Which structural failure mode most threatens ziggurats constructed with unbaked mud bricks subjected to seasonal rainfall?

💡 Explanation

When unbaked mud bricks are exposed to seasonal rainfall, efflorescence can occur because soluble salts migrate to the brick surface and crystallize upon evaporation, causing the surface to flake and decompose. Therefore, decomposition via efflorescence is most likely, rather than shear failure, insect damage, or thermal fracture which depend on different environmental factors.

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