Surface Mechanical Effects of Wildfires on Rocks in Climbing Areas

Wildfires are widely recognized as a cause of mechanical damage to rocks. Nevertheless, previous research has neglected how wildfires might impact sport climbing areas. In Spain, two large wildfires affected two climbing areas between 2020 and 2021. This paper addresses the rock mechanical effects of wildfires that could lead to safety issues, such as rock falls, climbing hold deterioration, and climbing anchor damage. In this study, the Non-Destructive Techniques (NDTs) of Ultrasonic Pulse Velocity (UPV) and Schmidt Hammer (SH) were used, and two types of measurements were carried out: randomized grid measurements and measurements along the climbing routes. Two phenomena were recognized: (a) thermal breakdown and (b) mineralogical changes. The results of using the SH show a relationship between the decrease in the rebound value and the observed mechanical damage. Field observations showed mechanical weathering, such as cracking, spalling, granular disaggregation, and thermochemical weathering with different temperature thresholds. Observed thermochemical reactions included reddening, CaCO3 calcination, rock decomposition, and quartz cracking. The set of changes involves a major rock outcrop transformation and an acceleration of fire-induced weathering processes. Both areas exhibited more effects at the bottom of the wall. Furthermore, in this paper, we explore how iconic climbing routes can be considered a form of cultural heritage and the consequences of their loss.