What term describes a rock deformation pattern that forms ridges and valleys due to horizontal compression?

• A. Faults
• B. Plateaus
• C. Folds
• D. Valleys

Answer: (C)

Rocks deform by compressive forces causing the layered rocks to buckle and bend rather than break. When horizontal compression acts on sedimentary layers, they can fold into arches and troughs. The crests become ridges (folds that arch upward) and the troughs become valleys (folds that dip downward). This bending happens more readily when rocks are warm and ductile, often at depth in the crust, and it’s a key process in mountain-building. This pattern is different from faults, where rocks fracture and slide along cracks, creating displacement rather than a continuous bend. Plateaus are high, flat-topped regions formed by uplift, not by folding. So the term describing this deformation pattern is folding.