Final answer:
Anticlines, which are geologic folds resulting from horizontal compression that shortens the crust, are characterized by a convex shape with the oldest rocks in the core. They form from compressional stress during plate convergence and are important for trapping natural resources.
Step-by-step explanation:
The formation that results from horizontal compression and results in a shortening of the crust involved is known as an anticline. Anticlines are geologic folds characterized by a convex shape, with the oldest rocks at their core and younger rocks toward the outside. This contrasts with a syncline, which features the youngest rocks at the center and the oldest on the outside, often exhibiting a concave shape.
Anticlines are the result of compressional stress associated with plate tectonic convergence, where the crust is pushed together and forced to buckle upwards. This upward bending of rock layers can form mountain ranges or ridges and can be significant in the trapping of resources like petroleum. In contrast, synclines dip downwards and can also occur in the same settings as anticlines, forming in parallel.