Tectonic Folding

Diagram of folding
Diagram of different types of folds. Think of a stack of blankets on a table top that you push together so that they wrinkle up. Now imagine what would happen if you sliced the peaks of the folds so that the height was the same.

R.J. Lillie. 2005. Parks and Plates.

Folding- Folding occurs when tectonic processes put stress on a rock, and the rock bends, instead of breaking. This can create a variety of landforms as the surfaces of the folded rocks are eroded.

Anticlines are folds shaped like an arch, and synclines are shaped like the letter 'U.' 

Geologists recognize these formations by what is visible at the surface. Look at the diagram of the syncline and notice how the surface shows a symmetrical pattern with the youngest rock in the middle and older rocks appearing on either side. Notice that the opposite is true of the anticline.