7.1 Fluid-driven fractures in nature

Magmatic dikes form when pressurized magma overcomes the minimum principal stress in the subsurface. Dikes form large vertical planes in places with marked stress anisotropy with $S_3 = S_{hmin}$. Search in the web “Shiprock New Mexico” to find more great pictures of dikes.

Figure 7.1: Formation of dikes and examples. Dikes are large and natural fluid-driven fractures.