In the Coast Range just south of town (New Almaden area) there is a deposit of mercury that was mined in the past. Interestingly, the mercury was found to be filling geodes! Unfortunately, due to the way this was mined, I wasn’t allowed to go fishing in any of the streams in that area….
    I’ve always been curious as to how these geodes formed that way. Most of the coast range was scraped up from the seafloor. Maybe hydrothermal fluids brought it up along the San Andreas fault, which is in that area?

    • The area is known for cinnabar and for geodes, but I had not heard of cinnabar inside the geodes. Mercury is sometimes found with pyrite, and that can be a trace inside a geode. But in general, I would expect that the geode is worth more than any mercury it could contain.

    • Hi kadog,

      I once read a report of a fellow rockhounder who was in an old quarry in Spain to find cinnabar etc. Apparently the geologic setting there is such that after he opened the crystal clefts liquid mercury was actually flowing out of the cleft for a while. It seems during the formation there was an abundance of mercury. When the host rock cooled down the extra mercury apparently was segregated from the cinnabar so that the clefts there are filled with substantial amounts of liquid mercury now. Quite special!

      • crazy – can you imagine smashing a bot off a rock and seeing silver liquid ‘blood’ ooze out

  13. Hello everybody, a new looooong term lurker here.
    Are these amount of earthquakes under Askja realy only tectonic??
    It seems more like an intrusion .

    Greetings from Germany

      • Yes, it appears tectonic. It will include aftershocks from the M3.4 Overall, this seems quite a brittle fault with lots of small cracks rather than one big one. The trigger could still be volcanic, such as an inflating magma chamber somewhere pressing. But to me it looks like movement on the rift.

        • Thought. I agree it looks tectonic. An inflating magma chamber would produce other signals, especially GPS. But, there seems to be a floor to this EQ activity at around 8km; could it be the results of… not a magma chamber inflating per. se. but some kind of magma movement intrusion at depth, where the crust is too hot for brittle fracture, and we only see tectonic EQs at shallower depths because the magma isn’t that shallow so no ‘wet’ or hybrid EQs?

          I don’t know what the thermal profile is for the crust in that area, how deep you have to get before it’s too ductile for EQs.

          But, if there was magma movement at depth, I would expect at least a few tiny deeper quakes even if it is mostly too hot.

          • I have been digging up some information on Askja and was attended by Carls writings on this paper:

            Soosalu at all. found in 2006 and 2007 100plus “unexpected” (as they write) quakes, “lower crustal events” under Askja between 10 and 30 km depth. <M 1,5.

            So. Does IMO catch every deep signal? No.
            The current swarm covers 10km nearly up to the crust surface.
            I guess it takes more to erupt, but this swarm could be another sign in the current run up.

            Another thing stands up. The ax of this swarm doesn't follow the main direction nne ssw of dykes and cracks but seems to curve a bit around the outter boundary of Aksja.

        • (Source IMO)
          An earthquake swarm started the 7th of November just east of Askja volcano and is still ongoing. Around 700 earthquakes have been recorded in the area since the swarm started. The largest earthquake was about M3.4 and occurred on the 9th of November. In addition to that earthquake, one earthquake > M3.0 has been detected during the swarm until now. No volcanic tremor has been detected in the area. This is more like brittle type tectonic earthquakes related to continental drift. Earthquake swarms occur regularly around Herðubreið and Askja. The IMO is monitoring the activity 24/7.
          Written by a specialist at 12 Nov 17:11 GMT

        • The strange thing here is that so many quakes are located within a few km3 rock volume. It should all be severely fractured by now. So, if it is not a dragon refurnishing its denn, what is it? Still tectonic like dry drumplots.

          • You can get this if the static friction and dynamic fraction are almost the same. Stress tries to move the fault, and static friction keeps it in place. Once the stress gets too large, the fault (or a small part of the fault) starts moving. Now dynamic friction counters the movement but this is less than the static friction so things keep moving. It stops when enough stress has been removed that the force drops below the dynamic friction. If static and dynamic friction are almost the same, then the fault will move very little and end up with almost the same stress as before. The movement puts a tad more stress on the neighbouring section which can do the same thing. Dynamic friction can be high in dry, brittle rock. But it can also be that the static friction is lower than usual, for instance because some water got in.

