Get premium membership and access revision papers with marking schemes, video lessons and live classes.
Processing. Please wait.

 Form 2 Geography Online Lessons on Internal Land Forming Processes

Lesson on folding, types of folds and the resultant features of folding

 (9m 8s)
1014 Views     SHARE

Download as pdf file

Answer Text:
-Process in which crustal rocks are distorted by compressional forces by being caused to bend upwards and downwards. It occurs on fairly young sedimentary rocks.
Parts of a Fold
(a) Anticlines (upfolds)-parts of the earth’s surface which bend upwards when folding occurs.
(b) Synclines (down folds)-Parts of the earth’s surface which bend downwards when folding occurs.
(c) Crest-upper most part of Anticline.
(d) Trough-lowest part of a syncline
(e) Limp-rock layers sloping on both sides of a fold
(f) Axis-imaginary line drawn vertically through the centre of the anticline.
Types of Folds
1. Simple Symmetrical Folds
- Which are symmetrical about the anticline.
- Formed by 2 compressional forces of equal magnitude.
2. Asymmetrical Folds
- Which are asymmetrical about the anticlines axis or in which one limp is steeper than the other.
- Formed by two compressional forces of unequal magnitude in which one is stronger than the other.
3. Over Folds
- In which anticline of one fold is pushed over the limp of the other.
4. Isoclinal Folds
- Which are packed closely together and with limps almost parallel to each other.
- Vertical Isoclinal folds are formed by compressional forces of equal magnitude while inclined Isoclinal folds are formed by forces of unequal magnitude.
5. Recumbent Folds
- Which lie in a horizontal manner.
- Formed by two compressional forces one of which is very strong.
6. Nappe/Overthrust Fold
- In which one limp is pushed over the other limp.
- The forces are very strong and they cause a fracture/fault to develop.
7. Anticlinorium and Synclinorium Complex
- Folds characterized by minor upfolds and minor downfolds.
• Land is first subjected to weak compressional forces resulting into minor folds.
• Later the land is subjected to much greater compressional forces resulting into new upfolds with minor folds (Anticlinorium) and new down folds with minor folds (Synclinorium).