Panum Crater shear cracks

3D Model

The en-echelon open fractures in this outcrop were created during extrusion of a hot and pliable mass of obsidian. The surface of the obsidian was moulded against a cooler rock face, forming the long grooves that structure this outcrop. Drag forces along the outside of the cooling obsidian mass caused the formation of the many gashes that give the outcrop its stretch-mark appearance.