August 4, 2012
Build your own jake staff!
A Jacob’s staff is a meter stick used for field surveying. They vary in size and shape. Formal ones are often a meter and a half and accomodate a compass mounted on top. I prefer an informal jake staff design. I like mine to be about a meter and round, with jaunty red stripes. This size is excellent for pretending to be leading a parade or marching band or circus while trudging through the field with a pack on and one field assistant with, hopefully, a good sense of humor.
This is my first international expedition, and the first time I’m flying to my field site. My office mate Lydia made an amazing travel jake staff that screws together like a pool cue. It’s the envy of the paleolab and she lent it to Liz, who’s off adventuring, before I could ask. Drat! So I had to make my own simple last minute version.
A jake staff is especially handy for “measuring a section”. We approach a pile of rocks as a series of layers laid down through time. To get an idea of how much time, and in what conditions the material accumulated, the first step is just to measure and descibe the rocks themselves. Then we look closer and closer – until we’re looking through a microscope – at clues in the rock. So a handy jake staff is marked off in 10 centimeter stripes.
I got some 3/4 pvc and a male/female screw end adaptors. The clerk at Home Depot was kind enough to cut it for me. Next, a t-square to mark off the intervals, some red electrical tape, and little rubber nubs for the ends. My labmate Scott sold me on the rubber nubs – it’s fun to toss the stick and watch it bounce away from you when you’re frustrated. Plus the rubber nubs are easy to replace and prevent wear on the staff itself. The finished staff, with my dog Giligan for scale:
And of course it comes apart, so it can slide into my carry on luggage:
Well that’s it for the night. More work tomorrow! Microscope time in the morning! I’m guessing I’ll dream about field work tonight.
Little details. Today is full of them. I’m under the impression that I’ll do better at altitude if I boost my cardiovascular health. Usually I spend much of May and June in the desert collecting fossils and hiking between canyon outcrops. Whoops. This year I stayed home to work on a quantitative project, so I’ve been indoors and sitting in front of a computer for months! With two weeks til the trip, I decided to get in shape the fast and “fun” way: scaling the Baldwin Hills Scenic Overlook staircase three or four times a week.
It’s a surprisingly happening spot here in south central los Angeles. From the top of a 340 foot staircase, you get a nice view from downtown to the beach, with USC and my neighborhood as a bonus. Weekend days, weekday mornings and evenings, the stairs are packed with people of all shapes and sizes; it’s nice to see angelenos getting some exercise. Plus, it’s pretty humbling to be catching my breath and slowly plodding when a four year old suddenly jets past me. After two weeks of this and some yoga, I’m feeling a little more human. Not that I’ll be racing around in the Andes, but I should at least be able to keep upright.
We often joke that it’s easy to hike if we have rocks in front of us. It’s so true! If I need to climb up a mountain, or a canyon, or a hill, I might look at the top and trudge along. If I have some rocks in front of me? If those rocks might contain the fossils I’m looking for? If those rocks there – just another ten feet – just five more feet – just! I get going pretty quick. So here I’ve been, in Los Angeles, and the faster I climb the harder my brain is trying to interpret the “rocks” on these darned stairs. Layers of concrete, layers of gravel… It will feel amazing to have actual 200 million year old rocks under my feet – and in front of my face – once again.
In the past when Dave and I have met to discuss my research, I’ve often been overwhelmed by the immensity of the tasks ahead. To many canyons, too complex of mountain fault systems between them, two many fossils, too many questions. Dave would lean back in his chair and say, “Remember last month when we were at Eagle Mountain, how far we got from the suburbans once Frank said which fossil to search for? This project is just like that. I’ve had students who look at the top of the mountain and they never can start. They just stand there saying, ‘You want me to go up there!?’ But if you just take it one step at a time…” And he’d convince me to write a proposal, or an abstract, or a paper.
Now here I am. Last year of grad school. Near the top of the dissertation mountain. It feels pretty good.
Talk is cheap, though. Ask me how I feel about this next week, when the mountain is real, and it’s in the Andes.
August 2, 2012
I’m going to Peru to see if its fossils are similar to the ones I’ve found in Nevada. I may as well tell you a bit about how we work, and what I found in Nevada. Plus, it’s nice to think about Nevada fossil hunting while I’m stuck in this sweltering Los Angeles laundry mat this morning.
The rocks are only going to tell you what the rocks are going to tell you.
This simple fact of paleontological field work best characterizes our challenge in science. It would be easy to say, “I’m going to determine what happened to bottom-dwelling marine animals after the mass extinction by studying Early Jurassic fossil crabs.” Answering this question with fossil crabs would be difficult, however. Crunchy though they are, crabs’ delicate exoskeletons often get smashed as layers of seafloor muck transform into sedimentary rocks over tens, thousands, millions of years. Consequently nice fossil crabs are rare, and if they occur sporadically in great numbers, one needs to wonder what particular conditions set that pile of crabs apart from others.
The rocks are only going to tell you what the rocks are going to tell you. So, in lieu of fossil crabs, one could look for fossilized burrows made by crabs, shrimps, and similar animals. Fossil burrows can be preserved in rocks surprisingly well. From them we can ask general questions. How did the size and abundance of burrow-makers change during a certain part of earth history? Did the diversity of types and shapes of burrows change?
My advisor Dave Bottjer is well known internationally for his extensive work on fossil burrows, “trace fossils”, and what they tell us about both specific environments and grand transitions in global biology. Here he is on a beach in San Diego, showing our paleo class some gorgeous burrows – small disturbances in the otherwise nicely layered yellow sediments.
I hit a wall early in grad school. A very large wall. Here’s a picture of me standing on it.
