folding

In geography, folding is a crustal deformation process alongside faulting. It is common for the surface of the earth to deform. This deformation comes as a result of forces strong enough to move sediments of the ocean to an elevation of many meters above the sea level. This displacement of rocks can be as a result of intrusive igneous activity, volcanic activity, tectonic plate movement, and subduction. Let’s dig in and find out more.

LEARNING OBJECTIVES

By the end of this topic, you are expected to;

• Understand the meaning of folding and faulting
• Know the major causes of folding
• Know the different types of folds

Rock deformation involves changes in the volume and/or shape of these substances. Changes in volume and shape occur when strain and stress causes a rock to buckle and fracture or crumble into folds. Folds can be simply defined as bends in rocks as a response to compressional forces. Folds are more visible in rocks containing layering. The following are some of the conditions that must be met for plastic deformation of rock to occur:

• Deformation must be applied slowly
• Pressure must not exceed the internal strength of the rock. If it does, fracturing will occur.
• The rock material must have the ability to deform under heat and pressure.
• The higher the rock temperature, the more plastic it becomes.

Different folds have been recognized by geologists and classified. The simplest fold type is called a monocline. This fold involves a slight bend in otherwise parallel layers of rock.

An anticline fold is a convex up fold in rock resembling an arch-like structure with the limbs (or rock beds) dipping away from the center of the structure.

A syncline refers to a fold where the rock layers are wrapped downward. Both synclines and anticlines are as a result of compressional stress.

More complex types of folds can develop in situations where lateral pressures become greater. The greater pressure causes synclines and anticlines that are asymmetrical and inclined.

A recumbent fold develops in the center of the fold moves from being once vertical to a horizontal position. Recumbent folds are mainly found in the core of mountain ranges and indicate that compression and/or shear forces were stronger in one direction. Extreme pressure and stress can sometimes result to rock shearing along a plane of weakness creating a fault. An overthrust fault is a name given to the combination of a fold and a fault.