Final answer:
Folds are a type of brittle deformation that can be identified in the field based on their shape and the placement of rocks.
Step-by-step explanation:
Folds are a type of brittle deformation that occurs when the Earth's crust is shortened during plate tectonic convergence. They are important geologic structures that can accumulate resources such as petroleum or gold. Folds can be identified in the field based on their shape and the placement of the oldest and youngest rocks.
They result from the plastic deformation of rocks in response to tectonic forces, and they are commonly associated with compressional stress. Folds are a characteristic feature of ductile deformation, where rocks bend and warp without breaking. In contrast, brittle deformation involves the fracturing and breaking of rocks, leading to features such as faults and fractures.