ASBOG Practice Exam

What type of fold is characterized by limbs that close upward to the fold axis?

1. Synform

2. Syncline

3. Antiformal

4. Anticline

The correct answer is: Anticline

The correct answer is related to the structural geology of folds. An anticline is characterized by a geological fold that arches upward, with the limbs of the fold bending away from the central axis. This upward closure of the limbs creates a convex shape, resembling an arch. The rocks at the core of an anticline are typically older than those on the limbs, due to the process of folding where younger layers are pushed up and over older layers. In contrast, a syncline is a type of fold where the limbs dip toward the fold axis, resulting in a concave shape. Synforms and antiformal terms are less commonly used yet can be related to specific scenarios or contexts; usually, the terms anticline and syncline are the primary focus when discussing folds in structural geology. Understanding the terms and characteristics of folds helps in interpreting geological structures and their formation processes in the Earth’s crust.