Awkward but promising: Compromise paper from Andronikov & Van Hoesel

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The presence of a possible meteoritic component in the same sediments suggests that an ET event occurred at approximately the same time. However, whether the presence of the meteoritic component is due to a local meteorite impact/airburst or to a much stronger event remains unclear. Anyway, it is quite possible that some short and dramatic event took place just before the onset of the Younger Dryas climate oscillation, but, as was emphasized by Haynes et al. (2010), an understanding of what happened at c. 12.9– 12.8 ka BP requires further research.

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  • carol smith

    That is an important admission – an ET event sparked a local volcanic outburst sparked widespread evidence of landscape fires. What’s not to like?

  • George Howard

    Does anyone at CT read the papers any longer? This post is chock full of comment worthy material!

  • I read it. I occasionally drop in here and I appreciate your posting of the PDF. One of Ander’s Carlson’s PHD student did a thesis on the continental ice sheet discharge and claim definitively that the Champlain Sea and the St; Lawrence were active discharge routes at 13K BP and the Arctic route was active around 12.4 PB, which combined with sea ice and atmospheric feedbacks are sufficient to explain the timing and duration of the Younger Dryas reversal. That will certainly be contested but the Arctic first crowd seems to be backing off from that a bit.

    OSIRIS-REx is on the way to Bennu, which appears to be a circularized and cooked out version of the highly elliptical examples of the kind of carbon rich impactors of the size that are required to be dangerous to Earth in the short term. So there is and will be some near term progress there. I find it interesting that Andronikov’s collaborators have continued to take an interest in this, sedimentary nanascale particle paloehistory of impactors still has a way to go, and the sedimentary nanodiamond results still need to be better characterized.

    I don’t hold out much hope for the Black Sturgeon River hypothesis, but there still could be some surprises there. This is interesting work but certainly not definitive. I’m really not interested in the other discussions here.

  • George Howard

    Thanks, TLE!

  • Thanks again for posting the pdf, George, that really makes it happen for me. Otherwise I would not get to it for months. Keep up the good work! I don’t mind the side discussions, I just don’t follow them much anymore. This is the only blog I am aware of that deals exclusively with impacts and such.

  • Trent Telenko

    There is that Meteor & Volcano pattern again.

    It seems to show up with every major boloid impact event.

  • I would suggest that the meteor – volcano pattern may be a bit misleading. The volcanic activity is for all intents and purposes continuous, though the intensity tends to wax and wane a bit over time. The larger the eruptions are, the less frequent they are but the overall coverage is essentially worldwide.

    For instance, around the same time as the Y-D impact, the Laacher See (VEI 6) erupted in Germany and Campi Flegri created a small caldera (at least VEI 4) in the Naples area. Both eruptions are close enough to thoroughly dust the Netherlands depending on which direction the prevailing winds are blowing. Cheers –

  • I have no problem believing that impacts can instigate eruptions and movements of faults. Take for example windshield starring, if the vehicle is left static in a garage it is unlikely to change, but if you drive it over rough roads it is likely to propagate the cracks across the windshield. It would seem to be a given if not fact. Alike the new 30 ton meteorite in Argentina, it had to shake the local area somewhat. The ancient legends of the Old and New World tell of the Higher Power shattering the world similar to casting pottery to the ground producing massive earthquakes and floods which would be expected from a comet slamming into the Laurentide Ice Sheet, to say that such reverberation globally wouldn’t effect volcanic hot spots is just plain denial.

    As for Campi Flegri, the seat of the Cumaean Sibyl who prognosticated future catastrophes or spin doctoring from past actualities, and the Minoan eruption are to be expected when the water from the sea level rise started flooding through the Pillars of Hercules and filling up the Mediterranean Sea Valley.

  • Paul Repstock

    Bard: There is a “much” larger feature which I believe is a volcanic result of an impact. So far as I can determine, the timing is impeccable.

  • Casual visitor

    The paper is a bit misleading, as it states that the year of eruption was 12,880 BP, which is incorrect. If one follows the references from the paper, one can find out that the actual time interval is 12,880-12,920 BP, because of the unknown number of missing varves. Other studies put this date more closer to the earlier value, which is before the YDB impact event at 12,900 BP.

    However, Petaev’s Greenland data point to a *minor* peak of Pt a decade earlier. This is the impact that coincides with the Laacher See tephra.

    Whether an impact caused the eruption, or if they are merely coincidental, can not be concluded from this paper.

    I can also say that the data in tables is not ordered by age, which makes the paper very obfuscated for reading.
    Nonetheless, it’s a good one.

  • Just saw the my first fireball! About six times bigger than Mars and the same color with a long tail maybe four times the width of the galaxy. Paul – Where? Impact and volcanic in the same place, sounds extremely hard to substantiate. Found something of Face Book called Younger Dryas Comet.

  • Paul Repstock

    No Bard, not hard to substantiate (or dispute) if you have enough computer power. This “Impact and the Volcanic activity” were actually on opposite sides of the Earth. The Volcanic activity was the eruption of the Deccan Plateau…And the Bolide/Impact was …Chicxulub…
    The eruption of the “Deccan Traps” was for a long time theorized as the cause of the Dinosaur extinction; until the discovery of Chicxulub.
    The time frame fits both. The impact crater was deep enough to allow the energy to transfer to the molten layers of the Earth, where I theorize it was dispersed radially till the shock wave met on the opposite side of the planet and erupted(very long string of question marks)???
    Note that there are other Shield Volcanos which are hard to explain (although perpendicular impacts like Chicxulub must have been rare).

  • Casual visitor

    A volcano erupts with a pyroclastic explosion when there are enough pressure from the trapped gases below to break the thin crust over them.

    But, if a comet impacts directly on volcano, with a sufficient force to break the crust, volatiles from the comet would evaporate and provide steam for the explosion.

    In case of the Laacher See, a small cometary impactor of about 300 meters in diameter would do the trick.

    Alternatively, a much larger object impacted elsewhere, created an earthquake, and surely left a crater, which is … nowhere to be found.

    So, logic says that the Laacher See is an impact crater, superimposed on a volcano. An unlikely, but quite possible impact event.

    To substantiate this claim, aside from finding the extraterrestrial material in the tephra layer, which this paper did, one also has to look on the pattern of the initial tephra distribution. In Laacher See case, it has a butterfly shape, typically resulting from an impact.

    Is this enough of evidence, or should I add some more ?

  • Paul Repstock

    Casual: There is nothing wrong with Theorizing or even Speculating. Please provide any evidence you can think of. The span of Human civilization is so brief we have little historical “Evidence” and much of what we have has been obscured by bias and tampering.

  • Casual visitor

    The crater is NE-SW oriented, which implies an impactor from that direction, if it was an impact. The plume from an impact always goes backward, following the path of impactor, which in this case was decidedly to NE. This is a further corroboration that the eruption was triggered by an impact. By the way, I am not speculating, I am simply commenting on the paper. This paper by itself is not a sufficient evidence for anything, which is also a conclusion of the authors, but it provides a finding, which can be matched with clues from other papers.

    For me, this is enough of evidence to conclude that the Laacher See eruption was most likely triggered by an impact of a small cometary chunk directly at volcano.

    ‘Most likely’ means that this is the only viable option left on the table that checks all the evidence.

    The sufficient evidence to prove this scenario is distribution of ejecta in a pattern expected from an impact; orientation and shape of the crater that matches with the observed distribution; presence of extraterrestrial material in the tephra on a wide area, including Greenland cores.

    Can you think of an alternative scenario that checks all the evidence ?

  • Hermann Burchard

    @Casual: The issue of volcanism from an impact has gummed up for the last 13 years by this paper:

    Ivanov B A & Melosh H J (2003), Impacts do not initiate volcanic eruptions:
    eruptions close to the crater. Geology 31, 869-872.

