Syncline at Split Rock, Cheverie, Nova Scotia

What are geologic structures?

Geologic structures in the most general sense include all parts of the Earth's crust where the properties of the rocks either:

• vary from place to place (i.e. they are heterogeneous); or
• vary with direction (i.e. they are anisotropic).

That includes a lot! Structures can be conveniently classified as either:

• primary - formed at about the same time as their host rock, or
• secondary - imposed on older rocks as a result of deformation.

'Structural geology' is generally understood to be the study of structures in this second category, though structural geologists need a good understanding of primary structures too.