This week’s podclast is the Geobloggers in the Pub episode. We talk about the KT boundary, including new research relating to it. Plus we lay into creationism in a pub-style chat fest.

Participants (links in brackets are Twitter feeds)

Chris - goodSchist (@yorrike)

Julia – The Ethical Palaeontologist (@morphosaurus)

Michael – Through the Sandglass

Dhiresh – A friend of mine and a geologist/geophysicist

The K-T Boundary and What Caused It

The paper we were discussing is by G. Keller et al. in Journal of the Geological Society, Vol. 166, 2009 [of London]. I can’t find the full name of the paper but I’ll keep looking.

Kim at All My Faults are Stress Related has a post on K-T extinction debates: cranky “skeptics” or reasonable science?

And the press release is available in various mass-media-filtered forms at Time, and the BBC.

Ethan Siegel’s Starts with a Bang has an article called What Wiped Out the Dinosaurs?, which is a superb run-through of the Chicxulub/KT impact. And you may want to read up on the Deccan Traps and how they relate to the KT extinction too. Also of interest, not because it explains the extinction, but because it’s another narrowly thought-out idea (or at least that’s how it’s been presented) is Insect Attack May Have Finished Off Dinosaurs which talks about the research from the book What Bugged the Dinosaurs?.

Creationism

You can look up Answers in Genesis yourself, as I won’t be linking to them, however the Talk.Origins Archive is a great place to look for basic questions and answers regarding the Evolution/Creationism debate.

Extra Note

The fossil of the seal ancestor is called the Pinniped, and information on the find can be found at the BBC and Eureka Alert.

Next Episode – Geoblogger in the Pub

We like to have a new episode of the podClast every fortnight. The next episode will be recorded at 1900 GMT on the 16th of May.

Contributing

If you’re keen to hear a specific topic talked about, or would like to join the discussion during the next episode, either leave a comment below or email chris [the at symbol] goodschist.com. You’ll probably also do well reading the details on joining the podclast. If you don’t have the time to join us but would like to contribute a 3-5 minute audio clip to the show simply record it, make sure it’s an mp3, and send it to the address above.

Credit

The intro and exit music was Roots Fi Cool by Burning Babylon.

Text Addresses

The post that accompanies this podcast can be found at http://www.goodschist.com/2009/05/07/the-podclast-episode-12/ or http://is.gd/xB3V and an archive of all podClasts can be found at http://www.goodschist.com/category/podclast/

What are ten things that every geology major ought to know about? The only restriction is you’re not allowed to list anything that has already been listed by a previous geoblogger. You don’t have to list everything, just ten important things

Mel at Ripples in the Sand has added to the list (both can be seen at the bottom of this post) and now it’s my turn. Embarrassingly I know nothing of “Pedogenesis” or “How aquifers work” as listed by Mel, but this is all about brushing up, isn’t it? : )

Here’s my list of 10 things every geology major should know:

1. The difference between absolute and relative radiometric dating.
2. Uranium-lead dating and how each element on the uranium 238 decay chain interacts differently with the environment.
3. The difference between a continent and a tectonic plate.
4. The properties of felsic, intermediate and mafic lava types.
5. How and why the melting temperature of a rock changes depending on the the concentration of volatiles therein.
6. What an ophiolite is and the significance of very old ophiolites.
7. The structure of the deep Earth (the upper and lower mantle including the MoHo and other zones)
8. The biological explanation for the formation of banded iron formations.
9. The insignificant difference between a volcanic sill and a volcanic dike.
10. How to spot changing environments in a stratigraphic column.

I could go on, but those seem pretty important. Below are Callan and Mel’s lists

Callan’s list:

1. The relationship between cooling rate and crystal size in igneous rocks.
2. The fact that rocks can flow, given sufficient temperature and pressure [and low strain rate, for the purists out there].
3. The idea that sedimentary rocks reflect specific depositional settings. By studying modern depositional settings and the sediments they contain, we can interpret ancient sedimentary rocks in light of the conditions under which they accumulated.
4. The fact that the chemical stability of molecular configurations (minerals) changes with different temperatures and pressures (metamorphism).
5. Large Igneous Provinces, and their potential role in tectonics and expressing mantle plumes.
6. Elastic rebound theory for the origin of earthquakes.
7. The notion of partial melting, and its relationship to Bowen’s Reaction Series.
8. An understanding of the carbon cycle, and an understanding of the atmospheric physics that facilitate global warming.
9. The role that rivers play in shaping the landscape: nickpoints, terraces, quarrying, abrasion, drilling of potholes, etc.
10. The Earth is 4.6 billion years old, which is extremely old in comparison to human life — and the reasons we think it’s so old [Pb isotopes, etc.].