    The authors are ignoring the volatiles dissolved in the mantle, “trapped gases below,” as you mention. The importance of such has been recognized only in recent decades, largely due to Stephen Sparks, who has won several prestigious awards, including the 2015 Vetlesen prize, LDEO, Columbia Univ, the “Nobel prize of the Earth Sciences.” Sparks explains the lower solidus (~liquidus, melting temperature):

    Sparks R S J (2003), Dynamics of magma degassing, in: Oppenheimer C, Pyle D
    M, Barclay J, eds., Volcanic degassing. The Geological Society, London
    2003),

    quoting:

    Degassing has profound effects on the phase equilibria of magmas, because rather small amounts of water dissolved in magmas can reduce their liquidus temperature by hundreds of degrees. Conversely, degassing can cause
    spontaneous crystallization. While these effects have been known about for many decades, it is only relatively recently that their significance for understanding volcanic processes had been widely appreciated.

    Based on this, impact volcanism seems plausibly caused when the volatiles come out of solution in the impact.

  • CV – interesting suggestion. At the link is a depiction of the the butterfly shape of the LS tephras. I count at least 7 different units. And the depth appears to be significantly deeper to the north than the south. Looks like the winds were highly variable during the series of eruptions. There is even a lobe to the SW of the crater.

    Had this been triggered by an impact and the major blast taken place at the same time, you would have depths based on the prevailing winds and roughly equal distributions north and south of the crater for the heavy stuff / thick stuff, which I don’t see.

    http://hercolano2.blogspot.com/2012/10/youngest-dryas-age-vulcanism-in-central.html

    The farther you get away from the crater, the thinner the tephras are – measured at less than half a cm for most of the southern lobe. As this eruption and the YD impact were very close in time, I think you get good mixing of both types of debris, especially farther from the vent.

    While you can certainly make a case that an impact caused the eruption, I don’t know that we have seen anything like that ever and am not prepared to board that particular bus (yet).

    Alternative explanation? Very close in time impact in Michigan for the YD body and a large eruption out of the LS. Don’t see a need to invoke a direct hit at this time but sure would like to see what else you have on this. Cheers –

  • Hermann Burchard

    agimarc: In impact volcanism, we expect a delay between the impact explosion and subsequent “recurrent” volcanism. The time lapse comes from volatiles seeping into the impact cavity, refilled after collapse of the original blast hole, which may have been as deep as 1/10 -1/3 of diameter. In the Yellowstone case, suspected to be from a lower Miocene impact in the Modoc plateau, NE California, early intervals were 40ka, now 600ka. Impact volcanism occurs only if the impact was thin crust. The Laacher See is in the volcanic Eifel which is thin crust.

  • Casual visitor

    Perhaps you missed that the volatiles that I was talking about are those from the comet. A comet is essentially alll made of water, CO2 and CO ices, with some solid material in addition.

    Based on the crater size, I estimate that the impactor was a roughly 300 m in size, almost certainly not round.

    The impactor of that size was capable of penetrating the thin crust at Laacher See. Then the volatiles of the comet would be injected by the momentum of the impactor into the liquid lava below the thin crust. split second later the ices, now mixed with molten lava, are stopped in their track and turn into vapor. Then everything explodes.

    Subsequent earthquakes and turmoil prolong the eruption for several days. Whatever was trapped below escapes, now that the path was open.

    Initial tephra goes primarily to the plume that went back to the path of impactor, to NE. Subsequent layers of tephra might have more regular distribution that can mask the initial distribution to some extent.

    Prevailing winds in Europe now at spring time of year are west-east, not at all to NE. Back then was an Ice Age, so the wind pattern could have been a bit different. I am not an expert on weather.

    Laacher See ejected 6 cubic km of tephra. If the impactor was a 300 meters comet, then it would have brought in about 0.014 cubic km of material, which turned out on impact into 10-14 cubic kilometers of gases.

    An impact by an asteroid would not make such a blast and would leave much more ET material around, so I can conclude that the impactor was a chunk of a comet, of the same one that impacted the LIS a decade later.

    If you think that the impact in Michigan in 12,900 BP was the only impact at that time, then please explain the existence of two peaks of Pt in Greenland data, clearly separated by a decade ? What caused the very clearly pronounced minor peak of Pt ? This is why you need the additional impactor at Laacher See.

    Furthermore, the dating of Laacher See puts it with high confidence to that time, a decade earlier.

    Yes, I agree that the event is an odd hit, but unless it happened, you would have the problem to explain the ice data of Petaev.

    Remember SL9: a comet passed by Jupiter and came back to hit on the subsequent pass. My opinion, a comet passed by Earth, hit Laacher See with a minor chunk and came back later to impact at 12,900 BP. One decade of a discrepancy time makes it a Jupiter family comet, which is consistent with it being a strayed Centaur.

    Anyway, I’ll add one more argument to the pile: the hunter-gatherers in the area immediately after the event switched from using 80% bow&arrows, 20% spears to 20% bow&arrows, 80% spears.
    (I can name the paper of that study if you ask me.)
    The authors thought that the eruption traumatized them enough to lose the wisdom of making bows and arrows, but I say that they switched to using more spears when they saw gods using spear too. The impactor resembled spear.

  • Paul Repstock

    Casual; Technology is fragile and the making of “effective” bows and arrows is not as simple as you might think. I appreciate your information, but I think that people are easily traumatized.
    Imagine what would happen to our present “civilization” in the event of a major impact. Even if half the Earth’s population survived, I suspect that within a generation, there would be nobody available who could program a computer. Catastrophies are “Paradigm Shifts”. They can make old technology irrelevant.

  • Howdy CV –

    The physics of a grey eruption is similar to that of shaking up a bottle of champagne or beer and popping the top. The volatiles are part of the magma, as they depressurize they propel the magma upward. During the height of the depressurization, the eruption column goes straight up – a Plinian eruption. As the erupting magma degasses, the column collapses into pyroclastic flows / density currents. At a microscopic level, the particles are essentially frothed glass. The LS eruption has been described as phreatomagmatic – essentially driven by magma interaction with the water table. This normally blows large circular holes in the surface called maars.

    http://lib.ugent.be/fulltxt/RUG01/001/892/503/RUG01-001892503_2012_0001_AC.pdf

    I don’t think you need the injection of .01 km3 of water from an external source to drive this particular eruption.

    In this, I am only focusing on LS and don’t want to discuss the rest of the YD. As I understand the festivities, the central area of impact was somewhere in upper Michigan. I tend to agree with Dennis Cox that what he calls a comet storm fried North America during the YD encounter.

    Here is a thought experiment. Assume North America got nailed with a comet storm with multiple small caliber impacts and airbursts. Dennis Cox identified what he believes to be multiple small craters in west Texas and farther west. At that same time, there was basaltic magmas close to the surface very close to west Texas in NM – the Clayton – Raton volcano field is an example. Yet we see no evidence of an impact caused Plinian eruptions in NM volcanism. Recent volcanic activity is almost exclusively basaltic in nature.

    I know there is a lot of arm waving with the above. It is simply another way to say that we haven’t seen direct connections with small impacts and small scale volcanic eruptions. OTOH, we think there are connections between large impacts and large scale antipodal volcanism (Siberia / Deccan Traps). Some have made the case that many of the known hotspots are antipodal to or directly beneath large impact craters. But I know of nothing that connects small impact events (and this is what we have with the YD as we have no craters tens to hundreds of miles across associated with it) with single eruptions.

    http://www.mantleplumes.org/WebDocuments/Antip_hot.pdf

    Once again, I still don’t think you have to invoke an impact with LS. Still looking for more. So like what else do you have? Cheers –

  • Paul Repstock

    Thanks for the link Agimarc. I skimmed the first bit and filed for latter study.
    Are you suggesting that the idea I posted above is invalidated by the “Mantle Plumes” article? The first thing which occurs to me, is that there is no Hotspot below the Chicxlub Crater?

