Answer:Syncline
Explanation:A syncline is a fold in which the youngest rocks occur in the core of a fold (i.e., closest to the fold axis), whereas the oldest rocks occur in the core of an anticline.
A fold of rock layers that slope upward on both sides of a common low point. Synclines form when rocks are compressed by plate-tectonic forces. They can be as small as the side of a cliff or as large as an entire valley.
Synclines are formed when tectonic plates move toward each other, compressing the crust and forcing it upward.
