Wednesday, February 27, 2013

luckily, my geo-injuries have been minor


When I first saw the call for Accretionary Wedge 55 I couldn't think of any injuries I had gotten in the field, and closed the tab on my browser and thought nothing more of it. However, today, reading some other reports of minor injuries, I suddenly remember a rock-related owie.

I was an undergraduate geology student, living in southern Oregon. My boyfriend at the time decided that since I liked rocks and was new to that part of the country he should take me on an adventure to the Lava Beds National Monument to do some caving in the lava tubes there.  As far as dates to take geologists go, this was a very good idea.

So there we were, wandering through a lava cave, the only light coming from my headlamp and his flashlight. He scampered up a small pile of lose rocks, each perhaps 10 to 20 cm in diameter, and I started to follow. However, in so doing I discovered that the density of vesicular chunks of lava is very different from the more solid rocks I had encountered elsewhere, and as a result they rocks shifted under my feet in a very unexpected manner.  I lost my balance and fell forward, catching myself on my hands.

In the process the little finger of my left hand got caught between two rocks. When I called out, more in surprise than pain at that point, my boyfriend returned to my side, asked to look at my hand to see if it was ok, and, seeing that my little fingernail had split lengthwise, and that the outer portion was pointing off at a wrong angle, decided that the time to fix it was before I noticed that it hurt, so he grabbed my hand and pushed the nail back where it was meant to be. That got me to exclaim in pain!

That pretty much cut short the adventure part of the day—instead of exploring further we went back to the visitor center, cleaned the wound and got it bandaged up.  Thanks to his prompt re-alignment of my finger nail the wound healed cleanly, and I never lost any nail, though it had a bit of a seam running the length of it for a few weeks.

Tuesday, February 19, 2013

Book Review: Metasomatism and the Chemical Transformation of Rock




Last April I heard about a soon to be released textbook that sounded very interesting and useful to my current research project: Metasomatism and the Chemical Transformation of Rock, edited by Daniel E. Harlov and Håkon Austreheim (published by Springer).  I checked out their web page, and saw that it would be possible to obtain a copy for review, so I filled in the form and sent it in.  In September I received an email letting me know how to access my copy on line, and I have been happily reading my way through the book (in between my other duties) ever since.  Now that I have (mostly) completed the reading, it is time to sit down and type up the review.

First of all, I am pleased to note that sometime between when last I read a textbook and picking up this one the fashions in how they are organized seems to have changed—this book starts with a chapter that summarizes what can be found in all of the subsequent chapters. I think I like this new trend, since it makes it easier for a busy person to decide which chapters they actually need to read based on what is and is not relevant to their own research.

The introductory chapter also provides a concise, clear, definition of metasomatism and an explanation of how it is both related to and different from metamorphism.  Metamorphism refers to the changes in rocks due to changes in physical conditions (primarily heat and pressure) which may or may not involve a change in composition of the rock. This is a subject I am well versed in, having done metamorphic research in one form or another for more than seven years now. Metasomatism, on the other hand, refers to changes in the composition rock due to interactions with an aqueous fluid, which picks up some elements and deposits others.  This is clearly related to metamorphism, but while they overlap, they are not the same.  It is also the major process affecting the rocks in my current research area, which is why I was so happy to see the book come out just now.


For the most part I have been very happy with this book—it takes a variety of different threads and ties them together in an easy to understand package.  Indeed, I have so enjoyed some of the discussions that I have taken longer to read the full book than I might otherwise have, since I stopped so often to look up and read references cited—something I don’t recall ever doing when I was an undergraduate student reading textbooks because they were required for a class.  

The list of chapter authors includes names that will be familiar to anyone who has been reading papers that address aspects of metasomatism (see above link for the table of contents). My personal favourite chapters were the ones on thermodynamic modelling, the effects of metasomatism on their host rocks, and on geochronology.  I found the one on thermodynamic modelling fascinating since I am already familiar with doing that for metamorphic rocks, and it was interesting to read about what needs to be considered when one assumes that the bulk rock composition DID change, as it does with metasomatism, but as it does not (necessarily) do with metamorphism. The chapter on effects is particularly useful for me because this is information I need for my current research, and I enjoyed the geochronology one because I did a fair bit of geochronology for metamorphic rocks for my PhD research, and it is interesting to see how one approaches it differently for metasomatic environments.  

I did notice some minor issues with the editing on a grammatical level, which surprised me, since I would have assumed that a major publisher would have good editors on staff whose job it is to prevent such things. They were just little things that caught my eye and grated a bit on my nerves as being awkward and clunky (I think that the phrase "…presence or not of fluids" should have been written "…presence or absence of fluids”).  However, such details do not actually detract from the content, which I am finding to be very useful.


I am also pleased to pass on the news that the authors of this book have recently presented a short course at the 2012 Goldschmidt conference.  They have shared the pdfs of their presentations for this course on line.  I would have loved to have attended the workshop, but since I wasn’t able to make it to the conference I am delighted that they have this handout available—it appears to compliment the book very well.


Friday, February 15, 2013

Three broad roads a geologist might travel during their career



There are several different paths a geologic career might take: academia, exploration, or environmental/risk. Which one is best for you will depend on your personality type.

A geologist in academia is usually someone who studies rocks to better understand the information recorded in them—how and why did they achieve their present composition and/or configuration?  They start with what they know: the rock is located here and looks like this, and extrapolate from clues within the rock to determine how it got there, and why, and when, and what happened to it along the way.

An exploration geologist, on the other hand, is looking for something (often oil or mineral resources).  They don’t know where their commodity is located, so they study locations where similar such resources have already been found to look for patterns to the rock structure and/or composition that they may be able to recognize elsewhere and so find what they seek in a new location.

The third category of geologists the environmental sector and/or risk management.  Their job is to understand the dangers which are present in our world, and look for ways to prevent those dangers from becoming problems.  They start with the facts that are known (e.g. the presence of contaminants in the ground water at point A, zones of weakness in rock that could lead to landslides, or the location of an active fault or volcano) and play “what if” games to determine how much (or what manner of) danger these present to the people in those areas.

So, which are you? Are you more interested in asking question of “how/why/when”?  Do you want to know “where”, or are you more concerned with “what if/how can I help”?

For myself I am pleased to be in the academic track—I want to better understand the world around me. I am not interested in playing games of hide and seek—I don’t even care to go shopping because I don’t enjoy trying to figure out where to find something I need is located.  Often the stores don’t even carry what I want and I waste valuable time looking for it, a parallel which is probably all too familiar to exploration geologists—not every search they undertake leads them to a discovery.  However, I suspect for those who do enjoy a good search there is an extra reward in terms of satisfaction when their work does lead them to what they seek.  

I am also far more interested in understanding how the rocks got to where they are now than I am in understanding what dangers they present to humans.  While I am very aware that it is vital that someone is working to keep contaminants out of ground water, or tracking them once they are there so that no one is using the bad water, I don’t want it to be me.  While I am grateful that I know enough not to build my house right on top of a fault zone or in the path of a potential landslide, I don’t wish to be the one who has to warn others about these dangers.  Adding in a human element presents all kinds of extra challenges and complications that I am happy to leave to others.  But my biases are not yours, and you are likely to have different interests and different reasons to find one of these paths more or less appealing than the others.