with understanding one becomes free to explore

I received a comment on one of my AGU highlight posts today which mentioned that “…there are as many as 6, perhaps 10 person in the world who do really understand a-X models”. Given how slowly my own understanding has been building on this topic since I was first exposed to the concept early on in my PhD project, I suspect that he’s probably fairly accurate in his count, despite having offered the number in jest.

Doing the sort of modelling metamorphic petrologists do can be compared to various skill levels in cooking. Some people “cook” by opening a box or a can and following the instructions printed on the label to heat the contents. Others “cook” by looking at a recipe and faithfully performing every step of the instructions in the sequence suggested, with no real understanding why the author of the cookbook wanted them to do step A before step B; but by correctly following the instructions they obtain a result which they are happy to eat. Still others of us decide what we are hungry for, rummage around in the pantry and throw together delicious food that brings us joy to eat, instinctively doing some tasks before others because we understand the manner in which the tasks coordinate to create a perfect dish. We do things differently every time, never fearing to improvise because we understand *why* things work in the kitchen and what things may be changed and what rules are iron-clad.

As a petrologist I’m slowly working my way from the one end of that spectrum towards the other. The first time I attempted to use Perple_X to calculate what phases should be present in my rocks I had no idea what I was doing, or why. My advisor had pointed out a recently published paper which used that tool for calculations on a similar rock type to my own, so I downloaded the supplemental data set, used the “in” file provided, and ran the program using the settings their paper reported them to have used. Low and behold, the program generated a diagram which looked just like the one they had published (open box, remove plastic from tray, put trya in oven at 350 F for 35 minutes).

Thus encouraged, I edited their in file to show the composition of my sample instead of theirs, and ran it again, getting a very different diagram. This marked my first baby step in moving away from heating packaged food to something about on the level of complexity of using a packaged cake mix (just add water, eggs, and oil). Some months passed while I used this technique for a variety of different samples. Then, one day I realized that I needed to generate a different type of diagram, so I began to learn what changes are necessary to do so. This required much reading of the tutorials accompany the program. Not unlike learning to follow a recipe (cream butter and sugar together, beat in eggs and vanilla, add flour mixture alternatively with milk…).

I find that the more papers I read on this topic, the more I understand about the many, many options for calculations available in programs such as this one (there are others out there I should like to try as well, if I can only make the time to do so). It is my hope that, eventually, I will join the ranks of those who understand a-X models and will be able to reach the same stage of confidence in using these as I enjoy each time I enter the kitchen to cook or bake myself something yummy.

The highlight of the AGU meeting (so far)

Yesterday’s highlight for me was, without a doubt, the Bowen lectures. Tim Holland & and Roger Powell have been recognized for their contributions to Metamorphic Petrology for their efforts in the creation of their internally consistent thermodynamic data set and their Thermocalc program which uses that data set to do a variety of thermodynamic calculations and were invited to speak on the history of their research and the directions they see the science going from here. The titles of the talks they presented are: Calculated metamorphic phase equilibria. Applications and strategies for equilibria in high pressure rocks (presented by Tim) and Activity-composition relationships in the forward modeling of metamorphic phase equilibria (presented by Roger). While I found the science part of the talk useful and fascinating, the part I’m going to write about today is my reaction to passing comments made during their talk. Tim shared a photo of himself doing field work for his PhD project in the Alps in 1979, and commented that this award is generally awarded to “mid-career” scientists. By my math that means their career should continue to be active through the year 2039. Roger’s talk included the fact that the bulk of the creation of the internally consistent data set is, by necessity, the work of a single individual (Tim), while the coding for the programs they’ve developed is, likewise, primarily the work of a single individual (Roger), but that both tasks are immensely facilitated by the many hours of discussion on the topics they’ve shared over the years (I’m seriously paraphrasing here).

The combination of these comments prompted me to wonder what arrangements they’ve made for the continuation of their work when they are no longer able to continue. Are they training their students to continue to expand the data set? Is there someone out there who is able to continue to refine the coding of the programs as new information is available that suggests potential improvements? Since I didn’t actually get to meet either individual, I didn’t have an opportunity to ask, nor, do I think, would it be the most appropriate of questions. I do know that they’ve delegated the maintenance of the Thermocalc web page therefore it wouldn’t surprise me if they have other collaborators working with them to keep their tools growing and accessible into the future, even if they decide to retire at some point.