  • Casual visitor

    The Petaev’s Pt data from Greenland ice cores has two spikes. *Please explain the presence of the minor peak without the impact at LS* ?

    agimarc:’we haven’t seen a direct connection between seen direct connections with small impacts and small scale volcanic eruptions’. The chances for the occurrence of such impacts is 1/50,000, one order of magnitude more or less. This is based on a surface area of volcanoes divided with the surface area of Earth. LS is thus a very rare event, if impact based. Nobody clearly ruled that out because nobody checked.
    Nobody proved that ‘water table’ was not the water from the cometary impactor.

    This was not envisioned as a ‘small caliber event’, but as a hit with a 300 m body. Please stick to the scenario.

    If you wish to rule it out, explain the minor peak of Pt.

    Regarding bow&arrows, they did not lost it, just used the technology less often, or their arrow tips became atypically spear-like.
    (Src: “The Laacher See-eruption (12,920 BP) and
    material culture change at the end of the Allerød in Northern Europe” by F. Riede)
    At the said paper look at the picture one to see a butterfly shape of tephra around the crater. The great plume went NE, as expected from an impact from that direction, and was shifted sideways to east by the prevailing W->E winds before it fell. There are also deposits to SE, equally wide, but thin, of <1 cm depth, which is 10% of the initial plume volume. This distribution corroborates the impact initiation of LS.

    Can you explain why the plume went primarily to NE if the seasonal winds do not blow that way ? The plume *did not* went straight up. Please stick to the facts.

    As for trauma, yes surely. There is a whole network of underground tunnels in Europe, stretching from Scotland to Turkey, of prehistoric age and unknown use. I reckon that they built it because they feared that the sky might fall upon their heads, because they saw something horrifying…
    a large comet in low flight. Otherwise, they are pretty much inexplicable, because there is no civilization associated with them.

  • Paul Repstock

    >”As for trauma, yes surely. There is a whole network of underground tunnels in Europe, stretching from Scotland to Turkey”<
    That is amazing! I had no idea of this. Could you please provide links?
    Thank You
    Paul

  • Hermann Burchard

    Paul R., “. . no Hotspot below the Chicxlub Crater?”

    IMHO, the impactor only penetrated to the Moho, making a Moho “warmspot” & plutonism, not a mantle hotspot & no volcanism. Northern Yucatan and the Greater Antilles are Cretaceous limestone underlain by plutons pushed up from the Moho warmspot, East to Virgin Gorda with its famous plutonic Baths. After that, the warmspot joined Lesser Antilles volcanics.

  • Casual visitor

    Paul, just google ‘tunnels Turkey Scotland’ and bingo.
    The tunnels are over 12ka old.

    George, could you please start a separate thread with the Laacher See document suggested earlier by agimarc ? It is a treasure trove of information.
    Thank you.

  • Hermann Burchard

    @ Casual V., “Perhaps you missed that the volatiles that I was talking about are those from the comet.”

    Sorry for my oversight. Actually, my volatiles were your “trapped gases:”

    “A volcano erupts with a pyroclastic explosion when there are enough pressure from the trapped gases below to break the thin crust over them.”

    BTW, I had been hoping to get some comments about my amateurish remarks explaining the Greater Antilles as caused by plutonism related to Chicxulub.

    I have mentioned this on Tusk & CCNet for the last 15 years or so with no response from any actual geoscientists.

  • Howdy CV –

    Please provide a link to Petaev’s data from Greenland and explain why it is relevant. Note that ice core spikes are notoriously difficult to characterize. The 535 – 539 AD spikes were only recently determined to be a pair of volcanic eruptions by Jonny and Baillie who are the resident experts on tree ring data.

    But if LS is impact based, then cometary gas isotope ratios will show up in the tephra. As far as I can tell it doesn’t. Why not?

    I am not ruling out anything. Compared to Chesapeake / Popigai this is a small caliber event. I am looking for proof.

    Look closer at the drawing. The multiple lobes were the product of multiple eruptions – not a single eruption. Each one laid down debris downwind from the crater. There’s even a SW pointing lobe.

    I don’t care what the seasonal winds are today. All I know is where the tephra was distributed then. Looks to me like the wind changed, at least a couple times. Directed eruptions normally don’t deposit tephra. Rather, they deposit ignimbrites meters to tens to hundreds of meters thick. But those are normally relatively close to the vent rather than continent wide.

    You might want to familiarize yourself with maars – highly explosive surface eruptions with lots and lots of water interacting with the magma. LS is described as a maar which in my mind is sufficient explanation. Cheers –

    http://geology.com/stories/13/maar/

  • Casual visitor

    Hello agimarc, thank you very much for the link on Laacher See.

    Petaev paper: http://www.google.rs/url?q=https://faculty.unlv.edu/wpmu/shuang/files/2014/08/Petaev-et-al-2013.pdf&sa=U&ved=0ahUKEwjotLiGkrzPAhVhDsAKHaz3Bf8QFggsMAU&usg=AFQjCNEnn_1oGmBCcKUN1Mlth8mGZr8gJA

    Petaev’s supplemental information (very important):
    http://www.pnas.org/content/suppl/2013/07/17/1303924110.DCSupplemental/pnas.201303924SI.pdf

    Alternatively, Google ‘Petaev Platinum ice cores’.

    If you examine the high resolution supplemental data, you will find that there are two spikes of Pt, clearly extraterrestrial in origin. This means that there was a small impact one decade before the main one.

    Additional point to note is that the impactor had a very odd composition. I’ll leave the debate about that to some other post/time.

    I agree that it is a small event in comparison with Cheasapeake/Popigai, but was still a major disaster, large enogh to show in Greenland ice cores, I think as the first tephra layer, as marked in the paper that is being discussed in this thread.

    Anyway, I am still reading the Laacher See paper that you pointed earlier. I had no idea how unique the LSE was! If George puts it as a separate thread, I have an intention to comment on it extensively. In my view the supplied data scream all over the text: ‘impact, impact!’ I found a dozen corroborations on the first 20 pages alone. Amazing!

    I am familiar with the maars, but this is not a sufficient explanation.

    By the way, you cannot ignore the seasonal winds, if you wish to be objective.
    In my view, both NE & SW lobes were shifted lightly eastward, which is fully consistent with a scenario that the wind blew from west to east during the duration of eruption (estimated as three days).
    But, the presence of two lobes is consistent with the impact scenario, as well as the ratio of the amount of material in these lobes – the SW lobe is thinner by an order of magnitude.

    Finally, the eruption only started by an impact, but it then continued as a normal eruption for days, so it is an atypical combo of both processes. This clearly shows in the supplied data in the paper that you pointed out, if read very carefully, having in mind the triggering impact as an alternative explanation for the numerous observed uniquenesses & anomalies.

    I will refrain myself from further commenting until I finish reading the paper. I hope that George would decide to start a separate thread by then. That paper really deserves a separate debate on whether the data can be alternatively better explained as a result of an impact, or not. Cheers!

  • Howdy CV –

    Not trying to be overly obstinate. Still think if there was an external trigger, the off-world isotope mix would show up in the tephras at some level.

    http://www.hou.usra.edu/meetings/lpsc2015/pdf/2621.pdf

    https://e-reports-ext.llnl.gov/pdf/339631.pdf

    Maars and kimberlite pipes are somewhat odd ducks in the volcano world. Not sure that I understand either or both at any level than “kind of.”

    Many thanks for the links and additional reason for some head scratching. Cheers –

  • And if you’re going to be that way about it (tongue firmly in cheek), I look forward to my continuing education (or lack thereof). Cheers –

  • Casual visitor

    Hello agimarc.

    The ET isotope composition did show in the tephra. May I remind you that this is exactly the topic of this thread ? This is becoming hilarious.

    If you read carefully the paper that you suggested, you will find that the tephra composition is one of many oddities of the LSE.

    Bottom line: if LSE is not an ordinary event, but was triggered by an impact, it would be a unique case of a volcanic explosion on the record, which would show on many levels and parameters. This is exactly what was shown on the paper that you pointed out, over and over again, on almost every page. Hilarious stuff. It gave me the best laugh I had in this October! Thank you very much for the link. I would have never found it by myself. Cheers.

