The Kardashian Index: A not so scientific measure

By Kate

How might you measure a scientist’s ‘scientific worth’?

Today I will cover three indices developed to rank just how effective scientists are! In alphabetical and best to last order.


The h-index

This index attempts to capture both the productivity and citation impact of a researcher by measuring the number of papers and number of citations these papers have. To calculate, ‘h’ is the number of papers h that have at least h citations (the other papers (total papers – ) have no more than h citations). See figure below.

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The h-index


The i10-index

This is an index created by Google Scholar for Google Scholar – only they use this measurement. It is simple: ‘i10’ equals the number of papers with at least 10 citations.

An example of these first two indices in use can be seen in a screen shot of the Google Scholar Alfred Wegener – who had a mighty nice theory about continental drift (which forms a substantial basis of today’s understanding of plate tectonics). Unfortunately Alfred never made it to see how he would rank on the last index.

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Alfred Wegeners i10- and h-indices


The k-index

Here ‘k’ stands for Kardashian.1 An index defined as “a measure of discrepancy between a scientist’s social media profile and publication record based on the direct comparison of numbers of citations and Twitter followers”. To find ‘k’, divide twitter followers by total citations. Kim Kardashian is the highest ranked in the system for being one of the most followed people on twitter (with very few scientific publications).

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The k-index: Twitter followers versus number of scientific citations for a sort-of-random sample of researcher-tweeters

The inventor of the k-index (Neil Hall) declares “those people whose K-index is greater than 5 can be considered ‘Science Kardashians’”. These so called Kardashians are highlighted on the graph below. Hall advises that these Kardashians should get off twitter and get back to paper writing!!


So who are some of the greatest Science Kardashians?

k-index4

The Science-Kardashians

This k-index portrays science communication as a negative. But some would think, is it not the ultimate goal of science to be able to communicate it with peers and the broader community? I mean how else will you get those citations up? Social media and science can (and should) overlap in a Venn diagram’s space. The exchange of ideas and communication of results should be the goal!

What’s your K-index?

k-index5


1 For the full k-index article ‘The Kardashian index: a measure of discrepant social media profile for scientists‘ visit: http://genomebiology.com/2014/15/7/424

 

AGU Part 2: Impressions.

By Tanja

At the time of writing I am sitting at LAX (in this student’s opinion THE shittiest airport I’ve seen so far) with approximately 7 more hours to wait for my connecting flight to Sydney. I am traveling back from the AGU conference, and I am content after I have stuffed myself full of 13$ pizza, sitting on a piece of floor that I call “mine” now. I have also promised Thomas a blog on impressions upon return and since I have what seems like forever time in front of me, I’ll serve them up fresh.

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Oakland Bay Bridge and a fat seagull in the foreground

The AGU conference is big. Really BIG. I will not waste a lot of synonymous words to describe how big, because none of them are sufficient enough to properly describe it. Those among you who have already been to AGU know what I’m talking about, those of you who have not…. I will put it like this: Imagine you went to a 5-day festival that spreads out over 35 stages, with headliners and your favourite bands distributed over all those stages throughout all days. Stages are sometimes more than half a kilometer away and as you are trying to catch that really good band you so wanted to hear live, there are regularly 25 000 people in your way trying to catch their favourite band.

It is something like that. Queuing for beer on the first day included.

Except it’s not a festival. It’s basically a large business meeting. It is a chance for you to present your work in form of a talk or a poster and chat to other people in your field or potentially outside your field. It is an excellent opportunity to meet people whose names you’ve only seen on papers you’ve read and to exchange some ideas and thoughts with them. For me personally it was a revelation that there are, in fact, more than 5.6 people in the world working on the inner core. It was good to see what they are working on. It was good to feel my brain kicking in action and asking these people questions, so for the first time in …. ever …. I felt like I knew what I was doing and could somehow judge what other people are doing. I can assure you this feeling will not last for long, so you can keeping breathing. As you were.

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Typical Alcatraz cell.
Not very much different from some dorms I’ve been staying at.

As jolly as it sounds there are some negative sides to such a large conference: it is exhausting. Especially if it’s your first time to San Francisco and you are determined to see EVERYTHING.

Sightseeing! Talks! Posters! All of the things!

It is nigh on impossible. I am not sure what I would feel like if I hadn’t been sightseeing at all, but I am under the impression that even so that conference is just too big and too long, no matter how good it is for your career.

