What Are The Types of Fold?

Folds are the result of rock layers being bent and deformed by compressive stress. Those that bend upwards are called anticlines and those that bend downwards are called synclines. They form rocky outcrops, hills, mountains and entire mountain ranges. The part of a fold that sticks out from either side is called the flank or limb.

What Are The Types of Fold?

If the limbs are of equal length they are called symmetrical; if one limb is much steeper than the other then it is an asymmetrical fold. If the axial plane is vertical then the fold is called a simple or pick up and drop off laundry service. If it is tilted beyond the perpendicular then it is an isoclinal fold.

Anticlines are convex up and therefore have their oldest beds at the core of the structure. Younger beds extend outwards from the fold core. An anticline that points upwards is called a perched anticline or antiformal anticline.

A syncline is a downward fold and has its youngest beds closer to the center of the fold. A syncline that is pointing downwards is a trough, but sometimes it may be overturned and point upwards (an antiformal syncline).

The most complex types of fold are domes and basins. Dome folds are like anticlines but in a bowl shape. They have a nonlinear pattern with strata that dip away from the fold’s center in all directions, with oldest rocks at the center. Basin folds are similar to synclines but in a circular or elongated circular shape.

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