Geometry Of A Fold: An upward fold is called an anticline, while a downward fold is called a syncline. In many areas it’s common to find a series of anticlines and synclines , although some sequences of rocks are folded into a single anticline or syncline. A plane drawn through the crest of a fold in a series of beds is called the axial plane of the fold. The sloping beds on either side of an axial plane are limbs.
- When describing a fold in the Earth’s crust, we say it’s symmetrical if the angles between each limb and the axial plane are generally similar. On the other hand, it’s asymmetrical if these angles differ.
- If the axial plane is tilted enough that one side’s beds are tilted past vertical, we call the fold an overturned anticline or syncline.
- An isoclinal fold is a very tight fold where the limbs are parallel or nearly parallel to each other.
- When isoclinal folds are overturned to the extent that their limbs are almost horizontal, we refer to them as recumbent folds.
- Folds come in various sizes, and it’s common to find smaller folds within larger ones. Large folds can have wavelengths of tens of kilometers, while very small ones might only be visible under a microscope.
- Anticlines don’t necessarily appear as ridges, and synclines aren’t always seen as valleys in the terrain.
- Folded rocks undergo erosion like any other rocks, and the resulting topography is mainly influenced by the varying resistance of different layers to erosion.
Read Also: What Is A Fold?