Mel’s list:

1. Evolution.
2. Evidence for plate tectonics.
3. That fossils (and trace fossils) can provide more information about the rocks they reside in – depositional environment, chronology and correlation, water temperature, stratigraphic up, relative rate of deposition, water depth, etc.
4. And vice versa, the rocks can tell you a lot about the fossils that are contained within them – geography, taphonomy, chronology and correlation, etc.
5. The relationship between sediment production –> sediment transport –> sediment deposition.
6. How to identify minerals.
7. Differentiation and fractionation and how they apply to the planet, the solar system, and isotopes.
8. How aquifers work (or don’t work if we drain them too quickly).
9. Where our energy supply comes from. All facets from petroleum products, to solar radiation, to conductive metals extraction, etc. (These are also useful for seeking gainful employment as a geologist.)
10. Pedogenesis. How it takes thousands of years of chemical reactions and transport to generate the soils we use for agriculture. (And how we should be taking better care of them.)

I’m obsessed with science. However, once I’m done with my MSc, I’m off into the workforce for a time (potentially a long time). I haven’t ruled out diving into a PhD at some point, and in the mean time I want to continue to stay abreast with current research and I want to talk about research on this blog. Though subscriptions to the usual suspects (Nature and Science) aren’t out of my grasp, accessing articles from large journal databases such as Elsevier‘s Science Direct will cost me US$30 per journal article. And frankly, that’s just ridiculous. I know how much work goes into research papers – but $30 each? So far as I’ve been able to tell, research isn’t funded from journal sales.

So, my question to the geo-blogosphere, and the science blogosphere in general is, what’s the best way of getting full-text journal papers from a range of publications for reasonable money when you’re not within easy reach of a university or well-equipped public library? Preferably without resorting to illegality.

Update: In a case of blissful geoblog serendipity, Andrew Alden of About: Geology has just published a blog entry on open online journals within minutes of me publishing this article. Do great minds ponder alike?

But to be clear, what defines an epoch, an age, a period and era or an eon in the geological sense is reasonably arbitrary. There is nothing in particular one must consider as a marker between two periods. Time periods can be determined as the time when a particular large group of biota become extinct (like the P-T extinction event) or when there’s enough cooling for rocks to form and then for some of those rocks to still exist (like the Hadean-Archean boundary). A geological time is defined by geologists saying “that’s a good point right there because of this”, and nothing more. Brain at Clastic Detritus has an article expressing how annoyingly wrong a news article got this particular point.

In his latest article, The Anthropocene revisited, Andrew Alden takes another look at the concept of recognising the remarkable changes the human species has had on the geological record as a new geological epoch (Universe Today also has a good article up on this topic). The concept of the Anthropocene, as originally suggested by Nobel Prize-winning chemist Paul Crutzen in 2002 is discussed in a (freely available) GSA Journal paper entitled “Are we now living in the Anthropocene“, which I quote below;

A case can be made for its consideration as a formal epoch in that, since the start of the Industrial Revolution, Earth has endured changes sufficient to leave a global stratigraphic signature distinct from that of the Holocene or of previous Pleistocene interglacial phases, encompassing novel biotic, sedimentary, and geochemical change.
Zalasiewicz et. al., 2008

The current “sixth mass extinction” event we are causing started in the Holocene, the epoch that is defined as the 10,000 carbon years preceding 1950 (Zalasiewicz et. al. 2008, Wikipedia). This was the end of the Younger Dryas, the name given to the last ice age, and saw the beginning of the widespread extinction of mega fauna such as the Mammoth and the last Saber Tooth Tiger species. This, much like the extinction event at the Cretaceous-Tertiary boundary, began and continued slowly (in human terms) until a single event established it as a true geological boundary (and I’ve discussed this particular point before). It was a slow process. It began slowly (say, over a period like 10,000 years), and then ended suddenly (over a few months, but a few decades is basically the same in geological terms).

