Exergy as a Sustainability Measure in the Ancient Sandstone Art World

By Kaufui Vincent Wong, University of Miami

Visiting the canyon lands of Southern Utah is not only good for the mind and body, but it is nourishment for the soul too. The ring of canyon national parks (which count the renown Grand Canyon) include the Zion National Park, the Bryce Canyon National Park and Arches National Park. The buff-color Navajo sandstone and the vermilion-color Entrada sandstone have been carved by wind and water and the sun into various inspirational sculptures and works of architecture and art. In this document are some photographs by the author of some inspirational sculptural and architectural examples from these parks in the U.S.A.

Fig. 1. Grottoes, Bryce Point, Bryce Nat.Park Fig. 2. Delicate Arch, Arches Nat. Park

Included here are also photographs obtained from the Internet of famous grottoes in China, which are the subjects of discussion in the current document. Figure 4 is that of ceiling paintings in the Yungang Grottoes, a United Nations Educational, Scientific and Cultural Organization (UNESCO) World Heritage Site. (Figure 4 is from Wikipedia.) These are ancient Buddhist temple grottoes near the city of in the Chinese province of . They are very good examples of rock-cut architecture and one of the three most famous ancient sculptural sites of China. The other two are Longmen, Fig. 5, and Mogao, Fig. 6.

Fig. 3. Temple Sinawava, Zion Nat. Park. Fig. 4. Ceiling Paintings, Yungang Grottoes.

Fig. 5. , China. Fig. 6. Mogao Grottoes, China.

Other important Chinese grottoes are Turpan Grottoes, Fig. 7, and Xumishan Grottoes, Fig. 8. Both these areas of grottoes have been carved out of sandstone, and their artwork use the indigenous sandstone. The building of the approximately 130 grottoes in Xumishan took place over five Chinese dynastic eras, from the (A.D. 386-534) to the Tang (A.D. 618-906). Looking at the present-day natural sandstone artwork in the U.S.A., it is not difficult to imagine that the ancient Chinese took inspiration for their artistic and architectural creations from their natural environment as well.

Fig. 7. Turpan Grottoes, China. Fig. 8. Xumishan Grottoes, China.

The protection and restoration of these ancient and decaying grottoes are not inexpensive. In this endeavor, science and engineering can be used to provide a sustainability perspective that should not be ignored. The ancient Chinese did not have the benefit of modern science to educate them about sustainability. Indeed, in the case of the Mogao Grottoes, a monk named Yue Zun dreamed of 1000 golden Buddhas when he has traveling home across the region of the Mogao, and he decided to make his dream real by acting on it. The author can empathize with that because he had similar creative inspirations while travelling through the three national parks (not including the Grand Canyon) in southern Utah.

According to the United Kingdom minerals yearbook 2005, British Geological Survey,[1], the exergy content of the main extracted minerals is 3.94 E16 J for igneous rock, 5.96E14 J for sandstone and 3.65E11 J for talc. In other words, the sandstone does not have that much exergy to begin with, and maybe not too much value should be added to it even though it is relatively easy to work. For that very reason of it being relatively easy to shape and carve, sandstone is also relatively susceptible to the weathering by the sun, wind and water.

Thermal buffer capacity (TBC) of ecosystems has been previously proposed as an overall indicator of ecosystem integrity. Results have indicated that there is a difference between protected (low heat-up rate) and non-protected areas (high heat-up rate),[2]. Overall ranking suggests that the dominant ecological environment has the highest TBC of all surveyed land-use types. It is clear that many of the Chinese sandstone grotto areas are in high heat-up rate regions. High heat-up rate regions correlate to lower TBC regions.

References:

[1] BGS, United Kingdom minerals yearbook 2005, British Geological Survey, Keyworth, Nottingham (2006). Available at http://www.mineralsuk.com/britmin/ukmy2005.pdf.

[2] Aerts, R., Wagendorp, T., November, E., Behailu, M., Deckers, J. and Muys,B., “Ecosystem Thermal Buffer Capacity as an Indicator of the Restoration Status of Protected Areas in the Northern Ethiopian Highlands,” Restoration Ecology, Vol. 12, No.4, pp. 586-596, Dec. 2004.