            An M1 quake at 5km depth would perhaps corresponds to an area of the fault of 30 by 30 meters. The M3.4 is by far the biggest mover and shaker and can have ruptured an area of 500 by 500 meters. Don’t quote me on these numbers: they are model-dependent ballpark figures. IMO will have a better idea. But it shows that there is plenty of room in the fault for such a swarm.

            The angle between the compression and the fault is important. That may be why the swarm forms a linear sequence.

          • IMO, as posted above state tectonic, as do those on here that have way more knowledge than me. But a couple of questions if i may

            One – there are some deeper quakes >10km and 1 a couple of hrs ago >17km so are all the EQ’s tectonic?

            Two – Can significant tectonic activity lead immediately to magmatic intrusion? I.e – chicken & egg – what comes first – breaking of rock allowing magma to intrude or magmatic pressure breaking the rock?

            PS – another excellent article Albert

          • Swebby, please see my reply below.
            This swarm is tectonic but it opens the space for magma to intrude.

            Hence, an eruption is definitively not out of question. And I think this swarm is making a small eruption at Askja, very likely.

  14. If I swallow liquid mercury… it just passes through my guts right?
    But the fumes are probably the issue when you swallowed it and its inside the bodys muscus membranes.
    I have heard of liquid mercury ingestion is not deadly at all?

    Is my opinons here correct?: I remeber learning this as a small child.

  15. Ref Minimata disease from Wikipedia;

    “While cat, dog, pig, and human deaths continued for 36 years, the government and company did little to prevent the pollution. The animal effects were severe enough in cats that they came to be named as having “dancing cat fever”.”

  16. This is my current take on the Askja swarm.

    In a nutshell.
    – What we are seeing here is a follow-up of Holuhraun.
    – The swarm is tectonic (earthquakes have a dry signature) and cover 3-10km.
    – During Holuhraun, about 50km long of rifting happened north of Bardarbunga, with the two plates moving apart about 0.5 meter in each direction. My figures are only approximate, not exact.
    – This rifting caused severe strain in the immediate adjacent tectonic boundaries, as they did not pulled apart as the rest. This includes the region south of Bardarbunga (Hamarinn) and the region north of Holuhraun (Askja).
    – This is the consequence. The strain is being released as a few kms of the upper crust are ripping apart too. The lower depths are still ductile, due to the massive event of 1875.
    – What happens next? As the crust opens apart, this create space for magma to fill the gaps or erupt. An eruption might happen sometime in the future.

    More concerning is probably the region south of Bardarbunga. Askja rifted in 1875, but Veidivotn rifted in 1477, so the accumulate strain is largest there. This means if we see an eruption starting at Askja, it will be a small fissure eruption, like in 1961. But the dead zone has more the habit of erupting less often and having large volume of eruptive magma, when it does.

    Alternatively, we could see the southern region being rifted not at Hamarinn-Veidivotn, but instead at Grimsvotn-Thordarhyma.

    • You are not considering Trollagigar in there, the fissure swarm south of Bardarbunga released strain with Trollagigar 1862. Askja had the huge rifting of 1875 north of it and a smaller rifting in 1924 with Þorvaldshraun to the south.

      An eruption like 1961 occurs in the ring fault as the caldera floor is lifted like a trapdoor and magma intrudes though the part that opens, it requires high pressure in the magma chamber of Askja and it isn’t caused by spreading.

      And regarding the swarm as an answer to Swebby aswell, the earthquakes seem to be tectonic, IMO confirms this and what James Farrell says about this being strike slip faulting seems likely. For the earthquakes to have some impact on the volcano they would have to be much more powerfull. Hawaii is in a diferent setting but it can work as an example, the earthquakes along the basal decollement create tensile stress along the rift zones so they can cause eruptions but you need to get to at least a M ~6.5 to cause some effect. Most do not, but there are two recorded examples of about this size that started intrusive processes lasting several months before the eruption. The 2 strongest Hawaiian eathquakes recorded: a M 7.7 and a M 7.9 triggered eruptions within a few hours. To have tectonic earthquakes that directly trigger eruptions you need large magnitudes >6.5, proximity to volcanoes (that are more or less prepared to erupt) and they have to affect the stress field in a very particular way.

