Weathering Rates of Stone-built Heritages

Abstract

It is difficult to estimate weathering rates of rocks based on actual landforms. However, using stone-built architectures, artifacts, and traces of human activity on rock surfaces, weathering rates of rocks under weathering-limited conditions can be obtained easily because stone-built heritages, in general, have a geometrical shape and zero-datum levels. In addition, it is possible to estimate weathering rates of a millennium-scale and changes of rates up to a millennium scale. Many studies on weathering rates of rocks use stone-built heritages. This study reviews recent geomorphological studies that estimate weathering rates, and summarizes their trends. Most of the studies analyze gravestones and churches built since the 19 th and 11 th centuries, respectively. Such stone-built heritages are more commonly located in humid temperate areas. Weathering rates are estimated mainly from surface recession or surface loss of gravestones and church-building stones. The major three building stones─carbonate rocks (rate: 2⊖90 mm/ka) , sandstone (8⊖100 mm/ka) , and granite (5⊖65 mm/ka) ─have different ranges of weathering rates. Among these stones, the rates for carbonate rocks are sensitive to climatic conditions and atmospheric sulfur dioxide concentrations. The results of the studies reveal that weathering rates show an obvious dependence on aspects. North-facing surfaces tend to have lower rates than surfaces facing other cardinal directions because each surface has different temperature and moisture conditions due to insolation. Moreover, the studies reveal that temporal changes in weathering rates rarely fit a simple linear model. Changes in atmospheric acidity, landform development, and vegetation cover rapidly affect the intensity of weathering processes and cause fluctuations in weathering rates.Key words： stone-built cultural heritage, building stones, stone decay, physical environmental stress ：石造文化遺産，石材，石材劣化，自然環境ストレス ＊ 日本大学文理学部

Influence of microclimate on the directional dependence of sandstone pillar weathering in Angkor Wat temple, Cambodia

“…These weathering processes are thought to be restricted by direction dependent (Waragai 2005b;Waragai et al 2006;André et al 2012;Hiki 2012;Hiki and Waragai 2014;Waragai 2016), especially for the temples at Angkor. Regarding cultural stone weathering, previous studies have shown the importance of direction or aspect related to heating-cooling repetitions and moisture changes (Meierding 1993;Paradise 1995Paradise , 2002Williams and Robinson 2000;Waragai 2017). Recently, a relationship between the weathering of sandstone pillars and the pillar water content in conjunction with the microclimatic conditions has been pointed out (Hiki and Waragai 2014).…”