Though establishing a new epoch is probably best in terms of scientific enquiry, it would make the dawn of human domination of the Earth (the Holocene) a separate epoch from the widespread changes that domination brought with it. And if you consider the human phenomenon as a single natural process, it may make more sense to consider the beginning, duration and end as a single time period. And not to put too finer point on it, I think the amount of change currently occurring is so dramatic that establishing a new epoch maybe underplaying it. Should we begin to consider the establishment of a new Period once we can no longer sustain ourselves to cause as much change as we are currently? That being said, I’m in favour of considering everything since a yet-to-be decided point (and by point, I mean a very precise, slightly un-geological point, like new years eve 1850), as a new epoch, even if it does make the Holocene the shortest geological epoch ever. To be fair, I’m more interested in pre-Hadean events than the latter parts of the Quaternary.

References

• Zalasiewicz J, Williams M, Smith A, Barry TL, Coe AL, et al. (2008) Are we now living in the Anthropocene. GSA Today: Vol. 18, No. 2 pp. 4–8

Dwelling on the intricate series of events that lead to me dedicating a fifth of my life to a single field of science would likely bore the most patient of you. Rather than sending you to sleep, I’ll recall a short version of how I got into studying earth science and then quickly move into the interesting bits; why it’s worthwhile, why geology is such a great science and what I’m doing insofar as my MSc research is concerned.

Who am I?
My name is Chris. I’m in the final year of my MSc in Earth Science at Victoria University in Wellington New Zealand. I’m studying the geochemistry of chondritic meteorites and enjoy doing research that combines two of my major interests; geology and astronomy.

How did I get here?
In short, on a whim. It’s true for an outrageous majority of the people I took my undergraduate degree with and even most of the lecturers, that geology wasn’t their first flavour choice for the brain freeze inducing ice cream we call academia. The same rang true for me. I’d tried my patience with doing a BSc in computer science right out of high school. I quickly quit out of abject boredom only to start a career as an IT guy. Fixing computers, maintaining servers, writing and designing web pages. A go-nowhere-interesting, do nothing out-of-the-ordinary career choice I’d fallen into like a turbidity flow onto the abyssal plain. I eventually realised I needed to get back to university and do something I was genuinely interested in. So as my early twenties were drawing to a close, I headed back to school.

Taking a suggestion from a geologist friend and colleague, I signed up to all of the first level geology courses that were offered at Victoria, which happens to be my local university. By the end of the year I’d subjectively decreed that computers, dealing with millionths of a second, were intellectually pale in comparison to every major natural science expressed through the theme of millions of years. I changed my major from computer science to geology and here I am almost 5 years later.

What so good about geology?
So far as undergraduate study is concerned, geology is an incredibly social science. Its participants live together for weeks at a time on various field trips, which in turn encourages social mirth and mayhem to ensue both in and out of the field. The oft expressed stereotype of the bearded geologist, sidestepping lava flows en route to the next boutique pub isn’t as far from the truth as many would prefer.

Putting the social side of undergraduate study aside, I can’t express in simple terms just how fantastically broad a subject geology is. And just how complicated it can get. To quote Peter Barrett, one of my lecturers through my undergraduate degree;

Geology is like reading a history book. In a foreign language. With 90% of the pages ripped out.

I’m not sure if he made that up or got it from another truly inspired person, but it’s the perfect way to describe the science as a whole. Geology is where the natural sciences meet time. Physics, chemistry and biology, wrapped up in a enormous temporal package spanning billions of years. Though much has been written about the awe inspiring sites to behold should one gaze into the cosmos, there’s an equal array of wonder below your feet; something most people, unfortunately, can’t fully appreciate.

I’m an igneous geochemist if you go by my research, and I don’t have much time for things such as sedimentology. However, even in the most boring of sedimentary rocks, there’s often a riveting story to be told. Take Wellington, New Zealand, for example. The rock around here is dead boring from a petrographic standpoint. Quartz grey wacke and loess blown into place during the last glaciation. But how did that grey wacke form? Well, millions of years ago as Gondwana was in its death throws and Australia was tectonically rifting from east Antartica, large turbidity flows of sediments, hundred of millions of tons in mass, crashed through the ocean depths, depositing themselves on the ocean floor, specifically the submerged continental mass that would eventually make up part of New Zealand. The image I paint in my mind’s eye of these events is just breath taking. The shear scale of the deposition would be truly magnificent to behold. And this is an area of geology I don’t care much for.

