DEFORMATION OF ROCKS BH 
of the layers. A strong stratum may deform weaker layers, 
geologically below, into the fan form by producing flowage in 
them. The formation of the fan fold may be further assisted 
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Fic. 6.—a, Diagram of fold in limestone of the Jura Mountains, showing hinge-like 
bending at sides of anticlines: 4, the same somewhat more closely compressed, so that 
the fold has become fan-shaped. 
by the tendency of rocks to bend farther at a place where 
deformed rather than to bend in a new place. The different 
phases of the formation of fan folds are illustrated in the Jura. 
In the folds of certain parts of the Jura one is impressed with 
the flatness of the anticlinal domes and the synclinal troughs, the 
steepness of the limbs, and the rapidity of the change from flat 
dips at the anticlines and synclines to nearly vertical dips on the 
