Stratigraphy
Stratigraphy is the study of rock layers and what they reveal about Earth's history.
Think of it this way
A kitchen tray holds layers of food stacked one on top of the next. The bottom layer went down first, and the top layer went down last. Each layer tells you what was served and in what order. Reading the layers from bottom to top shows the full meal history of the tray.
Explaining stratigraphy by grade level
Rocks form in layers, one on top of another. The bottom layers are the oldest. The top layers are the newest. You can see these layers in cliffs and canyon walls. Each layer tells a story about what happened long ago. Some layers have fossils inside them.