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Alcatraz island

So in between running around to see all the touristy places I managed to attend some interesting talks and see some equally interesting posters. I got to talk to other students facing the same problems with their data like myself. I listened to a short talk about conducting seismic measurements at NASCAR races! I loved that one. There was an exhibition at Moscone centre as well – NASA had their stall, so I got to put Occulus Rift onto my eyes and got a good look at Mars from Curiosity’s perspective as I was spinning around.

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Shot from top of Coit tower. You can see the curvy Lombard street (second from the left) on this one

I have also seen some San Francisco :) Been to the wharves and said hello to sea lions on Pier 39. Admired Oakland Bay Bridge. Went up and down some steep streets. Went up Lombard Street and the little curvy bit on top – apparently it is the curviest street in the world. Went up Coit Tower to look at the city from up on high. Went to Golden Gate Bridge and walked on it! But most of all I’ve been to Alcatraz and took a tour around the island and the prison. It is definitely by far the most amazing thing I’ve done in this city. If you ever visit San Francisco (or you revisit it and you haven’t done this) – I highly recommend it. The island itself is beautiful, it offers some spectacular views of Golden Gate Bridge, Bay Bridge, city skyline and a scary insight into prison’s past. I had an audio tour narrated by ex officers and prisoners which makes it all the better.

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Behold! The Golden Gate bridge.

So yeah… overall impressions? I had a good time, albeit exhausting. In a week’s time I think I’ve done good in terms of both sightseeing and conference attendance. The tempo was crazy but it was worth it. The city is pretty and good to visit – has a soul to it definitely.

Flights back? Three words:

Delayed or cancelled.

Anything to declare?

Just a sore throat and a clogged nose.

Over and out.

Pushing an empty envelope

By Michael

Some of you may have heard this embarrassing story from back in October. The incoming Chief of the Commonwealth Scientific and Industrial Research Organisation (CSIRO), Dr. Larry Marshall, was being interviewed by ABC Rural about what to expect at CSIRO under his leadership from the start of 2015. The interview covered his vision of how CSIRO’s scientists will continue to deal with the challenges that face the agricultural industry in Australia.

On top of that list of challenges is water scarcity, and it has been ever since there has been an agricultural industry in Australia. It was during this part of the interview that Dr. Marshall brings up water-dowsing by saying, “I’ve seen people do this with close to 80 per cent accuracy and I’ve no idea how they do it.”

Before I go on to what I took from this interview and the reaction to it, I want to briefly describe what water-dowsing (or water-divining) is.

The basic concept works like this: a stick or metal rods (sometimes just a pendulum swinging over a map) in the hands of a dowser will be attracted to areas where groundwater is present. The dowser then uses the movements of their instrument to suggest where their client should drill for water. Dowsing has also been used to find mineral deposits and archaeological sites.

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Generic water-dowsing photo #1
Source

So how does water-dowsing supposedly work? The website of the Dowsers Society of New South Wales (unfortunately it’s a thing) isn’t that helpful in explaining how but they do mention things like “energy lines”, “energy fields” and “chakras”. So in a nutshell: magic.

The United States Geological Survey explains it much better here: “the natural explanation of ‘successful’ water dowsing is that in many areas underground water is so prevalent close to the land surface that it would be hard to drill a well and not find water.”

So Dr. Marshall should really be surprised that water-dowsers are unsuccessful 20% of the time.

The Dowsers Society of New South Wales give the second part of the explanation on their website: “pendulums are subject to suggestion.” The movements of the stick/rods/pendulum in the dowser’s hands have been found to be caused by phenomenon known as the ideomotor response. This effect causes the dowser to subconsciously move their body without consciously deciding to. Much like when people scare themselves with Ouija boards.

Now that I have covered the main points on what water-dowsing is, I’ll explain why I think the Dr. Marshall interview on ABC Rural is such bad press coverage for groundwater science in Australia and for CSIRO.

Firstly, water-dowsing is junk science that should have died off long ago. Unfortunately, other junk sciences like homeopathy, astrology and fortune telling have lived longer lives than they should have as well. One of the main reasons for their continued existence is people in highly regarded positions, like the Chief of CSIRO, sometimes giving great public endorsements.

