Cave Rock Surface Temperature Evaluation Using Non-Contact Measurement Methods

Abstract

The aim of this study was to evaluate the rock surface temperature (RST) regime in Kateřinská Cave in the Moravian Karst (Czech Republic, South Moravia) using nondestructive infrared methods. Air temperature monitoring was also included to quantify the dominant factors affecting the RST. Measurements were taken during the period covering January, 2010 to March, 2012. HOBO air temperature sensors with data loggers were placed in front of the cave entrance, in the entrance corridor and on selected sites in the cave interior. An infrared (IR) thermometer was used to measure the surface temperature of the solid rock. The RST in the cave interior during each season was also recorded by IR camera. The average temperature of the rock surface over the two year period was 6.95 °C. The longterm average of the RST was always 0.01 to 0.79 °C lower than the air temperature. The dynamics of the RST are most obvious at the entrance corridor to the cave, with temperature variability up to 17.34 °C. The dynamism of both the RST and air temperature decrease as the distance from the entrance increases. The lowest RST variability (1.19 °C) was detected at a distance of 271–280 meters from the entrance. The differences in the maximum RST in the monitored profile were relative small, ranging from 7.30 to 8.70 °C. Minimum temperatures in the cold season showed a significant difference among themselves. Changes in rock surface and air temperatures are dominantly influenced by air exchange with the external environment, although the RST may be locally influenced on a short-term basis by other factors, such as attendance and biota. Temperature heterogeneous zones over space in Kateřinská Cave with no air flow were located by thermal imaging. It is therefore an area where unknown spaces or exterior access can be expected.