Why do rim synclines form around growing salt domes?

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salt dome Figure 1: Interrelationships of salt structures (see text)

Rim synclines form around growing salt domes as a direct consequence of the movement of salt from surrounding areas into the dome structure.

As salt begins to flow from an undeformed bed toward a central point to form a salt pillow, it creates a localized uplift of the overlying strata. Because the salt is being evacuated from the immediate vicinity to feed this growth, the area from which the salt originated loses volume and consequently subsides. This subsidence creates a circular depression known as a rim syncline that encircles or nearly encircles the developing dome.12