Look at the Dr. Oz fiasco in the USA for a very recent example of an apparently credible person misleading the public. Unfortunately, it hasn’t taken too long for Dr. Marshall’s statements to be used as a shining endorsement for water-dowsing in a recent column published in Fairfax newspapers (see here). This article will no doubt give the false impression to the public that water-dowsing is still something worth investigating.

If I haven’t been clear already – it is not.

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Generic water-dowsing photo #2
Source

My second issue comes from Dr. Marshall’s and CSIRO’s response to criticism after the interview (see here, here and here). The critics aren’t being petty either. Water-dowsers can cost farmers thousands of dollars on badly placed wells, so it isn’t just harmless fun. However, Dr. Marshall’s only response so far has been to miss the point of the criticism and say that it’s CSIRO’s job to “push the envelope”. Apparently without any regard to how many people let him know that the envelope is empty.

The response from CSIRO’s twitter account during National Water Week was just as unimpressive: “Larry’s interested in helping farmers access water but wasn’t saying divining is the answer.” Again, they have missed the point of the criticism. We know he doesn’t think water-dowsing is the answer but he definitely gave it endorsement by giving the false impression that it actually works.

Lastly, the former Chief of CSIRO Land and Water, Dr. John Williams, pointed out another problem with the interview in a statement to Science Insider. He pointed out that Dr. Marshall’s focus on water scarcity was in the wrong direction. Dr. Marshall gave the impression that there is a problem with finding water in Australia. The problem isn’t finding water (scientists are aware of most of the productive aquifers), the problem is how we manage what we’ve got, and as Dr. Williams noted, “there isn’t much of it, and we don’t know how it’s replenished.”

What we do need is to develop new and improved methods of accurately estimating aquifer recharge rates, more robust modeling techniques for predicting catchment responses to water use and climate change, and better methods for managing and identifying water quality problems. Water-dowsing will never play a part in solving any of those problems.

The reason I put off writing this blog post until now was because I was interested in how Dr. Marshall might respond after such an obvious mistake. I was hoping he might finally listen to, and understand, some of the criticism that came after the interview. Unfortunately, we have now begun 2015 and he still hasn’t given a well thought out response. I guess we can only hope that farmers keep themselves up-to-date with all the great science that CSIRO Land and Water researchers are working on. I’m not doubting his sincerity about wanting to help farmers in areas where water is scarce. But if he really wants to make a constructive contribution to the discussion on water security in Australia he needs to set the record straight and understand that water-dowsing has no place even being mentioned.

The next big leap

By Thomas

I´m sure most of you have already seen this movie in the last few weeks, but as we have Christmas, I thought I refer to it for those of you who haven´t seen it yet1:

Why do I think this is a fitting short movie for Christmas?

Well, some 2000 years ago, three guys followed a star to find the birthplace of the saviour of human kind – if you believe this kind of stories.

In the future, if human kind wants to be saved (from extinction) we will have to follow planets – not stars. And that´s what the video is about. Maybe, in another 2000 years, on a far off planet or moon in the outskirts of our solar system (or even another one), people will celebrate the day their ancestors left their home world “to sail forbidden seas”.

Going to other worlds – we´ve done it before:

The adventure to Earth´s silent companion might have eased our “everlasting itch” for now – I hope for not too long though.

But before we prepare for human kinds next big leap:

Frohe Weihnachten to all of you!


1 Thanks to Pierrot for bringing the “Wanderers” movie to my attention.

AGU Part 1: The preparation frenzy

By Tanja

It is that time of the year. Everyone goes crazy, we are all busy but no one wants to work. We crank up the air conditioner and we are determined to ….. not wrap up the gifts. It is not Christmas I’m talking about – it is AGU. So we all crank up the AC and set down to make one last plot, try one more thing, do this and insert that. Print print print! AGU stands for American Geophysical Union and a big portion of RSES students and staff are attending to present their research. It is an annual conference taking place in San Francisco every December.

Students usually present their research in form of a poster on which they put their most important and significant figures with a bit of text briefly explaining what it is all about. They are assigned a certain time and space where they hang up their poster and have to stand next to it for a couple of hours and chat to anyone who expresses interest. This can obviously result in some good feedback on your research. Or not … I wouldn’t know. I have never been to a conference before. So when I submitted my abstract for AGU in August, I expected for it to be like that – the organizers will give me a “poster slot”, I will make one, chat to people, hopefully learn something new and that’s it. Just over a month ago I received an email from the AGU organizers saying that I should prepare an oral presentation, meaning – give a talk in front of bunch of people.

