How is an asymmetrical fold characterized?

An asymmetrical fold is characterized by having one limb that dips more steeply than the other. This means that the angle at which each limb of the fold tilts towards the horizontal differs. In geological terms, this signifies that the forces acting on the rock layers during the folding process were not evenly distributed, creating an uneven profile. Such folds are typically a result of differential stress, where one side of the fold experiences greater pressure than the other, leading to varying angles in the two limbs.

The other answer options describe different types of folds or folding characteristics. For instance, having both limbs dipping at the same angle indicates a symmetrical fold, which is distinctly different from an asymmetrical fold. Horizontal limbs do not apply to the definition of an asymmetrical fold either, as folds commonly involve tilted or inclined layers. Lastly, one limb being completely upside down describes an overturned fold, which is a specific variation that results when folding is extreme and is not a defining characteristic of asymmetrical folds in general.