Final answer:
An anticline is a fold where the oldest rocks are in the center and the youngest rocks are on the outside, while a syncline is the opposite. An asymmetric anticline has uneven limbs, a recumbent fold has a horizontal axial plane, and a monocline has only one bend in the rock layers.
Step-by-step explanation:
An anticline is a fold in the Earth's crust where the oldest rocks are in the center and the youngest rocks are on the outside. It often appears as a convex-upward fold or a dome-shaped structure. On the other hand, a syncline is a fold where the youngest rocks are in the center and the oldest rocks are on the outside, resembling a concave-upward fold or a smile-shaped structure.
An asymmetric anticline is an anticline with limbs of uneven length, while a recumbent fold is a fold where the axial plane is horizontal. Finally, a monocline is a fold with only one bend in the rock layers.