Rock Records at Juniper Bluff Camp

A Bluff Beside the Tents

On a camping trip to Juniper Bluff, a youth hiking club visits a marked viewing area beside a rock face. The tents stand on dry ground above the bluff. No lake or sea covers the campsite today. From the viewing area, the campers can see four rock layers stacked one above another. They study the layers without climbing or removing fossils.

A field scientist explains that sand, mud, and other sediments can pile up and later become rock. Remains of living things can sometimes be preserved as fossils. At this bluff, the layers have stayed in their original order. A lower layer formed before the layer directly above it. The campers label the layers A through D, starting at the top.

Field record: top to bottom
A — Tan rock with fossils of sea clams and sea snails.
B — Gray rock with fossils of lake snails and tiny freshwater fish.
C — Brown rock with several fossil tree stumps. Their roots reach into preserved soil beneath the stumps.
D — Dark rock with fossils of sea clams and sea snails.

Scientists identified the fossil kinds in the record. The sea clams and sea snails were animals that lived in shallow salt water. The lake snails and fish were kinds that lived in freshwater lakes. The rooted stumps were trees that grew on land. Scientists also checked that these fossils were preserved where the organisms lived, rather than washed in from another habitat.

The campers sketch the stack and record which fossils occur together. They keep each fossil observation connected to its layer letter. Their notes do not include the ages of the layers in years or how long each layer took to form. Back at camp, the group uses its record to investigate the bluff's history.