Assessing the Impact of Wildfires and High Temperature on Rock Properties on Diverse Lithologies in the Czech Republic

Wildfires are an increasing global concern due to their profound impact on the environment and human life. These events affect a wide range of environments, from arid regions and forests to other highly flammable areas, such as the Bohemian Switzerland National Park in the Czech Republic. In 2022, a large-scale wildfire in this region—characterized by its sandstone rock formations near the Czech-German border—highlighted the importance of understanding the effects of extreme temperatures on rock properties. While wildfires occur almost annually in this region, the unprecedented scale of this event may have been exacerbated by factors such as wind and prolonged hot climate conditions influenced by ongoing climate change.

To investigate the impact of high temperatures on rock properties, we collected rock samples representing all major lithologies across Czechia, including sandstone and crystalline rocks. After preparing the samples, we exposed them to a controlled heating process, mimicking wildfire conditions. Samples were first dried at 105°C and then incrementally heated to 200°C, 400°C, 600°C, and 800°C, with ultrasonic P- and S-wave testing performed after each temperature stage to assess their dynamic elastic properties. The heating process was carefully designed to replicate natural wildfire conditions, including gradual temperature increases, targeted temperature suspension, and subsequent cooling.

Our findings reveal distinct thermal responses in rock properties. Sandstone and crystalline samples initially strengthened after heating to 200°C, likely due to changes in cementation. Beyond this point, progressive weakening occurred, with rocks reaching their weakest state at 800°C. These results align with previous studies, offering valuable insights into the thermal behavior of rock materials under wildfire conditions and contributing to a broader understanding of the environmental impacts of high-temperature events.