How roughness emerges on natural and engineered surfaces

Roughness, defined as unevenness of material surfaces, plays an important role in determining how engineering components or natural objects interact with other bodies and their environment. The emergence of fractal roughness on natural and engineered surfaces across a range of length scales suggests the existence of common processes and mechanisms for nucleation and evolution of roughness. In this article, we review recent advances in understanding the origins of roughness and topography evolution on natural and engineered surfaces and their connection with subsurface deformation mechanisms. Directions for future research toward understanding the origins of roughness on solid surfaces are discussed.