In structural geology, an anticline is a fold that is convex up and has its oldest beds at its core. The term is not to be confused withantiform, which is a purely descriptive term for any fold that is convex up. Therefore if age relationships between various strata are unknown, the term antiform must be used.
On a geologic map, anticlines are usually recognized by a sequence of rock layers that are progressively older toward the center of the fold because the uplifted core of the fold is preferentially eroded to a deeper stratigraphic level relative to the topographically lower flanks. The strata dip away from the center, or crest, of the fold.
If an anticline plunges (i.e., is inclined to the Earth's surface), the surface strata will form Vs that point in the direction of plunge. Anticlines are typically flanked by synclines although faulting can complicate and obscure the relationship between the two. Folds typically form during crustal deformation as the result of compression that accompanies orogenic mountain building.