Universal fluctuation of polygonal crack geometry in solidified lava

Outcrops of columnar joints made solidified lava flows are often covered by semiordered polygonal cracks. The polygon diameters fairly uniform at each outcrop, but their shapes largely vary in the number sides and internal angles. Herein, we unveil that statistical variation shape follows an extreme value distribution class: Gumbel distribution. law was found to hold for different joints, regardless locality, lithologic composition, typical diameter. A common implies a universal class may integrate crack networks observed on surface various fractured brittle materials.