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My initial reaction to the invitation email.
Source

As someone who has never attended a conference, I have to admit that my initial reaction involved a few profanities having realized that I have been offered a talk at a conference that regularly hosts twenty thousand people. Of course, not all of them will be at my talk. But think about it – if even 0.5% of those people show up at the talk – it is still a hundred people I haven’t seen in my life. To say that I’m a bit scared and overwhelmed is an understatement. I am also equally flattered.

This kind of upped the ante on what I have to show. As you know from one of my previous posts – I am often stuck staring at my codes, trying to fix them. Now that I have to actually talk about what I’m doing I don’t have the luxury to discuss everything else that I have done and all the technical issues that I’m facing with an interested passer-by looking at my poster. I have to really show SOMETHING. So for the past month I have been frantically trying to work around technical issues and trying to improve my measurement methods in order to bedazzle the tiny crowd that will come to listen to me.

Wembley Legends Join Where’s Wally? For 25th Anniversary

My impression of a poster hall at AGU
Source

As if that’s not enough stress, Qantas has landed three planes bound for US in the past 24 hours. Due to… why? Smoke in the cabin? Nothing to worry about. The good news is – they landed them!

You know what hasn’t landed though? My allowance for staying the whole week in San Francisco. The money that I need for food and transport and whatnot during my stay still hasn’t showed up in my account (at the time of writing, 4 days before departure) due to some misunderstanding between administration and finance.

As far as my work goes, I was hoping for miracles but miracles didn’t happen. What happened instead is that I sort of realized what is causing my inversions not to work properly – and it is not a technical issue. So that’s a result in itself and has also pointed me in a new direction. Hopefully the AGU crowd will recognize that as well.

You want more good news? My talk is on the first day of the conference. I will see me some San Francisco afterwards. So stay tuned for the impressions of a first-timer to both US and conferences…

What can possibly go wrong?

Pyrites of the Caribbean 2

Subtitle suggestion: The one with the kraken (Editor’s Note: Wrong franchise!)


By Ingo

Pyrites of the Caribbean are fighting for the ANU 2014 Mixed Summer 9s Soccer Competition trophy. We are one football match away from the grand finals on Monday, 15th of December at Willows Oval. Though three key players are injured, Hannah – the optimistic team captain, is looking forward to this culmination of football competition!

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Top row from left to right: Rose Manceau, Tarun Whan, Liane Loiselle, Hannah James, Ingo Stotz, Piers Koefoed, Mathieu Duval and Thomas Haber.
Bottom row from left to right: Patrick Carr, Tim Jones, Lizzie Ingham, Patrick Goodarzi, Oleg Koudashev and Jessica Amies.

Season Summary

Everything started on Monday the 20th of October with an impressive win against the “Bayern Neverlosen” for 4-3. With the third game the Pyrites of the Caribbean positioned themselves on top of the table and have remained there throughout the whole competition, winning most of the matches, except for two draws – unluckily.

However, not everything has been joy and fun. Pat – rock defender, midfielder and striker – was injured and the medical team gave him one game off. With intense physiotherapy he was back on – defending, assisting and shooting once again.

Star striker Lizzie was injured running through a forest leading up to the 6th encounter, missing out on three games. To overcome the absence of two of their best players, the team was supported by Paolo, Holly, James and Maureen for several games in the season.

New acquisitions during the season were Kate and Liane, brought in straight from the laboratory. Liane scored a goal during her second game – 35 meters away from goal, eyes closed, hitting the ball with her knee leaving the goal keeper astonished.

Best player of the Universe

If we are to talk about the biggest impact in terms of best player – measured from start to finish – look no further than blue sensation Pat Carr. For the most part injury-free, the 24-year-old excelled under ultra-fan James Tolleys watchful gaze, serving up four goals, seven assists and countless saves during the competition, before capping off one of his finest campaigns to date last Monday – perhaps even his best.

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Patrick Carr

Quotes of the season

Man on!” and “Clear it!” by Oleg, Pyrites of the Caribbean’s goal keeper.

End of season

The end of season is soon and although the team is in a bit of trouble with two players injured, Piers and Ingo, the medical team is working to get them fit and ready for the grand finale. And two more are leaving for holidays, Tim and Thomas. Luckily, there are enough players to make two teams!