  • Jonny McAneney

    Casual Visitor,

    There is a weakness in your model for an impact as a precursor to the Laacher See eruption, and this lies in the linking of the dating of the Laacher See tephra to the Platinum Spike in Greenland Ice cores.

    Let us look at the age of the Pt spike in the GISP2 ice core. We see that the larger and smaller anomalies occurs between a depth of 1712 and 1712.5m, which one can find to correspond to an age of 12,883 to 12,897 ice years BP.

    Then when we look at the dating of the Laacher See eruption using varves, we get a date of 12,880 +/- 40 varve years BP. That on face value seems like a pretty decent match. There are two inherent problems though. The first is of course (as I have highlighted elsewhere on this site, and probably quite a few times), is that one is effectively trying to fit a single ice core date to a single event that occurred within an 80 year time frame.

    The second, and probably by far the more series one is that you are taking at face value that the ice core dates are correct. I can assure you that in absolute terms, the ice core dates are not correct. One can find amongst the suit of ice core data a file of tie dates between the GRIP ice core (dated using the GICC05 timescale) and the GISP2 ice core. Effectively the ice core workers have identified the same volcanic events in both ice cores, back to around 4000 ice years BP. The issue is that in these ice cores, by around 4000 BP, GISP2 is at least 30 years older than GRIP. But we also know that GRIP is at least 7 years older than real calendar dates before the 1st millennium AD (Baillie and McAneney 2015, Sigl et al (2015)). This implies that GISP2 dates are at least 37 years too old with respect to real time.

    But it gets much worse. There is a growing body of research that indicates the chronological offset between the GICC05 timescale and real time increases the deeper in the core one goes, amounting to around 70 years in the early Holocene and around the end of the Younger Dryas (see Torbenson et al 2015; Lohne et al 2013). That is the GICC05 timescale becomes increasingly offset from 7 years too old at 1000 BP, to 70 years by around 10,000 BP. I should point out though that these offsets are actually outside of the estimated counting errors. So there seems to be a trend that the ice core ages grow too old with respect to real calendar dates as one goes deeper in the core.

    Now, the end of the Younger Dryas was an abrupt affair, with temperatures recovering in as little as a decade. If we look to the ages of the end of the Younger Dryas in each ice core we find that GRIP gives it as 11,500 +/- 50 BP, and GISP2 11,640 +/- 280 ice years. Remember, these two cores were drilled 30 kilometres apart, so they are likely recording the same climatic conditions. Ignoring the uncertainties for a moment, we can see that GISP2 is 140 years older than GRIP, and we know that GRIP is at least 70 years too old by this time. This could imply that GISP2 could be as much as 210 years too old with respect to real calendar dates, by the end of the younger dryas. This is just ignoring the uncertainties; if we include the uncertainties then it becomes a lot more complex.

    It does look as if the GRIP core is a better chronology in relative dating than the GISP2 core. I don’t think anyone could argue otherwise on scientific grounds, especially since the GISP2 core is not a contiguous record, since it suffers from missing data due to sections of damaged ice during the extraction of the core. So let us then say for the sake of argument, and maximum optimism, that the end of the YD was 11,550 BP ice years, and thus the offset between GRIP and GISP2 is only 90 years, resulting in GISP2 being around 160 years too old with respect to real calendar dates.

    What this effectively means is that the Platinum anomalies in GISP2 are also 140 years too old, and so are probably around 12,720 – 12,730 BP give or take. The point now is that they are outside the 12,840-12,920 varve dating.

    The only true way though of linking the Pt anomaly to the Laacher See eruption though is to find Laacher See tephra in the same ice core layer as the platinum anomaly. Until this is done, then linking the Pt with Laacher See will remain a case of suck in and smear, and unprovable.

  • Hermann Burchard

    Jonny – “he Platinum anomalies in GISP2 are also 140 years too old, and so are probably around 12,720 – 12,730 BP give or take.”

    Are you saying there was a major ET incursion of the atmosphere during 12,720-12,730 BP, give or take??

    Just asking . .

  • Casual visitor

    Jonny Mc Aneney,

    So you are disputing the dates of ice records. This says nothing about whether the LSE was, or was not caused by an impact, disregarding of when it happened.

    I suggest that before we start arguing about *when* something has happened, we resolve *if* it has happened at all. For start, the topic of this thread was that the ET material was found in the layer that contains the LS tephra. That is one argument.

    The second argument that was raised by me was that the spatial distribution of tephra was what is expected from an impact, and requires awkward weather (epicycling) to explain it otherwise.

    Third, I pointed out that an impact into a volcano has a fairly low probability to happen. If it happened here, there would be tell-tale signs all over the eruption data. agimarc pointed to a paper that analyzes the eruption data in details. On many levels this eruption is very different from others in the record. This was not yet discussed.

    The point is that if you put into question whether the peak of Pt recorded in the cores is contemporary with the LSE, in order to try to
    refute the triggering impact hypothesis, then this is fine by me. there are plenty of other arguments. We might
    fully ignore the data from distant sites and focus on the crater of volcano itself.

    If you wish to question the validity of LSE being impact triggered, I suggest that we dissect the paper suggested by agimarc, about the LSE.
    All those uniqueness of the LSE have an alternative (impact caused)explanation that was never examined by the author of that paper. I have not finished reading it yet, so I will refrain from raising further arguments at this point, but until I do, you might also wish to address the other points already raised (ET material in the tephra and tephra distribution pattern).

    Finally, I take GISP2 cores as a reference dating point, and I have my reasons for trusting those dates the most, but it would be a widening of subject to discuss this here. This thread is about the ET material in the LS tephra, as collected locally, so I will keep my posts focused on debating that. If we come to a conclusion on *why* the observed ET material is in the tephra, then we might very well debate further on the dating of the LSE, the *when* question.

    By the way, the LS tephra was probably already found in the ice cores at the same layer. Look at the
    https://www.researchgate.net/profile/Achim_Brauer/publication/222965767_Lateglacial_calendar_year_chronology_based_on_annually_laminated_sediments_from_Lake_Meerfelder_Maar_Germany/links/54dddf9f0cf22a26721d1474.pdf, page 6. There are two layers of sulphur in ice cores, but it is uncertain which one (if any) is from the LSE. I admit that the authors have more reasons to believe that the older date is the LS tephra, in which case the whole GISP2 dating is erroneous, but I have my very scientifically based reasons, not stated here yet, to believe that the GISP2 dates are valid, so that the later T1 layer represents the LSE.

    Aneney: “Remember, these two cores were drilled 30 kilometres apart, so they are likely recording the same climatic conditions.”
    They most definitely do not. Look how strikingly different are the oxygen records from the YD period on the graph on page 6 from the paper above.

    By the way, it is not 12,880 +/- 40, but 12,880 – 12,920 interval. The 12,880 is based on how many varves they actually counted and is the latest possible date. They don’t know how many varves were lost in action, but they suspect that value to be very close to 30, or more precisely 30-40.

    Thus, the interval in question is really 40 years wide, whereby, if it is acknowledged that there are some varves missing in action, then the actual date is 12,910 – 12,920 BP, which is merely a decade (or two).

    Aneney: “We see that the larger and smaller anomalies occurs between a depth of 1712 and 1712.5m, which one can find to correspond to an age of 12,883 to 12,897 ice years BP.” This is incorrect reading. You have to look when the anomaly starts, which is below 1713,0 m, at the age around 12,912 BP. The dust ejected by imoact takes years to settle, which is why the peak occurs later. But please acknowledge that it goes from 0.078 to 1.05 at the interval around 12,912 BP. this is an increase by the factor 0f 13.5.

    Aneney: (see Torbenson et al 2015; Lohne et al 2013) This is not a proper reference unless you provide the full name of the paper, as stated in references (which we do not have here). Better yet, please provide web links if you wish to quote somebody.

  • CV –

    I need to be more precise. The phrase “in the tephra” has multiple meanings.

