microweathering

Microweathering is a term used in geology and geomorphology to describe weathering processes that operate at microscopic to near-microscopic scales within rocks and minerals, driven by local microclimatic conditions at grain contacts, pore spaces, and mineral interfaces. It emphasizes heterogeneity: microenvironments can experience moisture, temperature, and chemical gradients that differ from the surrounding rock, producing distinct weathering patterns.

Mechanisms include chemical weathering such as hydrolysis, dissolution, and oxidation that propagate along grain boundaries and within micro-pores, and physical weathering such as microcracking from thermal expansion/contraction and salt crystallization in confined pores. Biodeterioration by microbes can enhance weathering locally through acids and biofilms. These processes can act simultaneously, with transport of fluids and ions at the pore scale sustaining reactions.

Scale and impact: Microweathering produces micro-pits, etching, and surface roughening, contributing to overall rock weakening and increased porosity. It can create heterogeneous degradation patterns that influence durability of rocks and stone surfaces, regolith formation, and soil genesis, especially in highly porous or carbonate materials.

Evidence and methods: Studies rely on high-resolution imaging (scanning electron microscopy and micro-CT), nanoscale spectroscopy, and controlled micro-environment experiments that simulate microclimates. Numerical models of pore-scale transport and reaction help connect micro-scale processes to macro-scale weathering rates.

Terminology and status: The concept is used variably and sometimes overlaps with microscale weathering or micro-weathering. It remains an area of active research, with ongoing debates about definitions and the relative importance of microweathering compared with larger-scale processes.