Tuesday, August 26, 2008

Connecting Microscopic and Continental Scales

This month’s Accretionary Wedge is on the topic of “connections”, which is a terribly appropriate topic for geologists, since everything is interconnected in this universe, and we (generally) study that portion of the universe which we call “Earth”. The planet itself is a ball made of up a variety of layers some of which, over time, do a bit of mixing up. They call this mixing “plate tectonics”, which theory has been around in a changing, but reasonable stable form since I was a child, and existed in a much earlier form (as early as 1915) called “continental drift”. The theory of plate tectonics is a very inter-connecting, unifying theory which helps explain the current distribution of continents around the planet, which parts of the continents (and the ocean floor as well) are wrinkled into mountains (and how the relative motion between two “plates” causes that wrinkling, either in the form of very high mountains when two plates “crash” into one another (e.g. the Himalayas, where India is colliding with Asia) or in gentler mountains where they are sliding past one another (e.g. the San Andres Fault).

Plate tectonics is also useful when looking at rocks, like those I’ve been studying for my PhD project (see photo in my user pic!), which, while at the surface of the earth today, have evidence that they were once buried quite deeply. Every mineral has its “favourite” temperature and pressure—the conditions wherein it will grow, given enough time to do so. Many minerals have a range of compositions, and they will vary their composition based on the temperature and pressure under which they are growing. Garnets will swap in magnesium (Mg) and out iron (Fe) at the same conditions that biotite swaps in iron and swaps out magnesium. This exchange has been studied extensively, going back to the 1970’s with experiments involving putting a tiny amounts of biotite in with large amounts of garnet (and vice versa) with known amounts of Fe and Mg into tiny containers which they then squished (that’s a technical term) with lots of (a known quantity of) pressure and high heat for an extended period of time. Then they checked the mineral which was present in smaller quantity to see how its quantities of Fe and Mg had changed. Doing this a number of times at different conditions permitted them to work out how much iron and magnesium each mineral prefers at a variety of pressure-temperature combinations. As a result of such experiments and comparing them with the proportions of Mg and Fe in biotite and garnet in real rocks, we now have a method of working out just how hot and how squished (how much pressure) rocks must have been to grow the minerals they currently have. This helps us work out the details of the past configurations of the continents—it is known how deeply something must be buried to reach a given pressure, so from the composition of the minerals we can figure out how deep the rock used to be, and therefore what its prior plate tectonic setting would have been. It is all interconnected, from the microscopic level to the scale of an entire continent!

Sunday, August 17, 2008

How I became a Geologist

Even as a small child, I never wanted to have a job. To me “work” was a terrible thing which caused people to reply: “No, sorry, I can’t, I have to work.” when asked: “will you be attending this super-fun-upcoming-activity-you-wouldn’t-want-to-miss?”. But I loved going to school—learning new things every day was fun! When not at school I generally had my nose in a book, unless I was outside admiring the beauty of the mountains, or exploring the woods near my home.

Over the course of a couple of summers I watched a small stream change its course as a bend in the waterway around a peninsula met itself, causing the peninsula to became an island, and then the island was abandoned as the water chose the shorter, straighter course in preference to the longer loop around it. Years later, in my first Earth Science class, when the teacher reached the part about how rivers meander and change their course I was excited to realize that this was something I already knew—my own observations had already revealed it to me. I think that this may have been the first time I realized that what I learned on my own, through my own observations, was every bit as valid as the “official stuff” that was presented to me via my teachers at school, and indeed, the things taught in school were all based upon *someone’s* observations! Science is really, naught more than the collected and organized observations of thousands of people. Observations made at every scale imaginable—from the tiniest microscopic investigations to seeing patterns in the outlines of the continents. It all meshes together to create a wondrous whole, if one knows how to look for it.

So once I completed high school I choose to, in part because of my above mentioned quest to “avoid working”, enrol in a University, intending that I would “be a student forever”, and just spend my life taking classes. Somehow, although I had heard the phrase “PhD”, I didn’t really realize that classes were only the beginning of University in general and Science in particular. So I took classes. Lots of classes! In many topics—introductory courses like Chemistry, Eastern Philosophy, Algebra, Computer Programming, Mountaineering, Norwegian, Modern Dance—more advanced courses like Medieval Literature, Chaucer, Old English. Years slipped by while I was having fun. Due to a variety of personal reasons I moved a couple of times, so my credits piled up at a several different schools, yet still I persisted in the dream of “being a student forever”—taking classes was what I knew and what I loved to do.

Sometimes people hearing this odd goal of mine would say things like “if you love school so much, you should be a teacher”, but I would shake my head and point out that it is much easier to write one essay than it is to grade 25 of them. Throughout this period, since I had no intentions of ever “graduating”, I paid no attention to what the requirements for graduation were, and never looked into truly advanced study in any one field. Even the “advanced” courses (designation based upon the course numbers assigned to the classes) I took were things I could easily take without worrying about things like “prerequisites”.

Then one day, one of my friends with whom I’d attended high school was wondering which of the graduate schools *offering him money* he was going to accept. Now *that* got my attention! You mean they are going to *pay* you to go to school?! How wonderful! At that point I was a live-in housekeeper to earn my room and board, and earned my tuition by working registration at the University each semester. I was getting by, but only just. Suddenly, I had a new goal. Rather than “never graduating” and “being a student forever”, I could “graduate”, and then “get paid to be a student”. But studying what? The problem with the whole “graduate school” concept is that they expect you to “declare a major”, a field of speciality. There were so very many interesting things available to study! How would I ever choose between them? So I consulted the course catalogue of the University at which I was then enrolled, and looked at the classes required for graduation in each field. As it turned out, *every* major available at my University required at least one class which sounded interesting, but also required at least one class which did *not* sound interesting! Hmm. This complicates things—I didn’t wish to be “forced” to take a class which didn’t interest me.

Around about that same time I was enrolled in a class called “Elements of Physical Geography”, taught by a Geologist. The teacher was a good one, who maintained class interest by frequently telling us stories which began “Geologists are stupid, we do things like…” and then he would tell us how close he got to Mt. St. Helens before it erupted while he was working with the machines which monitored the mountain’s current conditions, or he would tell us about other adventures, in the name of science, that people he knew had undertaken. Yes, he did say “stupid”, but I heard “fun”—without exception every story he told held my interest, I could picture myself doing things like that—having fun, risking (minimal) danger, and learning things in the name of science!

Back to the course catalogue I went—look, Geology wasn’t even an available major at my University! Undaunted, my research continued; clearly it was time to go look at other course catalogues from other universities. Hey—look! *Every* class that this University requires for their Geology Majors sounds like fun! Check another University—yup, every single class that they require of *their* Geology Majors sounds like fun too! Six years of being a full-time University student, and I’d finally found the course I wished to study! Very little time elapsed from that moment until I’d applied and transferred to another University, in another state, and became a Geology Major. The classes I took there were, in fact, as much fun as they sounded like they would be from their descriptions, but that will have to be a post for another time…