Finding and Dating
Peggy helps unearth a Diplodocus dinosaur skeleton, David finds out how the bones are dated.
Paleontology is the science of discovering and analyzing excavations and by amateur fossil-hunters, who stumble onto something curious. Skulls and teeth are more frequently found than other parts because of their solid and hard characteristics. Sometimes softer parts, such as ribs, bones or skin can be found if they have been protected from rapid decay and mineralization.
To excavate a fossil, scientists establish coordinates over an excavation site. Using a variety of techniques from dynamiting and digging, covering the entire area in a plaster cast for transport to laboratories and cleaning with small picks and brushes, they preserve the dinosaur's fossils.
Dating the fossils is an important aspect of the scientist's work. There are three ways paleontologists determine the age of a fossil. One is studying how deeply the fossil was buried. Another is using chronometric techniques (chrono=time, metric=measurement) which include Carbon-14 and Potassium-Argon dating. The third dating method looks at the Earth's magnetic field and its patterns in history. When these fields are preserved in rock, they leave a pattern that is unique for each span of geologic time.
Element--A substance made of identical atoms, which cannot be made into simpler units by a chemical process, but can spontaneously change through radioactive processes.
Excavation--To remove soil by digging.
Fossil--The evidence of the past existence of an organism. Fossilization can occur as actual remains; petrifications, where the original organic matter is replaced by minerals like quartz, calcite and pyrite; molds or casts of organisms; carbonized traces of plants found in rock or tracks, trails and burrows.
Diplodocus--A giant herbivorous dinosaur which lived 213 to 144 million years ago.
Sedimentary Rock--Formed of fragments transported over time from their source and deposited by water.
Investigate ways paleontologists discover and analyze fossils to decipher the history of life on Earth.
You and your fellow students will work cooperatively as "paleontologists" to investigate and excavate "fossil" bones in a miniature classroom dig site. Prepare several boxes as dig sites (approximately five students per box) by compacting successive layers of soil and placing bones within soil layers. Exchange dig site boxes so each group is working on a different box than they prepared.
1. Prepare the boxes for the dig sites.
2. Attach string over the top of the box containing your group's dig site at six inch intervals with thumb tacks to represent your coordinates. Letter or number string locations (see Figure A).
3. Dig and brush carefully to locate and remove any "fossils." Record the locations of where you found the bones on a paper diagram that has the same coordinates as your box. You also should record the depth of the find.
1. How is the classroom dig similar to and different from a scientific dig?
2. Why are coordinates important to a dig site?
3. Why do you think fossils are more often found in sedimentary rock formations?
Imagine that you are in a time machine and can visit the time dinosaurs lived. Write a story that describes what you see, hear, feel and do. You may also want to illustrate your work.
Investigate sedimentation. Shake water, soil, small pebbles and rocks inside of a closed jar that you can see through. Allow the jar to stand for a day, then observe the layers that form. What is the bottom layer? What is the top layer? Why is there a difference between the two layers?
Imagine that you are a reporter writing an article at a fossil dig site. Describe what the paleontologist would do first, second, third, etc., at the excavation site and the procedure that the scientist might follow when the fossils are assembled at the laboratory.
Draw different dinosaurs and identify their approximate size and weight. List the dinosaurs on a chart and compare physical characteristics like feet, mouths or heads.
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Educational materials developed with the National Science Teachers Association.