Anticline and Syncline

Abstract

Descriptions of anticlines and synclines in high school Earth Science textbooks are often inaccurate. Most current textbooks define anticlines as convex-upward folds and synclines as convex-downward folds. However, a convex-upward fold is not necessarily an anticline, nor is a convex-downward fold necessarily a syncline. The key to correctly identifying anticlines and synclines in folded strata lies in understanding the stratigraphic facing (or “up”) directions in both limbs of a fold. High school textbooks should incorporate schematic diagrams of folds that clearly indicate the facing directions. Anticlines should be defined as folds in which stratigraphic up directions in both limbs diverge, while synclines are folds in which they converge.