A Backyard with a Hidden Past
Behind Nia's backyard bench, a rock ledge sticks out of the ground. Nia notices shapes in the rock. An adult fossil scientist visits and helps her study them. They take photographs without breaking or digging into the ledge. Fossils are remains or traces of living things from long ago. A shell, a leaf print, or a trail of footprints can become a fossil.
The scientist shows Nia a guide. Sea clams have two hard shell halves. Their living relatives live in salty ocean water. Corals are animals, and the living relatives of these fossil corals also live in ocean water. The guide's pond snails have coiled shells and live in fresh water. Its pond plants grow in fresh water. Ferns have leaves with patterns of veins. Their leaves can sometimes wash into nearby water.
Nia makes a notebook record:
Lower layer A: Fossils match the guide's sea clam shells and corals. No fish fossils were found.
Upper layer B: Fossils match the guide's pond snail shells, pond plants, and fern leaves. A row of small fossil footprints also crosses the rock.
The scientist explains that layer A formed before layer B. The layers formed long before the backyard existed. The footprints show separate steps, but they do not have enough detail to identify the animal. The notebook does not record the organisms' original colors or the exact ages of the fossils.