However, this week I received an offer on one of the post-doc positions for which I have applied, and suddenly my schedule is far, far busier than it had been. I am still aiming at the same deadline for completing my writing and submitting the final, bound, thesis to the examiners, but now it is *urgent* that it be done by then, so that I may board an airplane and go start my next adventure. As a result, after consulting with my teacher, we have decided that instead of my going into the school to meet the students in person, I would send them a letter, and invite them to e-mail me with questions. Then, in a few months, when I am settled into my new home, I can use Skype to come into the classroom and talk with them about what I am doing in my new job.
For your amusement, here is a copy of the letter I wrote for my school:
Hello, I am a Life-Long-Scholar, and I'm your pet scientist through the "Scientists in the Schools" program. My job is to be available if you have questions about science, and to share with you the fun things I do in science. My particular field is geology--I study the earth, especially the rocks which make up our planet and how they change over time. The rock cycle is an amazing process. You all know, I think, that sand is nothing more than very tiny rocks which have been broken off of bigger rocks, and you have probably seen sandstone, which is a "sedimentary" rock that is formed of sand squished or cemented back into a solid chunk again. The other parts of the rock cycle are harder to see, because they require much heat or pressure to make happen. Just as a liquidy cake batter changes when you put it into a hot oven into a solid cake, so sand and mud change if you burry them deeply enough. A kilometer is deep enough to squish them back into rock, but if you burry them really deeply (15 to 30 kilometers deep!) it gets hot enough for them to start changing. New minerals start to grow, dissolving the tiny bits of sand and mud and growing them into crystals. Left long enough, the crystals can grow to large sizes. This change is called "Metamorphism" (from the Greek word meaning "change"). Rocks that are metamorphic tend to be pretty, because, often, those crystals grow big enough for us to see them, and many minerals which like to grow at those depths tend sparkle, which makes the rock shiny. At even deeper depths than metamorphism the rocks can melt. When this happens the liquid (called magma) tends to work its way slowly back up to the surface of the earth, until it either cools back into a rock somewhere under ground (they call this "intrusive"), or until it reaches the surface and explodes out of a volcano (they call this "extrusive"). Both "intrusive" and "extrusive" rocks that cooled back into stone from liquid magma are called "igneous". The reason we call it a rock "cycle" is because all three of the main classifications of rock types: sedimentary, metamorphic, and igneous, can, under the correct conditions, and given enough time, turn into the others. A sedimentary rock is made up of broken bits of any of the three rock types and then put back together into a new rock A metamorphic rock is made up of new minerals that grew and replaced the minerals in any of the other rock types when it got buried deeply enough to change. An igneous rock is one which is cooled from liquid magma, which first melted from any of the three rock types.
All scientists first choose their general field (do you like plants? space? rocks? animals?), and then they choose more specialized things to study in the field. I am a metamorphic petrologist. This means that I study metamorphic rocks. I "read" the clues in the rocks to learn what happened to make them the way they are today. Some of the clues are physical--when rocks are deformed the minerals which happen to be long and thin (like a pencil) or thin and flat (like a piece of paper) tend to all align themselves pointing the same direction, so from this we can tell from which direction the pressure was applied. Sometimes those layers wind up folding, and those folds give us more information about the pressure which affected those rocks. Some of the clues are chemical. All minerals are made up of chemicals, arranged in a pattern. The pattern can accept more than one chemical element in certain spots, so long as they are close to the same size. Which one happens to be in that location in any given repeat of the pattern will depend on both what elements are available in the rock in the first place, and what the exact temperature and pressure is when the mineral is growing. Some minerals are buddies and like to swap elements, trading back and forth as conditions change. Iron (chemical symbol: Fe) is a little bit bigger than Magnesium (chemical symbol: Mg), but they are sort of similar in size. As a result, they tend to both show up in minerals at matching points in the pattern, but, some minerals have a pattern with more room than others. The ones with more room in the pattern will still have room for Fe when the heat and pressure increases, but the ones with a smaller slot won't. Therefore, when the heat and pressure increases, they swap, the smaller slot takes the Mg, and the bigger slot mineral takes the Fe. But, if the heat and pressure decreases, they swap back again. One of the things I do is measure how much Mg and Fe is present in certain pairs of minerals today, and from that calculate what the temperature and pressure must have been when those minerals were growing.