  17. Based on the reasoning of my last comment (at 15:01), I decided to write this “How likely is it to see an eruption or major earthquake at each volcanic region in Iceland”

    Tjornes – last major tectonic episodes in 1934, 1963 and 1976 (based on its pattern, Tjornes might be due to another M6 earthquake)

    Between Krafla and Tjornes. This region, sandwiched between two areas that have recently experienced strain release, probably has a lot of strain accumulated. When it does, we will see a large magmatic event.

    Krafla: region experienced a major rifting episode in the 1980s. Nothing expected in soon.

    Between Askja and Krafla, and Askja itself: region experienced a major rifting episode in 1875. Because of recent events to the south at Holuhraun, there is a change of a minor eruption happening here in the near future. The start would be explosive, like a VEI2. But nothing big is expected.

    Between Askja and Bardarbunga/Grimsvotn. Holuhraun was the last major rifting episode here. The region will be dormant in decades to follow.

    Bardarbunga and Grimsvotn: I do not expect anything major at these two volcanoes, because of what happened during Holuhraun. But short lived explosive VEI4 eruptions are possible, especially considering the intrusion at Greip.

    Southwest of those volcanoes (Hamarinn and Thordarhyma): last major eruptions on these volcanoes were about 100 years ago. It is highly likely to see another explosive eruption at either of these volcanoes, which could be quite sizeable.

    Dead Zone: last major episodes in 1477 and 1783. Another major episode is likely sometime towards the end of this century. I see the possibility of a medium sized event in soon too (about 2-3km3), but no one knows how likely it would be.

    Hekla/Katla: the region has seen a fair share of events in recent decades. I wouldn’t be surprised to see Hekla going dormant for a long period, as well as Katla. If Katla erupts it will do a small VEI5 eruption. If Hekla erupts, it is going to be larger than the more recent eruptions.

    South Iceland Seismic Zone – last major tectonic episode in 2000 (another big event here rather unlikely). But earthquakes up to M5.5 are likely.

    Hengill: the region seems to be considerably ripe for another major event here, be a rifting event or a major earthquake. Last rifting event was around the time of Laki, and nearly triggered an eruption. The area was starved of magma back then apparently.

    Reykjanes and Krisuvik: I expect an eruption here to be very likely in the years ahead. Last events have been quite a while ago. Reykjanes erupted earlier last century and it does erupt quite regularly. Eruptions can be quite explosively due to proximity to the ocean.

    Between Hengill to Langjokull: Because this area is slowly dying down, most of the rifting has been performed by Vatnajokull and the dead zone, rather than this region. Last major event was about 1000 years ago. No one knows when the region is going to be reactivated again. But if it does, an eruption could be relatively likely to occur and be largely effusive.

    • Yes, and no sign of magmatic intrusions during the swarm… However some interesting GPS elevation..

    • As expected. I believe this swarm came from some compression on the fault, rather than rifting. Pressure from Askja. Pahala, on the other hand, is really going for it.

      • In previous eruptions at Askja, the eruptions came after a period of several weeks of earthquakes, which might have been like what we are seeing now. Days before the eruption, geothermal energy appeared in the area. This hasn’t happened yet.

        But we are seeing quakes down to 8km and ocasionally 10km deep.
        At around 12km deep, its probably magma, so as the swarm gets deeper, the changes for an accidental eruption increases.

        I still think this might result in an eruption in a few weeks or months from now.

        A very different setting, but Eyjafjalljokull also erupted after many weeks of mild swarms. They started in late 2009, 3 months before the eruption.

  18. Source(IMO)

    Specialist remark:
    The seismic activity east of Askja, that began on November 7th, has been decreasing since wednesday night (13.11) but it is still not over. Around 1200 earthquakes have been recorded in the area since the swarm started, with three earthquakes larger than M3. No volcanic tremor has been detected in the area and no deformation is currently ongoing. This swarm is likely due to tectonic activity. Earthquake swarms occur regularly around Herðubreið and Askja, however the current activity is so far, the largest swarm measured in this area. IMO is monitoring the activity 24/7.
    Written by a specialist at 15 Nov 01:00 GMT

    • I think a reaction to the stress change caused by the Askja quake swarm. Sort of adjustment.

