Resurfacing of underground peat fire: smouldering transition to flaming wildfire on litter surface

Abstract

Background Smouldering wildfires in peatlands are one of the largest and longest-lasting fire phenomena on Earth, but it is unclear whether such underground peat fires can resurface to the ground and ignite a flame on the litter layer. Methods This work conducted a laboratory experiment by putting a 5-cm thick litter layer (banyan tree leaves with a density of 27–53 kg/m3) onto a 10-cm thick peat sample (moisture content of 10–100%). Key results and conclusions Tests confirmed that a smouldering peat fire, ignited at the bottom, can propagate upwards and resurface to ignite a flaming wildfire on the surface litter layer. The propensity of litter to be flaming ignited decreased with increasing peat moisture content and litter layer density. We found the threshold of such surface flaming as a function of temperature and temperature increase rate at the interface between peat and litter. Finally, large field experiments successfully reproduced and validated the laboratory observations. Implications This work reveals an important wildfire ignition phenomenon that has received little attention but may cause new spot fires, accelerate fire progression and exacerbate its hazards.

The initiation of smouldering peat fire by a glowing firebrand

“…Smouldering peatland fires were brought to the forefront of scientific debate following the 1997 extreme haze event in south-east Asia from burning peatlands during a particularly strong El Nino season (Page et al 2002). Following this event, many research studies have targeted understanding the characteristics of smouldering peat fires, including combustion chemistry (Huang and Rein 2016), ignition (Lin et al 2019;Cui et al 2022;Santoso et al 2022), fire spread (Prat et al 2015;Yang and Chen 2018;Huang and Rein 2019;Qin et al 2022aQin et al , 2022bZhang et al 2024), emissions (Hu et al 2018;Kohlenberg et al 2018;Lin et al 2021b), detection (Atwood et al 2016;Rein et al 2017), and suppression (Ramadhan et al 2017;Santoso et al 2021;Mulyasih et al 2022). A recent review paper provided a comprehensive overview of smouldering wildfires, together with their associated environmental and health issues, as well as the challenges in prevention and mitigation (Rein and Huang 2021).…”