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Episode 5: How Do We Dig up The Bones?


Welcome back to the New Jersey State Museum’s Ask the Experts Video Learning Library, where we’re digging into some of the most common questions people ask paleontologists about what we do and how we do it.

So far we’ve shown you how to look for, find, and identify fossils, and how to begin the excavation process. Last time you joined us we were at our dig site uncovering fossils and mapping the bones as they lay in the ground. Now it’s finally time to get those bones out of the ground. Can we just start picking away at each bone?  How do we do this safely so that we don’t damage the bones, or ourselves?  Let’s break out the tools and start digging into those questions right now.

Anyone can just yank these fossils out of the ground, but doing so would put them at great risk. These fossils have been here in the ground for almost 70 million years, so they’re incredibly fragile.  And every fossil is very important, because they all holds clues to the lives of these animals lived and the environment they lived in. It’s our job, as responsible scientists, to get them out of the ground as gently and carefully as possible.

The first step is to stabilize any exposed bone and to clear off the site just enough to see how the bones are lying in the ground. Then we’ll take as many notes and photographs as we can to collect lots of data, that will be very important to us later on.  Once that is done, the next step is to dig a trench around the area we want to excavate. You may notice here that we’re using some pretty big tools.  A general rule in paleontology is that the closer you are to the fossils, the smaller the tools, and that’s so you don’t risk damaging or destroying them. We want to dig the trench far enough away from the actual bones that we can use these picks, shovels, and geology hammers to break up and remove the rock. Depending on the situation, we’ve even been known to use backhoes and jackhammers to get the job done, but there’s no way we’re getting that kind of equipment down here so this job is going to be all by hand.

Once our trench is complete, we can start to prepare the bones for jacketing.
We’ll do that by wrapping each exposed fossil in aluminum foil or wet toilet paper. Yes you heard right! That foil, or in this case toilet paper, acts as a bit of a cushion separating  the fossil from the plaster jacket, which will come next. We don’t want the jacket to stick to the bones - that could really damage them later on. 

Finally, it’s time to start jacketing. Jacketing is a messy, but really important process of creating field jackets, which are like a very hard and durable shells that encase and protect the fossils for their long and hazardous journey back to the lab. This is just like a cast a doctor might put around your arm if you broke it. 

Field jackets are made from strips of burlap dipped in wet plaster of paris, and wrapped carefully around the bones. At this point, we can only make a top jacket, so once we get a nice thick layer on the top and sides of this fossil area, we let it sit and dry.  A small jacket might be nice and dry in an hour, but a big one needs a lot more time, and we’ll often let it sit overnight. 

Once the top jacket is dry, we’ll start to chip away at the pedestal below the fossil layer. We’ll even dig tunnels under those bones so we can wrap more plaster strips on the underside of everything.  Once the base of that pedestal is really narrow, we’ll carefully, but quickly flip it over.  We do it quickly so that everything doesn’t fall out of the top jacket, and carefully so that it doesn’t go rolling down the hill or onto someone. Success! That was a great flip, so we’ll just remove a little bit of the excess rock, and now we can continue jacketing on this side. Now we have a perfectly protected fossil and a very tired and messy field team!

Hopefully we’ve wrapped up the mystery of how we get the bones out of the ground and how we protect them for the journey home. Now all we have to do is haul them up there… wayyyy up there… and load them onto our trucks and drive them home. We’ve got a big job ahead of us, but we better dig into that next time. In the meantime, thanks for joining us, and as always, keep digging!