    For instance, we previously discussed particulate matter of the YD debris field mixed with the tephras. Particularly difficult to determine which came first in the portions of the field with light dusting. Perhaps not so difficult to determine in the thicker portions where layers can be mined and tested.

    What I am looking for are ET gasses in the actual vesicles inside the tephras. If this was an impact-caused event, we would see something different in tephras produced by the initial blast, especially if you are talking about a 300 m impactor. Still haven’t seen that yet. Will keep looking though. Cheers –

  • Jonny McAneney

    Hermann,

    I am not saying whether there was an Extraterrestrial incursion around 12,720-12,730 BP, give or take, for two reasons.

    1) I have no idea what the origin of the Platinum anomaly, so I cannot state if it is indeed extraterrestrial.

    2) I have no idea what the actual chronological offset in GISP2 is at this depth. The example I used for the above age is an optimistic estimate for the platinum anomaly. it could be more, it could be less.

    The only thing I would conclude is that it is most likely not at the absolute age given in the cited paper.

    What I will also say though is that I would like to see replication of this platinum anomaly in the GRIP ice core. If it does exist in the GRIP core it would make the perfect isochron to synchronise the two cores at this depth.

  • Casual visitor

    Aneney,

    Please take a look at the paper

    http://210.38.138.6:9020/editor/UploadFile/The%20mysterious%20onset%20of%20the%20Younger%20Dryas%20.pdf

    for resolving the dating issue. It sets the onset of the YD at 12,847 +/- 3 BP, which conforms with the GISP2, but not with GRIP. GRIP is superseded by NGRIP.

    By the way, Petaev marked the LSE in his paper on the graph 1, quite correctly.

  • Casual visitor

    agimarc,

    From your paper,

    “All four pyroclast types appear to have a fluid-like, poly-lobate clast shape. This suggests that these
    clasts were formed by ductile fragmentation. Tephra which is formed by brittle fragmentation has a
    more blocky shape with straight edges.” (page 92)

    This means that there was no volcanic ash produced in this explosion, but only liquid droplets. Is it a bit strange that at least 3 km of the overlying terrain were missing in action or turned into droplets ? It could only have happened if there was an impact to bore the hole to the lava chamber.

    Liquid droplets have no vesicles, so you cannot find trapped gases. They escaped. Is there any other piece of evidence that might convince you ?

  • Jonny McAneney

    Casual Visitor,

    I cannot argue whether an impact caused the eruption of Laacher See or not. I was pointing out that there was a weakness in your model when you link the Laacher See eruption to the platinum anomaly in the GISP2 ice core, since you specifically state “However, Petaev’s Greenland data point to a *minor* peak of Pt a decade earlier. This is the impact that coincides with the Laacher See tephra”.

    When you use a chronology to support your argument, then the question of “when” something happens becomes important and debatable. You use the platinum anomaly as support for an impact/eruption correlation. in other words, you are comparing the varve chronology to the ice core chronology, and more to the point you are comparing two different proxies (tephra in varve to platinum in ice), in two chronologies with inherent uncertainties.

    Regarding tephra of Laacher See in ice cores. The paper you link to does not state they found tephra from Laacher See in GISP2. What it staes is that they have two large Sulphuric acid horizons whose ages are compatible with the Laacher See eruption. This is different from finding tephra shards (i.e. shards of volcanic glass) that can be chemically analysed and compared to the chemical signature of the tephra fall out at the volcanic source. Researchers have fallen into this trap before with linking sulphate signals to volcanic eruptions before. For years the large sulphate signal dated to 1641 BC in GICC05 was thought to be from the eruption of Santorini (AKA Thera), but when tephra in that layer was analysed it was found to be from the Alaskan volcano Aniakchak.

    Regarding the varve chronology, when doing any layer count of stratified material one must consider the possibility that not only have you missed counting a layer, but also the possibility that you may have interpreted a single year as two (or more) years. This is why there is always a +/- around a cited date. I am not familiar with the paper that determines the varve age of the Laacher See eruption, so I cannot comment on exactly what they meant when they say +/- 40 years. Regardless though, there is still the issue of suck in and smear when trying to link an ice core date (which has its own uncertainties even without the issue of a chronological offset) to a varve chronology that also has an inherent uncertainty.

    Regarding references, here you go

    Torbenson et al (2015) https://www.researchgate.net/publication/281377222_Asynchrony_in_key_Holocene_chronologies_Evidence_from_Irish_bog_pines

    Lohne et al (2013) https://www.researchgate.net/publication/239527057_Precise_14_C_ages_of_the_Vedde_and_Saksunarvatn_ashes_and_the_Younger_Dryas_boundaries_from_western_Norway_and_their_comparison_with_the_Greenland_Ice_Core_GICC05_chronology?el=1_x_8&enrichId=rgreq-4867869a0f8819a205348af8a044f526-XXX&enrichSource=Y292ZXJQYWdlOzI4MTM3NzIyMjtBUzoyOTIwMTc1MjAzMDAwMzZAMTQ0NjYzMzgxMDU4Mg==

    A final note regarding ice core chronologies. As the above papers demonstrate, the ice core chronologies are inherently incorrect beyond their counting errors. Recall the 1641 BC eruption date in GRIP? It is dated as 1667 BC in GISP2. Between this layer and the Platinum anomaly layer at 1712 meters we have 108 metres of missing ice! If the ice core could possibly manage to be correctly dated at 1712m depth in absolute terms would be an astonishing fluke.

    In order to have a correct core at this depth we would need an isochron that is accurately and independently dated. The Laacher See tephra if found in the ice core (not just a large sulphate signal) would be a decent isochron to use given the reasonable dating using the varve chronology.

  • Casual visitor

    Page 10 of the Andronikov paper that is the point of this thread: ” The sample LUT-7
    not only displays somewhat unusual trace element
    characteristics, but also displays much stronger
    PGE signals on the ICP-MS spectrum compared
    with signals for other samples from this and other
    outcrops (Table 4).
    ” (also look at graphs)

    This means that the Pt signal is detected exactly in the same thin layer that contains the LSE tephra.

    Pt is abundant in space, but is exceptionally rare on Earth. This means impact.

  • Jonny McAneney

    Casual Visitor

    You are missing the point, which is stated eloquently in the the most recent paper you link to

    “The precise timing of the Younger Dryas onset is uncertain.
    Three Greenland ice cores provide different dates (Southon, 2002) which, in view of the proximity of the coring locations (Johnsen et al., 2001), seem to be due to layer-counting errors: 12,650 cal BP in GRIP (Johnsen et al.,1992),12,850 cal BP in NGRIP (Rasmussenet al., 2006; Steffensen et al., 2008),12,950 cal BP in GISP2 (Grooteset al.,1993; Meese et al., 1997; Alley, 2000).”

    GRIP and NGRIP form two of three ice cores that formed the GICC05 timescale. This timescale has been shown by Lohne et al (2013) and Torbenson et al (2015) to be at least 70 years too old at the end of the younger dryas and after. These two ice cores date the Younger Dryas onset the later than GISP2, so logically, GISP2 must also be too old. The question is by exactly how much are each of the ice cores too old. That we do not yet have an answer to. Fiedal is writing at a time before we began to realise that the absolute dating of ice core chronologies are questionable.

    To try to be completely clear on this matter. There exists in the ice core chronologies, whether it is GRIP, NGRIP, DYE3, GISP2, an inherent chronological offset, one that is only just being revealed, and that this offset is not within counting errors. So it doesnt matter what ice core dates one uses for the start of the YD, since the these dates will incorporate the inherent chronological offsets, and you end up with circular arguments. I would also be extremely suspicious of a date given to an ice core date at this depth given to a precision of +/- 3 years. Vinther et al (2006) give the termination of the Younger Dyras date in NGRIP (using GICC05) as 11703 (b2k i.e. before 2000) with a maximum counting error of 99 years. i.e. 11653 BP +/- 99 years. So it seems odd to me that a +/- 3 for the dating of the Younger Dryas beginning could be so much better than the dates given by the actual ice core workers doing the dating.

