Please Note: This is a draft version of the article accepted for publication in Science & Children.

Digging Science Building a Fossil Pit in Your Schoolyard

  

Searching for hidden treasures has always been an alluring endeavor, whether you are a scuba diver canvassing a sunken galleon for gold doubloons or a child searching through a backyard for hidden eggs on Easter morning. The more the objects are valued by the hunter, the greater the excitement of the hunt. Many scientists are also treasure hunters. For a scientist, the valued treasure resulting from a hunt can range from discovering a new component of a neutron to locating a new star in a distant galaxy. Although these monumental treasures are usually only discovered by established scientists, young future scientists can also experience the thrill of scientific discovery right in their own schoolyards. In our case, the treasure we decided to focus on was locally accessible fossils.

To make the study of fossils more fun and realistic, we constructed a small fossil pit in our schoolyard. With the help of the Florida Museum of Natural History at the University of Florida in Gainesville, the pit was filled with fossil-rich substrate from active dig sites used by the museum. This substrate was then enhanced or "salted" with additional high profile fossils, like giant shark's teeth, contributed by the museum. To maintain the authenticity of our fossil pit, only fossils found in Florida were added to the pit.

A Rationale for Creating a Schoolyard Fossil Pit

The idea and inspiration for construction of the fossil pit emerged while we were teaching an education course at the University of Florida entitled "Science Instruction In Informal Settings." The course explores the benefits of educating students in informal settings such as schoolyards, zoos, botanical gardens, parks, and museums. While field trips to actual study sites are the most realistic sites for fieldwork and scientific investigations, they are also expensive and labor-intensive for teachers. An alternative approach to off-campus field trips is the development of field study sites in schoolyards.

Traditionally, schoolyard scientific study sites include stations for activities such as birdwatching, pondwater studies, soil studies, vegetation studies, invertebrate collection, and meteorological investigations. Although we wanted to incorporate these useful and obvious types of study stations in our schoolyard outdoor learning area, we also wanted to include a station which focused on the fossil history of our school site and the surrounding area. Fortunately we were able to locate an article by Hartman and Dubowsky (1989) which thoroughly described the process they used to construct and fill a two square meter fossil pit at a community college. In their case, the pit was filled uniformly with fossiliferous shale from a local quarry. We decided to construct a pit that was similar in size (6.0 meters long, 4.5 meters wide and 0.6 meters deep) but different in composition. After consulting with Dr. Russ McCarty, a paleontologist at the Florida Museum of Natural History, we decided to try to create a geological time line in our pit. By dividing the pit into three separate sections, each section could be filled with fossils and substrate representing different Epochs of the Cenozoic Era.

The Construction Process

First a centrally located site was chosen on our campus to facilitate its use by elementary, middle, and high school science classes at our K-12 school. The site was also located near a service road to allow easy access for fossil-loaded dump trucks and visitors. Building of the fossil pit began with the excavation of the 0.6 meter deep pit by the University of Florida's Grounds and Maintenance Department. Then a wooden frame and dividers were constructed during a Saturday Parent Workday (see Photo 1).

Like the Hartman and Dubowsky fossil bed, pressure-treated 4 x 4 inch posts were embedded in concrete at each corner and periodically along the longer sides of the frame. Pressure-treated 2 x12 inch framing lumber was nailed to the posts to complete the frame. Additional 2 x12 inch framing lumber was used to create the dividers. One divider bisects the pit lengthwise down the middle to form two long 6 meter by 2.3 meter sections. The other divider cuts the right-sided section into two shorter sections 3 meters long and 2.3 meters wide. The total cost of lumber and other construction materials was approximately $150.

Since the pit was designed to be an integral part of our school's outdoor learning area, it was located close to an existing 1.2 meter x 5 meter worktable and a shade-covered bench seating area. The semi-circular seating area is used for pre-dig instructions and discussions. The large worktable provides a standing height work surface for students to examine, measure, draw and record observations about their newly discovered fossils (see Photo 2). Students place their clipboards, pencils, magnifying glasses, tape measures and any other post-lab equipment on the worktable before proceeding to the fossil pit for their fossil hunts.

