Forms of Folding Rocks
- Anticline:
- An anticline is a rock bed that is upfolded into an arch from a few feet to many miles across. If it contains many lesser folds, it is an anticlinorium. A huge anticline is a geanticline.
- Monocline:
- A monocline is a steep step-like fold, bounded by upper and lower bends in a set of rock layers.
- Nappe:
- A nappe is a recumbent fold sheared through so that the upper side is forced forward a number of miles. A nappe with rocks forced over each other is an imbricate structure.
- Overfold:
- An overfold is a lopsided anticline with one side forced over the other.
- Pericline:
- A pericline is an anticline in the form of an elongated dome.
- Syncline:
- A syncline is downfolded sedimentary rock layers that form a basin. If it has subsidiary synclines, it is a synclinorium. An immense syncline is a geosyncline.
Faults
- Graben:
- A graben is a long, narrow block sunk between two parallel faults.
- Horst:
- A horst is a horizontal block raised between two normal faults.
- Normal fault:
- A normal fault occurs when stretching breaks rocks along a steep fault plane and one block drops or rises against the other.
- Reverse fault:
- A reverse fault occurs when compression forces one block up and over another. A thrust fault is a reverse fault with a low-angled fault plane producing great horizontal movement.
- Tear fault:
- A tear fault is a horizontal shearing along a vertical fault plane. A transfer fault is a tear fault at right angle to an oceanic ridge.
- Tilt block:
- A tilt block is an uplifted, tilted block.