      Striking signal at Thorvaldshraun.
      Maybe weather related, nothing at Askja SIL station.

      Graph by IMO.

  19. I was looking at the and notice during around mid 2015 on the Askja plot . A large number of quakes in the same area as this recent swarm. I feel this is connected with herdubreid

    • There’s a lab bench picture at the link and if you zoom in an expiry date looks a little strange…

      • Good catch. But it doesn’t matter. The ingredient is stable for decades, even if the label indicates otherwise. Bacterial contamination is the main reason for the expiry date. If the electrodes are properly calibrated, the accuracy of the results will not be affected.

        • Agree. the solution is stable for centuries if sterile and not opened to let in bugs.

    • These results are very interesting. The lake is not as acidic as many of us thought. A pH of 4 makes it even less acidic than a coke drink. Of course it might still be harmful because of other ingredients (especially metal ions) but as a chemist I‘ve seen worse cocktails than that. 😉

  20. 6 stars just appeared in Iceland

    16.11.2019 12:20:19 63.605 -23.396 1.3 km 3.0 90.02 9.8 km SSW of Geirfugladrangur
    16.11.2019 12:19:02 63.669 -23.599 12.5 km 3.7 73.31 15.4 km W of Geirfugladrangur
    16.11.2019 12:15:23 63.590 -23.640 4.2 km 3.5 50.5 13.8 km NE of Eldeyjarboði
    16.11.2019 12:14:19 63.828 -22.909 11.0 km 3.0 90.03 10.0 km NNE of Eldey
    16.11.2019 12:12:53 63.642 -23.546 12.4 km 3.4 90.01 13.4 km WSW of Geirfugladrangur
    16.11.2019 12:11:55 63.664 -23.487 0.1 km 3.1 99.0 10.0 km W of Geirfugladrangur

    • And ongoing

      Reykjanes ridge – earthquakes during the last 48 hours
      (Preliminary results)

      Earthquake count:

      Magnitude less than 1 in all: 8
      Magnitude 1 to 2 in all: 9
      Magnitude 2 to 3 in all: 17
      Magnitude more than 3 in all: 12
      Total: 46

    • Searching back this seems to be one of the largest swarms in that spot since 2015

      Today (01-July-2015) earthquake activity continued on the Reykjanes ridge, largest earthquakes so far are magnitude 5,0 (EMSC information here). Second largest earthquake had magnitude 4,8, other earthquakes have been smaller in magnitude. Total of 35 earthquakes that have taken place are larger than magnitude 3,0 and total number of earthquakes when this is written is 537.

      That swarm started with 2s and 3s then built up. IMO also raised the Aviation code to Yellow for Eldey at that time.

    • EMSC and USGS had this as a 4 and IMO now agrees

      16.11.2019 13:17:50 63.685 -23.591 2.2 km 4.4 99.0 15.0 km W of Geirfugladrangur

  21. Source:(IMO)

    Specialist remark

    An earthquake swarm started this morning on Reykjanes ridge, around noon few earthquakes > M3.0 were detected. The largest earthquakes of swarm was M4.5 at 13:17. The swarm is located 45 km SW of Reykjanes. Tens of smaller earthquakes have been detected since noon and the swarm continues. The IMO has received reports of the earthquakes being felt in Reykjanes peninsula, the capital area and Akranes. Earthquakes of similar magnitude were last recorded in June 2018 and an intense swarm occurred in the same area in June and July 2015, then the largest earthquakes was M5.0
    Written by a specialist at 16 Nov 14:32 GMT

  22. Wow!
    This afternoon 26 stars in Reykjanes swarm. Largest quake was a M4.5 at 2km deep. Many quakes are quite deep.

    This is swarm that surely can result in an eruption, if one it’s not already happening. Haven’t had a chance to look at the tremor graphs. However a similar swarm happened in 2015. Not sure how this one compares with that former one.

    The fact that depth goes between 2km and 22km tells me that this is more of a tectonic-magmatic swarm rather than a purely tectonic event.

    An eventual eruption would be explosive (even up to VEI4), could be Surtsey-like, or purely underwater.

