Earlier this week, I showed you how scientists can use a simple, hand-operated tool to collect stratified core samples of mud at the bottom of a swamp. The deeper the samples go down, the older the mud is—until, eventually, you're looking at 6000-year-old muck, the remains of a lake bed that filled in with sediment and became swamp.
The core samples are narrow logs, each 50 cm long. (In all honesty, they looked like less-colorful versions of the 3 pound gummi worm I ordered for my 30th birthday party last year.) For the most part, they're some variation on the shade of brown, with occasional streaks of red and burnt umber, until you get to the very bottom. There, the samples turn grey. Put a bit in your mouth, as I was encouraged to do by Harvard Forest director David Foster, and you'll taste clay and feel grit between your teeth.
That's all well and good. But what do you do with core samples once you have them? For this installment of Dispatches From Harvard Forest I'm going to leave the woods and head into the lab, to see what happens to the parts of the Forest that scientists take home.
Step one: Make dirt cupcakes
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I spent last weekend in the Harvard Forest, participating in hands-on science experiments as part of the Marine Biological Laboratory's science journalism fellowship. The goal was to give us an inside look at what, exactly, scientists actually do. When you're reading a peer-reviewed scientific research paper, where did all that data come from?
Sometimes, it comes from a swamp.
On Saturday, we walked into the Forest's Blackgum Swamp to take core samples out of the muck. There was no standing water in this swamp, at least not when we visited. But I wouldn't call the ground "solid", either. Instead, it was more like a moss-covered sponge. With every step, the ground beneath me would sink and smoosh. In some of the lower patches, that meant a shoe-full of water. In other spots, it was just a disconcerting sensation.
Taking core samples involves a little machine that's like a cross between a shovel and a straw. Made of heavy, solid metal, it has an extendable handle on one end. At the other, there's a hollow, cylindrical chamber that can be opened and closed by turning the handle counterclockwise. You drive the chamber into the ground, turn the handle, and then pull it back out. Once everything is back on the surface, you can open the chamber and see a perfect cylinder of earth, pulled up from below. That cylinder is removed from the chamber, wrapped in plastic wrap, labeled, and put in a long wooden box. Then you do all of that again, in 50 centimeter increments, until you hit stone. We got to about 475 centimeters—15 feet deep. By that point, you'll have collected 1000s of years of layered sediment.
This is not as easy as it sounds.
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