Folding and Faulting

What is a Fold? A fold is a bent rock

layer or series of layers that were originally horizontal and subsequently deformed.

Due to compression forces.

They are most visible in rocks that have layers.

Types of Folds The two most

common types of folds are, anticlines and synclines.

Anticlines are the up-folding and/or arching of sedimentary layers.

Synclines down-folds or troughs.

Types of Folds The simplest type of

fold is called a monocline.

This fold involves a slight bend in otherwise parallel layers of rock.

There is a single slope

What is a Fault? Faults are a break in

a rock mass along which movement has occurred.

When the stresses overcome the internal strength of the rock, resulting in a fracture.

Types of Faults: Normal Faults Fault in which the

rock above the fault plane has moved down relative to the rock below.

Formed by tension.

Footwall

Types of Faults: Reverse Faults Fault in which the

material above the fault plane moves up in relation to the material below.

Formed by compression

Hanging wall

Graben A valley formed by the downward

displacement of a fault-bounded block. Produced when tensional stresses result in

the subsidence of a block of rock.

Horst An elongated, uplifted block of crust

bounded by faults. Development of two reverse faults causing a

block of rock to be pushed up.

Types of Faults: Transform Fault

A major strike-slip fault that cuts through the lithosphere and accommodates motion between two plates.

These faults are vertical in nature and are produced where the stresses are exerted parallel to each other (shear).

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