  • Jonny McAneney

    Casual Visitor,

    You are pointing out that platinum appears to be in the tephra debris around the Laacher See site. But no tephra from Laacher See has been found in any ice core, which means that one cannot positively link the site chronology to the ice core chronology.

    Besides, PGEs can be from volcanic sources, not just from extraterrestrial impacts, and so even if there tephra from Laacher see was found in the ice cores in the same layer as the platinum layer, one must at least consider the plausibility that it has a terrestrial origin.

  • Casual visitor

    The onset of YD came later and it came at various parts of the world at various times. It happened to be a single year event at the varve site, or 3 year event at the site in the Atlantic ocean, but probably not on the same year/years.

    The point here is that there was a volcanic eruption (LS), and two impacts somewhere on Earth (Pt spikes). These are to serve as excellent time markers.
    If these two are isochronous, then they are to be found at the same layer. The Andronikov paper that we debate here found the spike of Pt in the layer with the Laacher See tephra, which makes them contemporaneous to the degree of uncertainty in measurement. This might be here a decade or so, but certainly not 170 years, or several decades.

    If Pt and LS tephra are on the same spot and quite likely at the same time, the next step is to check whether one has something to do with the other, which is what I do here, by multiple approaches.

    If you wish to suggest some time span for the LUT-7 sample zone, I am willing to listen.

  • Casual visitor

    Petaev et al considered the possibility that Pt has a terrestrial source, and rejected that option. Pt as a metal is siderophilic and so all of the Pt has ended in the Earth’s core, bound to iron. Practically all of the Pt that is being mined on Earth on few locations has extraterrestrial origin. Namely, it comes from the bodies of ancient impactors.
    We are talking here about 2-3 orders of magnitude larger concentrations than in Earth’s crust.
    Besides, there are 340 volcanoes in the Eifel fields, and no high PT concentrations nor mines. It would be quite odd to expect that the LS magma is the source of Pt, when the element is not present in significant quantities in the magma from all the other eruptions from the area. It means that the source of Pt in the ice cores should be the same as in the LUT-7 layer hat contains the LS tephra.

  • Jonny McAneney

    Casual Visitor,

    I will ask this. Is there Laacher See tephra in the GISP2 ice core layer that contains (or even adjacent to) the Platinum anomalies? Because without this you cannot link GISP2 to Laacher See. the Andronikov paper only found the spike of Pt in the layer with the Laacher See tephra in terrestrial debris, not in the ice cores. Without Laacher See tephra in the ice core, you cannot positively prove that the platinum anomaly in GISP2 occurs contemporaneously with Laacher See. Hence you cannot show that the ice core platinum is contemporary with the platinum found in the sediment.

    Do not get me wrong, I am not arguing against the platinum being due to an impact, be it on a volcano or elsewhere. It may well be impact related for all I know, or it could be terrestrial. Just because Petaev et al dismiss the idea of it being terrestrial in origin does not mean that it is not. There have been numerous models in science that have been found to be erroneously dismissed. I remain completely open minded about its origin.

    What I am trying to do is to show the weakness in linking the two ice core chronologies in light of new and current research. Ice core chronologies are not the absolute standard of dating that they were once thought to be, and there is a danger in linking these chronologies to other non-ice core, geophysical markers without definitive proof (such as matching tephra horizons win stratigraphic contexts).

  • Hermann Burchard

    Jonny, – “Laacher See tephra in the GISP2 ice core”

    You can’t expect LS tephra in ice cores from Greenland for the simple reason of the butterfly pattern in the ejecta geography, pointing NE & SE, see Fig. 2.9 page 28 in Gert-Jan Peeters’ Univ. Ghent MS thesis.

    BTW, that pattern in-and-by-itself is prima facie evidence for a non Earth sourced impact event, as pointed out above.

  • Jonny McAneney

    Hermann,

    I agree with you that one cannot expect to find tephra in the ice cores from ANY volcanic eruption. However, the directionality of the immediate fall-out blanket of an eruption does not dictate whether volcanic shards of tephra reaches the Greenland ice caps.

    In order for tephra to arrive upon an ice cap the eruption must be large enough to inject volcanic tephra into the stratosphere, and for the stratospheric wind patterns to transport it over the ice cap, or sufficiently close to the ice cap to permit tropospheric transport of stratospheric fall out onto the ice cap.

    This is why we find Tephra in the GISP2 ice cores from the the eruption of Changbaishan in China/Korea in AD 946 and the Indonesian eruption of Samalas in AD 1257, despite the directionality of their immediate tephra fall out blanket. Admittedly, these eruptions were both ranked VEI 7, which would help to propel significant amounts of ash into the stratosphere.

    Laacher See was a VEI 6 eruption. So was the 17th century BC eruption of Thera and so was the AD 79 eruption of Vesuvius. No tephra from these two eruptions have yet been identified in ice cores. So I would not be surprised if tephra from the Laacher See eruption cannot be found in the Greenland Ice cores.

    However, it may well be that because of the chronological offsets in the ice cores, researchers are looking in the wrong layers for tephra. For years ice core workers were looking for Vesuvian tephra in a layer they dated as AD 80. They eventually found some and proclaimed they had found Vesuvian tephra. Then we found out that the date of that ice layer was actually AD 87/88, and so the tephra could not possibly be Vesuvian in origin. No one at the time had investigated the 72/3/4 “AD” layer (in the GICC05 timsescale) to look for tephra. Why would they if they believed that their ice core was correctly dated, as evidenced by the fact that they proclaimed this layer to be a zero error horizon?

    This is why I emphatically point out how risky it is to align two stratigraphic records unless you have the same identical proxy markers in each record.

    And regarding the fall out pattern, yes it is reminiscent of an impact c.f. the Tunguska tree-fall pattern. But that doesnt mean it is. The butterfly-shaped isopach is unusal but but not unique. Directionality close to the volcano could be caused through plume collapse and pyroclastic flows/density currents tracing the topography of the land (see the samalas pyroclastic flow map http://www.pnas.org/content/110/42/16742/F1.medium.gif). These flows can also produce phoenix clouds which can then disperse material over a much wider area than topography would normally permit. As for the wider fall out far from the volcano, volcanologists looking at the volcanic deposits have reconstructed that the eruption column penetrated the stratosphere, before dipping back to the troposphere where winds carried it north east. later in the eruption the wind direction changed depositing it to the south east instead. This explains why the isopach shows a greater area of thicker deposits to the north east than to the south east. An impact origin is not required to explain the isopach data.

  • Casual visitor

    The Petaev’s data shows that the Pt took 20 years to settle, which means that it was placed in Earth’s orbit. Only an impact can be so powerful to put dust into orbit. Volcanic dust settles faster. The source of Pt was also highly depleted in Al, which is odd for an Earth’s source and further confirms the impact scenario.

    You’ll have to find not only the terrestrial source of Pt, but also a mechanism to inject the dust into orbit to disprove Petaev’s claim.

    If LS is an impact site, based on detection of RREs and PGEs in tephra, on ejecta pattern distribution, etc, then it must be the same impact event simply because impacts of that magnitude are very rare.

    If your stated margin of error is 170 years, and the occurrence rate of these kinds of impacts greatly exceeds that error margin,
    by at least an order of magnitude for the 300 m impactor, then we are observing the same event.

    You might synchronize your watches.

    The weakness here is not whether the Pt in ice cores is impact based, but whether the LS is an impact site. This we might debate further.

    So, can you please comment on my remark to agimarc that the pyroclasts from the LSE contained no irregularly shaped volcanic ash, but only aerodynamic shapes ? Liquid droplets are what one might expect from an impact.

  • Jonny McAneney

    Casual Visitor,

    To clarify, I do not know what the chronological offset in GISP2 is. I am stating that there likely is an offset. The 160 year offset was an off-the-cuff estimation based upon information I had to hand. It could be more, it could-be-less. We have a varve dating of Laacher See. The ice core dates can be, and likely will be. This means that the Platinum in the ice cores is younger than the Laacher See eruption. It doesnt matter if you have platinum in Laacher See deposits and platinum in the ice cores. It is not enough to link the two together. It is very risky to assume that two similar signals are the same event,regardless of rarity.

