Thursday, October 9, 2008

Geology analogies (hey, that would be a cool name for a rock band)

Get it? Rock band? Ha. I'm just full of punniness today.

Bad jokes aside, the real reason for this post is in response to Callan's question, "What are some of your favorite analogies for explaining geological concepts to other people?" As a TA for an intro geo lab, I'm finding that I use analogies a lot, because most people don't have much of a background in the geosciences. (Despite it being on some sort of standardized test they do here in NY in high school, which I find a little disappointing. More emphasis on geology!)

Most of them are pretty simple things. When I was talking about why it's important to be systematic and detailed in writing rock descriptions, I compared it to describing how to find a car in a mall parking lot. Saying, "It's the blue Camry" is pretty useless, since scads of people have blue Camrys. But saying, "It's the navy blue Camry with leopard-print seat covers and hot pink fuzzy dice and the My kid can beat up your honor student bumper sticker on the back" is much more useful (not to mention an indicator that the owner of the car has a serious lack of taste). Likewise, saying that a rock is "pink and white and sparkly" doesn't tell me much, but saying that the rock has "fifty percent 1-2 cm size pink crystals, thirty percent .5-1 cm size white crystals, and the rest is equal amounts .5 cm size clear and black crystals, and they're all interlocking", tells me a lot (and leads me to think that the rock is igneous, and most likely a granite). It's also a way to impress on people that they don't need to know what they're looking at to describe it accurately; I might not know anything about how a car is put together or how it runs, but I can tell you what it looks like.

My mother actually helped me come up with a food-related one. Every so often she likes to try out a bunch of new cookie recipes, and she found one for striped icebox cookies. If you make them with two colors/flavors, they look like this:

I think I was discussing something geology-related while she was slicing them (basically, you make the dough, stack strips of the alternating colors, and then slice the cookies off the resulting "logs"). A few cookies toward the end were messy, and she stopped to look at them for a moment. "What if I do this?" she asked, adding a few extra slices and smashing the pieces back together. Which resulted in something that looked like this:

Fault cookies! (I love my mom. She made plate tectonics tasty.) I don't think I'll have a chance to use this one in lab, but it's good to keep in mind for later teaching opportunities.

Then there are all the volcano related ones. Lava domes are squeezed out of a conduit like toothpaste; volatiles exsolving from a melt are like bubbles in a bottle of champagne; and the old formula of Silly Putty is apparently a great way to demonstrate brittle/ductile transitions if you smack it with a hammer. (It's also a good way to injure people, so make sure to have goggles on hand.) I can't remember anything that I've used to describe things to people, but I'm sure I'll get to that when I start trying to tell my family what I'm doing for my thesis.

(I also really love the analogy that I saw at a Geological Society of Washington meeting last year - Callan wrote about it here - where the similarity of volcanoes and coffeemakers was discussed in terms of eruption dynamics. Can't take credit for it, but I still want to try that out - perhaps during a late night lab session would be best.)

5 comments:

Callan Bentley said...

Awesome. Love the car-in-parking-lot analogy.

C

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Jerry D. Harris said...

I find myself using food analogies a lot in teaching geology -- food is great because students can usually relate to it firsthand, and because various foods mimic geologic processes in nice ways. One thing I've been thinking about trying to demonstrate is using brownies to demonstrate transform fault motion, and how it can create small blocks that rotate between the main plates (like what's going on with the San Andreas) -- I figure that a semi-moist brownie, if sheared to create transform motion, should generate little crumbs in the "fault" that are rotated and dragged around when the brownie halves are slid past one another...

Julian said...

...holy crap, I want fault cookies!

I also love the car analogy.

Renee said...

My mineralogy teacher, a really cool chick from Ireland - I study in Amsterdam, Holland - explained crystal structures with sandwiches (how the tetrahedra and octahedra are stacked in layers on top of each other).

She also brought a bag of Maltesers and a bag of M&M's to one lecture, to explain anisotropy of minerals as well as to eat them :)