Contents of the Fossil Pit

The first small section of the pit was filled with limestone containing 40 million year old marine fossils from the Eocene Epoch. The limestone was gathered from the Haile Limestone Formation located near Newberry, Florida. Under the guidance of Dr. Roger Portell, an invertebrate paleontologist at the Florida Museum of Natural History, a dump truck was loaded with 7,250 kilograms of limestone from an area that the museum had already investigated and delivered to our newly-constructed pit. Although most of the museum quality fossils have already been removed from this load of limestone, it still contains literally thousands of well-preserved and intact marine fossils, including several different types of mollusk shells, coral skeletons, and other fossilized remains of ancient marine invertebrates. The second small area of the fossil pit was recently filled with 7,250 kilograms of 5-20 million year old fossils from the Miocene Epoch. This area contains fossils from the Bone Valley Formation located along the Peace River in Polk County, Florida and is rich in marine vertebrate fossils, including shark's teeth from several different species, as well as skate and ray grinding plates. The largest of the three areas was filled with terrestrial and marine fossils ranging from 10,000 to 5 millions years old from the Pleistocene and Pliocene Epochs. This 6 meter long x 2.3 meter wide x 0.6 meter deep section was filled with 21,770 kilograms of fossil and substrate from an active museum dig site in Sarasota, Florida (see Photo 3).

During the Pliocene and Pleistocene time periods, many different species of large mammals and reptiles ranged throughout Florida. As a result, this fossil-rich area of our pit contains many prize fossils, such as woolly mammoth leg bones, ground sloth vertebrae, manatee ribs, Archaeohippus and Parahippus horse teeth, ancient deer antlers, giant land tortoise shell fragments, and mastodon tooth and tusk fragments. (See Figure 1 for a diagram of the complete fossil pit.)

The cost of trucking the fossils was not overwhelming considering the many years of use and enjoyment they will bring to our students. The small load for section 1 was hauled locally and only cost $35. The cost of hauling the load for section 2 of the pit was covered by a local day care facility in our town which also recently built its own fossil pit and the large load for section 3 was hauled 150 miles for a cost of $325.

In addition to the fossils already found in the substrate of the largest Pleistocene/Pliocene section of the pit, our local museum donated a wealth of additional fossils. These fossils have been buried in different layers throughout this section of the pit. Students are enthralled when they find huge 8-10 centimeter long shark's teeth that belonged to a long lost cousin of the present day great white shark (Carcharodon carcharis). They also get very excited when they find some of the other buried treasures such as mammoth molars with a mass of one kilogram and 20-centimeter wide mastodon vertebrae. To protect our wealth of fossils from vandalism and "after-hours collecting," a fencing company constructed a two-piece chain link fence cover that we lay on top of the pit and padlock to anchors cemented in the ground. The cover requires two adults to lift and move to the side. Design and construction of the security fence cover cost $650 and we considered it well worth the investment to protect our 20+ year supply of fossils.

Fossil Pit Expeditions

The fossil pit allows us to take our students on a fossil-collecting field trip without ever having to leave our schoolyard. The pit gives students an opportunity to visit a fossil-bearing dig site in a pseudo-field setting. We believe the most important characteristic of the fossil pit is that it allows students to replicate the work of real scientists. They learn science by doing science. Every visit to the pit creates excitement among the students as they anticipate finding a "new" treasure. And since only a fraction of the fossils in the fit have been planted, each visit holds the potential for a new find for the students and teachers. Since all of the substrate comes from active museum dig sites, the possibility exists that the students may make a truly unique discovery of a museum-quality specimen. As Dubowsky and Hartman state, "Is this not the goal of an investigative laboratory?"

Upon consulting with the paleontologists at our local museum, we decided to keep the tools used during the digs as simple as possible. In the real world, paleontologists use old screwdrivers for digging tools and inexpensive paint brushes for cleaning off the dirt. For our school site fossil digs, each pair of students is given two small 1.25-cm wide paintbrushes, two 25-cm wooden skewers, and one 61 cm x 25 cm plastic collection tray. Every student also uses a foam "paleontologist patella pad" (a.k.a. knee pad) from the local dollar store to make the digging experience more comfortable. The students use skewers instead of screwdrivers for digging up the fossils (see Photo 4).

This minimizes the amount of damage and breakage of fragile fossils by enthusiastic diggers. As fossils are found, students use their brushes to gently brush the fossils off and they then set them on their collection trays for later examination (see Photo 5).

Photo -5

Before going on their first dig, students view laser discs and videotapes illustrating real paleontologists working at dig sites. We discuss how these scientists practice methodical digging techniques, good observation skills and patience. Although students keep detailed records of every fossil they find in their field notebooks, they are also allowed to choose one favorite fossil to keep on each visit. The remaining fossils found by students during digs are reburied at the end of each digging expedition after measurements have been taken and drawings have been made.