    So let me ask this. If the impact at Laacher See was so powerful to put dust into orbit, and this dust then settled out over the Greenland ice caps, where is the pulverised Laacher See dust in the same layer as the platinum anomaly in GISP2?

    Regarding the shapes of pyroclasts. Many pyroclasts found in other volcanoes have aerodynamic shapes due to being ejected from the eruption in a partially melted state. https://books.google.co.uk/books?id=imwYphvLeRgC&pg=PA20&lpg=PA20&dq=pyroclasts+aerodynamic+shapes&source=bl&ots=48GGiJRVN-&sig=eoXO2yu5kAKT49yA1Rqk6zF_aOI&hl=en&sa=X&ved=0ahUKEwjUiMKx_cDPAhWCOsAKHfS1BbcQ6AEIPjAI#v=onepage&q=pyroclasts%20aerodynamic%20shapes&f=false

    Aerodynamic shapes are not unique to Laacher See.

  • Casual visitor

    Quotes from Peeters (paper suggested above by agimarc):

    1. “Using the obtained density variation for grain size, instead of the linear decrease suggested by
    Bonadonna and Philips (2003), the tephra dispersal modelling reveals that less tephra is being deposited
    in the more proximal areas and more tephra is being deposited in distal areas. This difference between
    modelled fallout using both density – grain size relationships, increases with increasing plume height,
    erupted mass and increasing maximum wind speed. Especially in highly explosive eruptions, there
    appears to be a significant increase in tephra being deposited further away from the vent, than what is
    predicted from the model using the density variation suggested by Bonadonna and Philips (2003). This
    suggests that models being used for hazard assessment for large eruptions should definitely incorporate
    a more detailed density – grain size relationship than what has been used so far. ”

    This implies that the LSE has an atypical distribution of tephra by grain size, so that the models had to be adjusted to incorporate it.
    This by size distribution fits the impact hypothesis.

    2. The ejected magma volume did not only dwarf the erupted volume of the more than 300 scoria cones scattered
    throughout the Eifel region, it was also larger than more recent Plinian eruptions like the AD79 Vesuvius
    eruption, the 1980 Mount St Helens eruption and even the 1991 eruption of Pinatubo. …
    The influence of external water during the beginning and ending phases of the LS eruption was very important.
    (p11)

    This means that the LSE is by far the largest event in the area that is filled with volcanoes. This is an oddity. It is not an oddity if it was an impact, but otherwise…

    3.The Western Eifel volcanic field (WEVF) extends over 600 km2 and is made of approximately 240 volcanoes
    which are aligned in a NW-SE direction. … Even though the EEFV is only made up of 100
    volcanoes, it contains four highly differentiated phonolitic volcanic complexes: Rieden, Wehr,
    Dümpelmaar and Laacher See… the fields originate from two different sources in the mantle.
    (p13)
    There are 340 volcanoes in the complex, but only four explosive ones, of which the LS is by far the greatest.

    4. Oppenheimer (2011) acknowledges that the volcanism of the Eifel is
    related to the collision between the African and Eurasian plates and adds to it that the fact that
    volcanism is concentrated in bursts could possibly be linked to the loading and unloading of the
    European continent by ice sheets. … The oldest well-documented phase is that of the Rieden volcanic complex
    (ca. 380 – 430 ka) during which 5 km3 DRE phonolitic magma erupted. The second phase is characterized
    by the construction of the southeastern subfield of the EEVF approximately 190 – 215 ka ago. …
    The first Wehr eruption was dated at 215 ± 4 ka
    (40Ar/39Ar dating; Van den Bogaard, 1989) and most scoria cones in the subfield are formed within
    20,000 years after this first eruption. The third phase (ca. 100 – 150 ka) consists of two minor phonolite
    eruptions: the second eruption of Wehr volcano, around 151 ± 11 ka, and the 116 ± 16 ka eruption of
    the Dümpelmaar (both 40Ar/39Ar dating; Van den Bogaard, 1989). Both eruptions formed a phonolitic
    volcano. The fourth and last phase is characterized by one large scale eruption, namely the 12,900 ± 560
    a (40Ar/39Ar dating; Van den Bogaard, 1995) eruption of the Laacher See volcano. …Even before the LSE, the present Laacher See (LS) area had a relative negative topography to its
    surroundings and supposedly already contained a shallow lake. (p15-16)
    Details of the mentioned 4 explosions point that they are very rare.

    5.A unique feature that attracted volcanologists to study the LSE and its deposits is that the magma
    chamber of the Laacher See Volcano was almost completely emptied during the eruption (Schmincke,
    2004). In most cases only a limited fraction of the melt in a magma chamber is erupted whereas the bulk
    leftover magma remains in the magma chamber or is withdrawn to deeper levels. Due to the seepage of
    water into the magma chamber during the ending phase, new batches of magma which would
    otherwise not have erupted were thrown out as a result of pulsating phreatomagmatic explosions.
    The almost complete emptying of the magma chamber made it possible to model the pre-eruptive magma
    chamber of LS before it erupted. The material stored at the top of the magma chamber, which erupted
    first, is now preserved as the lowermost deposits whereas the topmost deposits represent the bottom
    of the magma chamber. Wörner and Schmincke (1984a) stated that the magma chamber was zoned from highly evolved, volatile-rich and crystal-poor phonolite at the top towards slightly more mafic, crystal-rich phonolite at the bottom.
    (p16-17)

    Another oddity: complete empyting of the magma chamber. An oddity for a volcano, but not so for the impact scenario. This is exactly what would be expected from an impact. The uppermost part was volatile rich because the impactor would have contributed the volatiles, and crystal poor for the same reason, while the bottom part was denser and erupted after the water from the lake rushed in into the opened cavity to initiate the later phase of the eruption.

    6.Wörner and Schmincke (1984b) argue that a third differentiation stage was responsible for the
    discrepancies of oxides between the calculated and observed magma compositions at the top layer of
    the magma chamber. Because an unrealistically high volume of the lower part of the zoned magma
    chamber would need to crystallize in order to achieve the extreme trace element enrichment towards
    the top layer of the magma chamber, or magma mixing would require an extremely fractionated liquid
    as one end-member, liquid-state differentiation or liquid-state thermogravitation diffusion (LSTD) could
    have caused the extreme enrichment….(p19)

    The RRE enrichment in the upper part of the magma chamber (as expected from the alternative impact scenario) is extremely difficult and even found unrealistic to explain from the volcanologist’s point of view. Over and over again they had to invoke the word ‘extremely’, ‘extreme’ to cope with the observed facts.

    These uniquenesses by the power of the occam razor point to the alternative explanation that naturally explains them by standard theory of impacts.

    7. Wörner (1982) predicted that the magma chamber of LS was set in shallow crustal
    levels around 3 to 6 km depth.(p20)
    All that overlying rocks were supposed to have been blasted away by the explosion, but produced no shards of irregular shape. Only an impact can do such a thing. Remember the eruption of he Eyjafjallajökull (or whatever is it’s name), the Iceland volcano from few years ago. It made a lot of ash that was irregular in shape. No such ash in the LS tephra is an extreme oddity.

  • Casual visitor

    Aneney,

    It was not the LS eruption that put the dust into orbit, but the main impact a decade later that was much more powerful. Devastating enough to separate epochs, and equally rare. But the peaks of Pt indicate that there was a smaller impact a decade earlier, certainly from the encounter with the same object, as in the SL9 scenario. One orbit earlier.

    The LS event was a precursor event if it is an impact site, and as a minor impact it only put dust into the stratosphere, which is why it might not show in the ice cores. not in large quantity anyway.

  • Jonny McAneney

    If the Laacher See impact was minor, and only injected dust into the stratosphere, the fact that platinum from the impact reached Greenland should also imply that Laacher See dust would also reach Greenland, since one would have mixing of material at the impact site.

