Solve a Sedimentary Layers Puzzle

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Did you know that the history of life on Earth is told through rocks? Over millions of years, sediments such as sand and silt were laid down and compressed to form sedimentary rock layers. They preserve a record of ancient landscapes, climates, and organisms.

Scientists often determine the correct sequence of sedimentary rock layers using the fossils found within them. They compare the fossils to fi gure out if two layers are from the same geologic time period, or if one layer is older than the other.

1. Photocopy and cut out the five strips of paper Each strip represents a sedimentary rock layer formed during a certain time period.

2. Put the layers in correct order Begin by placing B, the “oldest layer,” on the bottom. Then decide which layer comes next. It will have some of the same organisms as the older layer and some new ones. (Hint: Organisms do not disappear for a layer and then reappear.) Place it above. Continue until the layers are in order, with the youngest at the top. Check your answers and write the time period on each layer.

Look at the fossils within each layer. What plants and animals lived during the same time period? Then compare the layers to explore the changing plant and animal groups throughout Earth’s history. Which organisms survived from one time period to the next? Which ones went extinct? Could Tarbosaurus have hunted Seismosaurus? What organisms survived the mass extinction at the end of the Cretaceous Period?