Addressing Science Process Skills

Currently our fossil pit is used by elementary students from third through fifth grade. Lessons for the fossil pit are evolving as the pit does. During their first visits, our students freely explore in the pit in hopes of discovering a fossil. Many students experience the thrill of discovering a fossil for the first time (see Photo 6). All of our students become junior scientists doing field work as they dig through the layers of dirt trying to distinguish ordinary rocks from fossils. In successive trips, we have found the fossil pit is an excellent place for students to practice applying the basic science process skills of observation, communication, classification, measurement, prediction, inference.

As they learn how to recognize a fossil, they record quantitative and qualitative observations of their fossils in their science field notebooks. With the help of magnifying glasses, students make detailed notes and drawings of their fossils. They also use measuring tapes and balances to measure the size and mass of their fossils. Students also develop a simple classification scheme for their fossils and predict what type of fossil they think will be the one most commonly found in their class. At the end of each dig, students try to infer the origins of their fossils and they use field guides such as A Guide for Identifying Florida Fossil Shells and Other Invertebrates by William Brayfield and Fossil Vertebrates-Beach and Bank Collecting for Amateurs by M.C. Thomas to determine the age and common and scientific names of their fossils.

A Follow-Up Activity

After students have made several expeditions to the pit, we follow up with an activity that simulates the type of work paleontologists do after they return from the field. In this activity developed by Terrie Kielborn (1996), students simulate the reconstruction of a complete fossilized skeleton from its disarticulated parts. Students work in teams of two to uncover a wooden dinosaur or prehistoric mammal model that has been buried in a tray filled with sand. As they uncover the individual skeletal parts they must infer what type of animal they are from and they try to reconstruct the complete skeleton using the parts they find. Again, students use simple tools like wooden skewers and inexpensive paintbrushes. Three different animal models are used throughout the class in order to keep the teams guessing. Once a team thinks their model is finished, they use a picture of the completed model to make comparisons. Students note how close they were to the correct skeletal model.

The Pit's Many Uses and Impacts

We are literally just beginning to scratch the surface of potential uses of our fossil pit. Community interest in our pit is widespread and we have already hosted several short two and three hour field trips for local elementary schools. The Florida Museum of Natural History also uses our pit for its Saturday enrichment programs and summer camp programs for elementary students. Our pit has also been used for inservice teacher workshops and pre-service teacher methods courses. Next year we hope to expand use of the pit into the middle school grades with more intricate excavations and gridding activities.

One indication of the fossil pit's success is student testimonials. Last year, when the fourth grade classes were asked to write about their favorite science activities from the entire year, 30% of the students said digging in the fossil pit and excavating/reconstructing the wooden skeleton models were their two favorite science activities. Many of the responses were similar to these: Tiffany - "My favorite time in Lab was when we went to dig for fossils. The reason I liked it was because we got to dig for them and we got to keep one and it was very fun and I liked it a lot." Kendra - "My favorite lab in 4th grade was the fossil dig. I liked when I found the big bone. It was cool and I wish that we could do that again." Shanica - "My favorite part of lab was when we put the dinosaurs together because I felt like a real scientist."

Acknowledgments

The authors are indebted to Dr. Russ McCarty, Dr. Roger Portell, and Dr. Bruce MacFadden of the Florida Museum of Natural History at the University of Florida in Gainesville for their support, guidance and contributions to this project. And to the Florida Game and Fresh Water Fish Commission, the Bingham Environmental Education Foundation, and Safari Club International for providing financial grant support for this project.

References

Brayfield, W and L. (1993). A Guide for Identifying Florida Fossil Shells and Other Invertebrates, Third Ed. Gainesville, FL: Florida Paleontological Society, Inc., Florida Museum of Natural History.

Brown, Robin C. (1988). Florida's Fossils - Guide to Location, Identification and Enjoyment, Sarasota, FL: Pineapple Press.

Hartman, E.M. Jr. and N. Dubowsky. (1989). The transported fossil bed. The American Biology Teacher, 51(7): 424-425.

Kielborn, T. (1996). A blast from the Jurassic past. The Florida Science Teacher, 11(3): 6-11.

Thomas, M.C. (1995). Fossil Vertebrates - Beach and Bank Collecting for Amateurs, Gainesville, FL: Florida Paleontological Society, Inc., Florida Museum of Natural History.

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