    The ice core platinum concentrations may well be extraterrestrial in nature, but the issue is whether they are coeval with Laacher See, and currently I see no concrete evidence to support that. I wish you luck though in the publishing of your data in peer review.

  • Casual visitor

    It is true that if Pt from the impact site ended in the ice cores, then the LS dust must have done that too, at least a small amount of it. But, how do you know that the small amount of dust which did end up in the ice cores, did not come from the LS ? Petaev checked the relative abundances, which means that even a tiny amount of dust was sufficient for his task.

    I feel that discussion has come to an end, presumably due to the exhaustion of participants. (Or perhaps because I raised too many questions at once. Sorry.)

    For the end, I will ask just one simple question: is the presented data sufficient to raise a reasonable suspicion that LS is an impact site ?

    If yes, they must be coeval, if not, the coeval minor impact site is elsewhere and the LSE is at some other time, in which case dating records need recalibration.

    I would not do recalibrating just because the LS tephra was not yet found in the ice cores. If somebody finds it at some other time layer, then it would be a good reason but until then I am not convinced either that the stated dates are erroneous by centuries. A missing parameter is not a proof of its non-existence, only a reason for perhaps further research.

  • Hermann Burchard

    Jonny speaks “Without Laacher See tephra in the ice core, you cannot positively prove that the platinum anomaly in GISP2 occurs contemporaneously with Laacher See.”

    & doublespeaks:

    “I agree with you that one cannot expect to find tephra in the ice cores from ANY volcanic eruption.”

    Also, you do not understand impact volcanism: “Many pyroclasts found in other volcanoes have aerodynamic shapes due to being ejected from the eruption in a partially melted state.”

    See my earlier post on flawed Ivanov-Melosh (2003) paper

  • Howdy all –

    Another paper with an extended discussion of volcanic activity in the Eifel volcanic field. CV summarized a bit of it in an earlier comment. Cheers –

    http://www.klimaundsedimente.geowissenschaften.uni-mainz.de/Dateien/Foerster_etal_Tephra-stack_Geoplacha-2016.pdf

  • Howdy CV –

    From the following, it appears that the LS tephras were rather run of the mill Plinian tephras with normal inclusions / vesicles. Cheers –

    http://link.springer.com/article/10.1007/BF00493689

  • Casual visitor

    Hello agimarc,

    You are looking for a proof that is either impossible, or extremely difficult to be obtained. The aerogel which was used on Stardust was specifically designed to collect samples in vacuum of space and was kept in special conditions on the spacecraft. I’ve seen that material. It looks like a sponge made of glass. Very ugly and dangerous stuff.

    Do you really believe that it would be possible after 13 ka to extract a bubble of gas from tephra that was exposed to weathering for all the time since and convince a skeptic like you into anything about it ?

    As for the papers on LS, I don’t think that any one of them has considered impact volcanism as an option and then evaluated the arguments.

    Check the point six from my list: they found enrichment in RREs unrealistic and impossible to explain. The RREs are common in space and are the tell-tale signs of impact, especially when coupled with excess of PGEs.

    Why are the solids not a good enough proof to you ?

  • Jonny McAneney

    Hermann,

    defintion of doublespeak: “Doublespeak is language that deliberately obscures, disguises, distorts, or reverses the meaning of words.”

    I have not done so. I have pointed out two scientific facts:

    1) The only true way to prove a link between a volcanic event in one chronology to a volcanic event in another chronology is through finding and identification of tephra from that volcano in both chronologies.

    2)Not all volcanic eruptions deposit tephra in Greenland Ice cores.

    This is not doublespeak, and I have not deliberately obscured, disguised or distorted these facts. Indeed, I did explain why it is that not all volcanoes deposit tephra onto the Greenland ice cap. If they did, tephrochronologists would have a far easier time with the bounty of data.

    I can see how you may have thought it was double speak, where on one hand I say that the only way to prove a connection is to find ice core tephra, and on the other seemingly saying it may not be found. That though is not obscuring the issue, it is simply stating the facts. Laacher See tephra may never be found in the ice cores.

    Regarding your assertion of (and I presume you mean me here) my lack of understanding of impact volcanism. I will freely admit that I am not an expert in either regular or impact volcanism. However, I am confused by this last statement in that you seem to be implying that aerodynamic pyroclasts are a signature of impact volcanism only. or at least that is my inference? Would this inference be correct, and if so, are you denying that aerodynamic pyroclasts, such as so called Pele’s tears, are not observed in regular volcanism observed in modern volcanoes that are not impact induced? So if these aerodynamic pyroclasts occur in regular and impact volcanism, how can one possibly use them to support an argument for one mechanism over the other?

  • Jonny McAneney

    Casual Visitor,

    Yes , I think we have indeed come to an end of our discussion on the matter, and to continue would risk just treading over the same ground as we go around over circles. I will answer your question though. I am not currently convinced that the evidence to date is conclusive that Laacher see is an impact site. To put this clear, I am not adverse to the idea of it being an impact site, merely that at the moment I am not convinced that it is. That doesnt mean I wont be convinced (or even lean more that direction) in the future with stronger evidence.

    I have enjoyed our tete-a-tete though, and appreciate your efforts to present your argument.

  • Hermann Burchard

    A note of no import: Laach is archaic (OHG) for lake, and is preserved only for Abbey Laach (Maria Laach) founded 1092, a tourist Mecca for the early pre-gothic architecture. (See here.)

    Laacher See being a pleonasm (“Laker Lake”), my preference would be to use “Laach,” but the Eifel folk must have their say.

  • Casual visitor

    Aneney,

    I’ll answer the question regarding the pyroclasts.
    There is overly too much of them in this case, which means that there was too much energy in the system. This is unusual for a volcano, but can be explained if an impactor provided the extra energy.

    That is not a definitive proof, but just one more of the many tell-tale signs of impact. Between the two competing explanations, the pure volcanic event case has often more difficulties in explaining the various markers, and in the case of the enrichment with RREs even entirely fails to do so.

  • Howdy CV –

    What I was thinking of was excavation of layered tephras (remember there were multiple blasts) rather closer in to the vent where they are thick and more importantly buried and protected from the elements by all later layers.

    If cometary (Centaur) in nature, you should see an increase in heavy water similar what was observed in Hale-Bopp or 67P or about 3x natural concentrations on earth. Difficult to do? Absolutely, especially given welded tuffs are soft and relatively porous.

    I think we are at an impasse. Wanted to thank you for forcefully arguing another possible event / mechanism – another tool for the kit. I’m not where you are yet, but look forward to additional info as it arises. I don’t think we are at the end of this particular journey. More like the beginning.

    No expertise on volcanism. Simply another hobbyist. Cheers –

  • Casual visitor

    One correction of myself: ‘RRE’ should be ‘REE’ – rare earth elements. They are present in the lower tephra layer, which means in the upper part of the lava chamber. Thus they did not came up from another impact site and their presence in detected extreme quantity is ‘unrealistic’. Thus, them alone are a strong signature of impact.
    Chemically, there are also PGEs (Pt group elements).

    Physically, there is a large excess of energy, showing as the force of explosion. This is also a very strong proof, with multiple markers.

    On macro scale, the pattern of tephra distribution is an additional proof, especially in the plume direction (NE).

    One more proof, not yet mentioned, is the striking symmetry of the crater and a somewhat elliptical shape.

    As far as I know nobody ever tried to use heavy water as an impact marker. However, He3 has been used for that purpose successfully on the Tunguska site, but that was a recent event. I think that if one wants solid proof, the solids are sturdier.

  • Paul_Repstock

    Just so that readers do not misunderstand; I never suggested that the impact crater penetrated to the molten outer core or even deep into the mantle. What I referred to was the Impact Energy or shock-wave. Given Chixulub’s estimated potential energy of approximatly 1.30 x 10 (8th) Megatons of TNT or 10 Billion tons, the earth absorbed this huge amount of energy. My theory was that the energy was released on the other side of the globe.