The Pyrites of the Caribbean have been undefeated throughout the whole competition and they’re determined to keep it that way.

Last regular game of the season will be played on Monday at 6 pm, followed by the grand finals at 8:30 pm. Everybody is welcome to watch and, being the last day of competition, we could use your support!

In related news – another interesting event to look forward to is the annual football match between the students and staff of the Research School of Earth Sciences. After the summer competition, the students are more than ready to compete against their supervisors and RSES staff members! The encounter will be held next year, in March. Be ready to take the challenge!

The Tunguska Enigma

By Thomas

It was an early June morning in 1908, somewhere in Siberia, as without a warning “the sky split in two and fire appeared high and wide over the forest”. That is at least how eyewitness S. Semenov recalls the event. (Wiki)

He goes on: “The split in the sky grew larger, and the entire northern side was covered with fire. At that moment I became so hot that I couldn’t bear it, as if my shirt was on fire; from the northern side, where the fire was, came strong heat. I wanted to tear off my shirt and throw it down, but then the sky shut closed, and a strong thump sounded, and I was thrown a few metres. I lost my senses for a moment, but then my wife ran out and led me to the house. After that such noise came, as if rocks were falling or cannons were firing, the earth shook, and when I was on the ground, I pressed my head down, fearing rocks would smash it. When the sky opened up, hot wind raced between the houses, like from cannons, which left traces in the ground like pathways, and it damaged some crops. Later we saw that many windows were shattered, and in the barn a part of the iron lock snapped.”

The Tunguska Event – a massive explosion that knocked down some 80 million trees over an area of 2,150 square kilometres (Figure 1) and luckily didn`t cause any (reported) fatalities. But what caused it? The most probable cause is an asteroid (or maybe a comet) entering Earth`s atmosphere and then exploding while still in the air, like the Chelyabinsk air burst earlier this year, just bigger. Other explanations that make for better Hollywood B-movie scripts are a comet that turned into a “natural H-bomb” when entering Earth`s atmosphere, a black hole passing through the Earth, Antimatter and last, but most definitely not least, a “Death Ray” build by Nikola Tesla.

Trees after the 1908 Tunguska event. Source

Figure 1: Trees after the 1908 Tunguska event.
Source

While these explanations are – how should I put this – “less likely”, they reflect that the Tunguska event remains a bit enigmatic to us. The air burst explanation is a good one, but it is nearly impossible to finally proof it. The event happened in a remote location, it happened at a point in human history when the dominant species on the planet was not homo cellphonecameras and fragments of the potential meteor where never found – and it is very, very unlikely that this will happen in the future.

A new study (Vannucchi et al. 2015) throws yet another explanation into the ring – an explanation which, if it would be true, would have a profound impact on the study of terrestrial impact craters, especially the way we identify them. Unlike on many of the other solid bodies in the solar system, impact craters on Earth are often not very well-preserved due to the constant erosion by wind and weather. To test whether an old structure that might be an impact crater is indeed one, scientists often have to rely on “fingerprints” of the impact event left behind in the target rock. Some of the most reliable of these fingerprints are the so-called PDFs, which stands for Planar Deformation Features. These features are left by very high shock pressures in mineral grains and can be studied under the microscope. What makes them such good indicators for impact events is that there is no other mechanism on Earth that can create the shock pressures as high as needed to create PDFs.

Of course, the Earth can build up quite some pressure from within and release this pressure in single events such as volcanic eruptions (Figure 2), but the shock waves generated by those events are not as powerful as those created by impact events. The reason for this is that the pressure that builds up under the Earth’s surface builds up slowly and will be released before it reaches the strength needed to create PDFs. In the case of an impact however, the pressure that is generated depends to a great deal on the speed of the impactor1 – and this speed can be very high.

Eruption of the Sarychev Volcano as seen from SpaceSource

Figure 2: Eruption of the Sarychev Volcano as seen from Space
Source

To illustrate the difference, let us suppose you want to destroy an oven, using only a metal pot filled with water and some tape. You can tape the lid tight on top of the pot and then put your pot on your oven and heat it up. You hope that the produced water vapour inside the pot creates enough pressure so that your whole pot explodes and destroys the oven.2 I don`t really know how much pressure you could create by this method, but if you get it high enough, what will happen is that your tape will fail and the worst thing that will (probably) happen is that the lid flies off and you stand in a cloud of very hot water vapour, which should be quite hurtful – but your oven should remain intact. Like the rocks in the Earth’s crust, the tape on your pot couldn`t hold the pressure over a certain point. If you however take your taped water pot and quite skilfully throw it out of a helicopter cruising 1 mile high and let it “land” on top of your oven … well you can see what happens to “metal things dropped from 1 mile high” in this video. And if there happens to be another “metal thing” on the landing spot, that one wouldn`t look much better either.

