Extreme environmental conditions in coal mine fire collapse structures

Coal fires are common in Earth's history and are associated with past climate change events1,2. Worldwide, more than 1 gigatonne of coal burns uncontrollably, resulting from natural chemical reactions and mining activities3–7. Here we show that collieries in East Jharia, India, present coal fire-induced collapse structures, up to ten metres in diameter. Field examination supported by mineralogical and microstructural analysis, and coupled flow numerical modelling, shows larger isolated collapse structures to be the most thermally active and high emitters of combustion gas and heat to the atmosphere. The presence of nanometre-thick iron-rich monolayers indicates extreme temperature gas/solid interactions analogous to those experienced by meteoroids entering the Earth’s atmosphere8. Collapse structures appear to support temperatures of ≤4000 °C, emissions of >7.0 ± 1.4×102 megatonnes CO2 equivalent and heat energy of 1.16 ± 0.23 ×108 megawatt hours/year. These emissions are nearly twice those reported for UK territory in 20239. Large collapse structures drive extreme heat and high carbon dioxide equivalent emissions while closely spaced ones suppress combustion, according to field observations, microstructural analysis and coupled flow modelling that revealed their temperature and gas release behaviour.