My Research and Specific Geological Interests
On the other hand, the kind of geology I DO care for can be summed up in this description of my MSc research. My MSc concentrates on the origins and chemical/isotopic make up of refractory inclusions in CV carbonaceous chondrites. Or in less-specialised words, I’m studying how the oldest minerals in the solar system formed and what the environment in space was like when they did.

Below is a picture of my very first mounted meteorite sample (not as dirty as it sounds);

The white bit in this picture is 4.5672 billion years old. It’s one of the oldest solids in the Solar System and dates back to a time when the Sun was just kicking off its fire-juggling party. The minute concentrations of iron in this rock and the iron in your blood are from the same star-derived reservoir. But I digress.

This is a sample of a Calcium-Aluminium rich Inclusion (or CAI) from a carbonaceous chondrite (stoney-iron meteorites). These things formed in a very hot environment, and the minerals within have gone through between one and three stages of melting. The heat inherent in the environment was not due to the sun, but radioactive decay of unstable isotopes such as 26 Aluminium (Half life of ~703 Ka).What I’m doing with these tiny inclusions (which are all less than 10mm in diameter), is determining the major mineral constituents, of each of those I’m looking at the minor or trace element concentrations and finally dating them by determining comparative ²⁶Mg deficits (if any). So what’s involved in each step?

Step 1: Mineralogy: Using an Electron Micro Probe, I am able to determine the major elemental weight percentages of each mineral “phase” of the targeted CAI;

Each shade of grey in the above image is a different mineral. In this case, the lightest phase (Phase 1, points of sampling are orange) is melilite, the second lightest (Phase 2, coloured blue) is pyroxene, phase 3 (in green) is anorthite, and the nearly black phase 4 (in red) is spinel. The above image is an electron back-scatter image of a Type B1 CAI from the carboneceous chondrite NWA 2364.

Step 2: Trace Elements: Using Laser Ablation Inductively-Coupled Plasma Mass Spectrometry (LA-ICP-MS), I am determining the concentrations of 34 chemical elements that are present to an accuracy of a few parts per million (ppm) or less. The elements I’m looking for range through Uranium, Thorium, Lead, Titanium, the Rare Earth Elements (REE) and more. By comparing the concentrations of these elements in different CAIs, whole meteorites and planets, you can get an idea of what was around when each formed and how the areas of formation differed in their respective elemental composition. Did the Earth and these CAIs form in the same place in the solar nebula? The answer at the moment is no, so why did the solar nebula cloud have differing concentrations of elements from one point to another? That’s the big questions relating to how these various bodies formed.

I like to think of this step as a real life game of Asteroids, with a scientific slant.

Step 3: Magnesium Deficits and Dating: Using another kind of ICPMS, namely a Multi-Collector, I will be determining the concentrations of the isotopes of magnesium (Mg) in each of my collected samples. As I mentioned previously, these samples were heated by the decay of ²⁶Al. This particular isotope decays to ²⁶Mg. So the more ²⁶Mg in a sample, the older it is. Any deficit in ²⁶Mg compared to that of the maximum found in CAIs can be correlated to the time between CAI formation and the formation of whatever you’re looking at. So by getting the ²⁶Mg/²⁴Mg ratio from these samples, I can determine their relative ages from oldest to youngest. This is of interest because knowing over what time span CAIs were forming can help you determine whether it all happened at once in a very short time span (and was thus stopped by some process of the sun’s formation), whether there were several exclusive periods of CAI formation (perhaps by injection of ²⁶Al from nearby supernovae), or whether it happened slowly and steadily over 6 half lives of ²⁶Al (most likely).

Why does this count as geology? Well it’s more analytical chemistry. But knowing what was around when the Earth formed and thus what it is made of (i.e, how the chemical composition of the solar nebula changed over time) and how old it is in comparison to other bodies in the solar system, you can build more accurate models of the chemical composition of the materials that make up the crust, mantle and the core of the Earth. This helps in the understanding of how and why things are the way they are. It also makes up the underpinning of mantle geochemistry, volcanic petrology and chemistry, and environmental and atmospheric evolution (which links to the formation of life (abiogenesis) and the like.

In Summation
Geology is broad, and the other posts present in the Accretionary Wedge will surely show this. From dinosaurs to meteorites, sediments to earthquakes, there’s something for everyone in geology, so long as they’re interested in science. If I had to choose a science above all others, geology would be it, because geology is all science.