This cliff is made of millions of years – about two million years – of rock formed from compressed seafloor muck. I went to this particular cliff to study bottom dwelling shelly fossils. “I see some pretty large snails right after the mass extinction, which is surprising. What happened to the mollusks? How did size change in snails in the aftermath from the mass extinction? Was it gradual or sudden?” I spent some time in the field asking this question. I examined the layers of rocks, made microscope slides of them, and hunted for fossils. Sure enough I found plenty of snails – and scallops and corals and clams – but not until about 2 million years after the mass extinction. What about earlier in the Jurassic? Where the heck were all the snails?
Apparently these rocks were not going to tell me much about snails. I did find burrows though! Yes, plenty of burrows. The kind made by small shrimps that build big dividing chambered tubes deep in the muck, burrows named, “Thalassinoides”. We name the burrow because we’re rarely sure exactly who made it, but different distinctive burrow characteristics can still be tracked.
During my first years in grad school I learned how to ask the rocks different questions. For example, when burrows stand open, they can become filled with sand and bits and pieces of other fossils that sweep across the sea floor. The shrimp-like burrows I found in Nevada had a distinctive black, glassy color. Chert. That’s a rock made with tons of silica – basically it’s rock made of glass or infused with bits of silica and oxygen – the parts that make up glass and the mineral quartz. When I looked at microscope slides made from cross sections through the shrimp-like burrows, I found tons of tiny fossils! They look like little donuts and tubes.
Sponges are filled with tiny glass needles – silica again – which usually fall apart and toss around in the sediments after the sponges die. My shrimp-like burrows were filled with microscopic sponge bits! So that meant there were a ton of sponges around at the time – enough sponges that their microscopic bits filled burrows covering the seafloor for over a kilometer. Those layers of burrows became handy – I followed them in different canyons, different cliff faces, and used them to tell me I was in the right place.
It wasn’t until my third field season that I got a big break. My friend Yadi and I were following layers of storm-smashed snail shells, trying to determine which way the current was heading. When ancient storms kick up shells on the seafloor, they spread them across the deep, making a nice marker of an instant in geologic time. We kept finding odd mushroom and blob shaped cherty knobs interrupting the storm deposits. It finally dawned on me, what if there were some sponges standing on the seafloor that didn’t get smashed? What if they didn’t all get obliterated by storms and time?
The next day Yadi found them. Sponges. Beds of the seafloor life frozen in time, showing clusters and bunches of small sponges nestled together with a few scallops. We couldn’t believe our luck. Sponges rarely preserve such nice fossils – and to see the actual seafloor snapshots!
But we’re cynics, Yadi and I. We couldn’t quite believe our eyes. What if it was just an illusion? That day we decided to cut the trip short. We packed up our best samples of potential sponges, drove back to California, and started analyzing them that night in the lab. Over the next two days we poured acid on them, made microscope slides, and looked at pieces of sponge under the Scanning Electron Microscope. There was no question. These were fossil sponges. A week later I was back in Nevada with my sidekick Amir, and we found their friends – the whole damned mountain is made of sponges!
The rocks are only going to tell you what the rocks are going to tell you. Sometimes I go out to find snails, and I find sponges instead! This sponge story goes deeper – and it goes around the world. But this is enough for one blog post and my laundry’s almost dry. Next time I’ll tell you why we’re going to Peru and what we might find. But I’ve got to remember, even the rocks in Peru are only going to tell me certain things, and I don’t know until I go look.
“Oh, shoot, is it after midnight?” I blink at my computer. I check the calendar. ”Oh. Shoot. Is today the SECOND? of AUGUST?”
Life as a grad student. My mother tells me I’m in training to be an absent minded professor. It’s not that I’m absent minded, exactly… it’s just that I rarely know what day it is. I should explain.
I’m going to Peru on Monday. Monday. Today is… Thursday. That leaves very few days to, say, regain conversational spanish. I also need to do laundry, wash the dog, and order some cool bugs stuck in amber for the undergraduates to look at. When I get back from Peru, school starts.
The most outrageously valuable commodity to a grad student in my position is uninterrupted time to think. And BOY have I been thinking. I actually woke up this morning convinced that the statistical results I’d dreamed about were publishable because dreams are random and therefore unbiased. I read textbooks over breakfast; I draw diagrams on the train platform; I write code in my head while I walk the dog.
Two hundred million years ago the super continent Pangea split apart in a fiery mess of volcanoes. Resultant climate and chemical changes were bad news for any marine animals who wanted to keep the shells on their backs. In the sea, the global mass extinction event was even worse than the more famous time all those dinosaurs died.
I want to know what happened afterwards. If I were a snail, or a sponge, or a crab, living on the seafloor in the earliest Jurassic period, what was the ecological scene? Did life bounce back? Were ecosystems dominated by one particular group? What if I were an ammonoid, a shelled squid? Would there be other swimmers in the water? Drifters? Who were the winners and losers as life rebuilt?
As a PhD student at the University of Southern California I get to tackle these questions the fun way. I go to the desert where rocks record layers of marine muck laid down in the Jurassic seas, and I look for fossils to answer these ecological questions. People always ask me, “Do you go on digs?” Mostly, I hit rocks with a hammer. I carry a little whisk broom and brush things off. My favorite places have few animals and fewer plants, so the rocks are exposed under a clear sky, ready to share their secret history.
But, as my advisor Dave always likes to say, “The rocks are only going to tell you what the rocks are going to tell you.”
That is hands-down the most crucial instruction of my grad school career. The only hard part about what we do is deciding what rocks, and how to ask. The rest is high adventure and midnight oil.