    • I wonder if this swarm could complicate the detection of minor quakes at Askja…

      • I actually thought Askja erupted a few days ago when I saw this appear 🙂

        Volcanic Ash Advisory from London

        DTG: 20191108/1418Z
        VAAC: LONDON
        VOLCANO: ASKJA 3730-60
        PSN: N6503 W01678
        SUMMIT ELEV: 3643M
        ADVISORY NR: 2019/001
        OBS VA DTG: 08/1418Z
        FCST VA CLD +6HR: 08/2018Z NO VA EXP
        FCST VA CLD +12HR: 09/0218Z NO VA EXP
        FCST VA CLD +18HR: 09/0818Z NO VA EXP

        NXT ADVISORY: WILL BE ISSUED BY 20191108/1600Z

        • They are really on top of it.

          I guess they will be doing an exercise on Reykjanes eruption next week. Lol

    • The Reykjanes swarm seems to stop now
      But more can happen too

    • At Jón Frímann’s blog there’s an archive of the first day of activity in 2015

      And here’s where we are up to now in 2019

      IMO updated the commentary to add “an intense swarm occurred in the same area in June and July 2015, then the largest earthquakes was M5.0 and seven earthquakes > M4.0.”

      So quite a way to go yet to match that.

        • Not easy to give a comment when it get redacted… (!)

          I wrote something like; The main difference between the 2015 and todays swarm seems to be the lack of smaller than (<) 2,0 eq's in todays swarm. Due to weather? Instruments? Or…? Of 199 eq's from 05.48 today and going on for 15 hours only 29 were smaller than (<) 2,0.

          This became "The main difference seems to be the lack of eq’s 2,0. Any thoughts?"

          Someone drinking in the dungeon tonight? 😀

          • I blame the cookies. They must have gone off with the missing text. This is what was found in the dungeon.

          • I had a quick look. The comment arrived in the system in its brief form. It was quarantined for reasons I don’t know (the system has an automatic decision tree but it is not always clear to us what it actually does), and released by manual intervention. But it wasn’t edited – honest!

  23. Thanks Albert for a fine essay which makes this mercury chemist and occasional VC visitor glad! Organomercury compounds were a part of my PhD thesis many years ago.

    My comment is actually about fluorine, not mercury. One of the features of the Laki eruption in 1783 was a vast emission of fluorine, mainly as HF. That was a large basaltic eruption. The result was most of the livestock on Iceland at the time died of fluorosis upon ingesting massive amounts of fluoride during grazing. Something like a quarter of the human population of Iceland perished too.

    So I suspect one of the features of the basaltic LIPs events would be gigantic effusions of hydrogen fluoride as well as the other volcanic gases. On the basis of the Laki eruption I suspect the consequences of all that fluoride would be worse than the mercury.

    This was briefly held in the ‘for approval’ queue, as is done for all first-time commenters. Future comments should appear instantly. -admin

    • Thank you for the nice comment. Fluorine seems to have had little attention in the past decade. The amount of fluorine in the early Siberian Trap magma was similar to the amount of sulfur. The halogens are clearly important. It it gets into the stratosphere there might be ozone consequences as well. The dispersion in Iceland seems related to the ash rather than the gas, and if this is general it could limit worldwide impacts. How is fluorine dispersed?

      • Albert – Seems mainly to be in the form of volatile HF. If it is HF, or hydrofluoric acid, then it rains out like SO2. Then it will react with alkaline minerals and remain in the soil, often as calcium fluoride or calcium fluorapatite.

        Also if there is a lot of sodium in the magma there would be NaF as well, which has some volatility at high temperature. It might be concentrated in ash moreso than in lava.

        So I suspect the fluorosis issue would dissipate over a few months or years as soluble fluoride salts are washed out or converted to insoluble ones like the fluorapatite.

        In a big flood basalt eruption though you’d probably get continued replenishment of the gaseous HF and soluble salts in soil. Which might be an issue for terrestrial grazing animals possibly over a very wide area.

        I’m no expert on fluorine and volcanic eruptions, just that I’ve seen mention of the fluorosis problem in the write ups on Laki. IMO also warns farmers of the issue in Iceland when an eruption is occurring.

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