The horizontal fractures depicted in the Photographs below can be interpreted as sheeting joints because they are parallel to the ground surface, shallow, persistent, and closely spaced. A possible mechanism for their formation is axial splitting under a horizontal compressive σ₁ and a vertical σ₃ (Section 3.6).

In this case the rock is a massive granite and the sheeting joints are connected through relatively sparse vertical fractures (left side of the larger Photograph). The weathering (brown color) accompanying the sheeting joints may indicate a present day or recent existence of flow along them. Would you expect this flow to be present at depths greater than, say, 100 m?

Photograph from Québec City-Saguenay highway, Canada, by Alain Rouleau

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