Where does weathering collide?

In geology, weathering is the breakdown and chemical alteration of rock and mineral where they sit at or near the Earth's surface, driven by physical agents such as freezing water and temperature change and by chemical agents such as water, oxygen, and dissolved acids. Merrill's 1897 A Treatise on Rocks, Rock-Weathering and Soils gave the process its systematic geological treatment, describing how solid rock is loosened and decomposed in place before any loosened material is carried off. The referent is destruction that happens where the rock lies, with no transport, which sets it apart from the accelerated health decline of a stressed population and from the outdoor degradation of a manufactured material.[1]

Unit

A rock or mineral surface altered in place, by depth and degree of alteration

Recovery means

Not applicable

Measured by

Assessed by weathering rind thickness, mineral loss, chemical depletion indices, and change in rock strength

In public health, weathering is the hypothesis that repeated exposure to social and economic adversity accelerates biological decline, so the health of a disadvantaged group deteriorates earlier in life than it otherwise would. Geronimus coined the word in her 1992 paper The weathering hypothesis and the health of African-American women and infants in Ethnicity & Disease, proposing that cumulative stress leaves a measurable physiological mark; her 2006 study with colleagues later operationalised it by comparing allostatic load scores across groups and ages. The referent is a pattern of population health tracked across the life course, and it has nothing in common with rock breaking down in place or a manufactured material degrading outdoors beyond the shared word.[2][3]

Unit

A group's health trajectory across age, relative to a comparison group

Recovery means

Not applicable

Measured by

Operationalised through biomarkers of cumulative physiological stress, notably allostatic load scores, compared by group and age

In materials science and engineering, weathering is the degradation of a manufactured material exposed to the outdoor environment, as sunlight, oxygen, heat, moisture, and pollutants act on polymers, coatings, and other products over their service life. White and Turnbull's 1994 review Weathering of polymers in the Journal of Materials Science set out the degradation mechanisms, the stabilisation strategies, and the natural and accelerated testing used to predict how long a material lasts. The referent is the loss of properties in an engineered material, followed in the laboratory and the field, and it stays distinct from the in-place breakdown of natural rock and from the accelerated health decline of a stressed population.[4]

Unit

A material specimen's property loss under environmental exposure over time

Recovery means

Not applicable

Measured by

Tracked by changes in gloss, colour, mechanical strength, and mass under natural or accelerated weathering exposure