Answer:
A geological event shifted the rocks
Step-by-step explanation:
The rock layers have the natural tendency to layer up in horizontal manner, thus to be positioned one above the other. This actually means that the rock layers are sorted out by age, with the ones on the bottom being the oldest ones, and the ones on top the youngest ones. The Earth is not static though, and there's constant movements, geological activities, that disturb the rock layers. If there are geological activities that will push up and than move sideways the rock layers, the rock layers will appear to have vertical layers, not horizontal ones, thus giving a nice clue about how they came to be in that position.