There are some speculations that the Earth itself, under special conditions, can indeed create explosive events strong enough to produce shock waves in a pressure range at which PDFs are formed. And here we come back to the study mentioned above and the Tunguska event:

About 3 km away from the epicentre of the Tunguska event is Mount Stojkovic, and there is a circular structure in which the scientist conducting the study identified samples with PDFs3 . Their favoured interpretation for the nature of this about 250 million year old circular structure is that it was created by a so-called verneshot – a “hyperexplosive volcanic gas eruption” which would be able to create shock features, such as PDFs. The 1908 event then might have been a smaller verneshot event.

The problem is that a verneshot is so far a not-observed, hypothetical event. Sure, the structure at Mount Stojkovic lies in the right geological setting that was envisioned when the verneshot idea was first proposed (Morgan et al. 2004). But apart from this there seems to be little to support the idea. The main argument in the study for the verneshot is actually not something supporting the verneshot idea, but the consideration of how unlikely the rival hypothesis is that instantly springs to mind: The structure at Mount Stojkovic might “just” be a 250 million year old impact crater that happens to lie close to the 1908 event. The argument made in the study is that an impact event and a later air burst event happening in the same location is so improbable that there must be another explanation – and therefore it must be a verneshot. And that part of the study is implausible to me.4

First of all, how can an event happening about 100 years ago make a 250 million year old event improbable? If tomorrow there is an air burst over Meteor crater in Arizona (Figure 3), which most definitely is an impact crater, will that suddenly make it not an impact crater? No!

Meteor Crater, ArizonaSource

Figure 3: Meteor Crater, Arizona
Source

Of course that is an unlikely event. In the study it is actually calculated how unlikely it is that a single air burst is happening over one of the craters that were formed on Earth within the last 250 million years: It is about 1 in 17000.5

That indeed seems like a low chance. But meteor air bursts are quite frequent. Yes, Tunguska was the biggest observed so far, so let us assume, an event like this only happens every 15000 years. That would still mean that within the last 250 million years about one of those Tunguska-like events is likely to have happened over an impact crater. And even if the probability would be much lower – it wouldn`t matter. We could probably find something unusual that has happened within 3 km of every meteor crater of this world. They will stay meteor craters regardless.

So we are left with two possibilities: We have impact cratering and air bursts, well documented and understood processes which happened to happen locally (!) close to each other, or the verneshot, a hypothetical event that, if really a thing, would mean there is more destructive power under our feet than we already know from “normal” volcanic and supervolcanic eruptions.

The second one might be more exciting, but the first one seems (so far) more plausible to me. But I`m fascinated by impacts, so I`m biased.

What do you think?


1 Other contributing factors are the size and nature of the impacting body and the nature of the target material.

2 Please don`t try that at home.

3 Actually, the study is a bit confusing for me: They sometimes use the term PDF and sometimes refer to the features as lamella, which as far as I understand it, is not necessarily a high shock pressure feature (If you want to know more about those features, see for example here: Reimold et al.). However, I`m not qualified at all to identify or judge this kind of features! So my confusion stems probably from a lack of understanding of the terminology.

4 Keep in mind: That does not necessarily mean that it really is implausible. I might just have misunderstood the argument.

5 1 in 17000 is the part of the Earths surface covered with impact craters that formed between now and 250 million years ago, thus an event happening at a random location (such as an air burst) has a chance of 1 in 17000 to happen “over” one of these impact sites. I also don`t quite get why, if you make a probability argument like this, you cut it off at 250 million years. I know it is the supposed age of the structure at Mount Stojkovic, but that shouldn`t matter if you want to know how likely it is that an air burst happens over an impact site. If an air bursts happens over a 300 million year old impact site, could we just shrug it off and say “Those things happen” but when the structure is 200 million years old the air burst suddenly becomes something special? For what reason?