The effects of fire on rock weathering: some further considerations of laboratory experimental simulation

Abstract

Fire in the natural environment is a widespread agent of geomorphological and biological change. Temperatures can exceed 1000 C. There is often a rapid rise from ambient conditions through a steep thermal gradient, promoting rock disintegration. Laboratory simulation studies have established that temperature changes which are representative of natural fires affect rock material properties, which can then be related to weathering susceptibility. This study extends previous work by more closely replicating the natural environment, (a) through the simulation of rainfall and (b) by encasing samples to reflect the exposure of a single rock face to a passing fire event. Rock samples collected on Cyprus were prepared and tested following previously reported procedures. Change in modulus of elasticity was monitored using a non-destructive ultrasonic method. The data corroborate previous work but with somewhat different degrees of change. The new results are more likely to be representative of natural conditions and real-world change. The rate of rock disintegration and effects such as casehardening appear to be a function of rock thermal characteristics, material properties and environmental constraints such as diurnal temperature range.

Evolution of surface properties of ornamental granitoids exposed to high temperatures

“…The first studies of the effect of high temperatures on building stone focused on the variation of bulk mechanical properties in crystalline stones and colour changes due to iron oxidation in sedimentary stones [3,8,9]. From this initial focus on macroscopic variations, research in the last years drifted to assessing mineralogical and textural changes and their effect in building stones [10][11][12][13][14][15][16][17][18][19][20][21][22][23]. Most of these studies focused on the effects of temperature increase, without taking into account ashes and fumes, and therefore were carried out in furnaces on relatively large samples [e.g.…”

“…Most of these studies focused on the effects of temperature increase, without taking into account ashes and fumes, and therefore were carried out in furnaces on relatively large samples [e.g. [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25]. Commonly, samples were heated with different rates, kept at constant temperatures during a certain time interval and then cooled down freely.…”

“…Commonly, samples were heated with different rates, kept at constant temperatures during a certain time interval and then cooled down freely. Sometimes, the focus was on thermal shock produced by spraying or by immersion in cold water [11,25] or the consequences of localized heat, such as the effect of fire jet to induce flamed artificial finishing of building stone [26] or lasers as a way of reproducing heating effects in small samples [27]. Although these laboratory studies were sometimes complemented with studies of samples burnt in real fires of historical monuments [9,12,13,17,18] there is still few laboratory research on the effects of ''real fires", i.e.…”

Granitic Boulder Erosion Caused by Chaparral Wildfire: Implications for Cosmogenic Radionuclide Dating of Bedrock Surfaces

“…Temperatures in low-and moderate-severity wildfires in chaparral have been measured at 2257 and 4307C, respectively (DeBano et al 1998). Granitic rocks exposed to lowseverity wildfires would be expected to experience a decrease in their modulus of elasticity (Goudie et al 1992;Allison and Goudie 1994;Allison and Bristow 1999), likely as a result of microfracturing, but may not exhibit extensive spalling (Blackwelder 1927).…”

Wildfire impacts on the processes that generate debris flows in burned watersheds

“…Fire-induced rock weathering produces development of fractures that are generally parallel to the rock surface, and spalling and cracking of rocks of all sizes, including boulders, caused by high temperatures are often observed in burned areas (Blackwelder 1927;Ollier and Ash 1983;Allison and Bristow 1999). This physical weathering may combine with chemical weathering processes to produce a greater amount of materials available to be transported during rainstorms than would be available otherwise (Garfi' et al 2007;Ollier et al 2007).…”