Understanding Zombie Fires: The Hidden Threat of Underground Blazes
Zombie fires, or peat fires, are underground blazes that can burn for months or years, releasing significant greenhouse gases. They form in peatlands, which are increasingly vulnerable due to climate change and human activity. Efforts to combat these fires include controlled burns and preventing peatland drainage to maintain moisture and reduce fire risk.
In 1997, a fire ignited in Indonesia that would rage for almost a year, covering several thousand square kilometers. This fire halted numerous international flights and spread a thick haze all the way to China. Remarkably, despite being one of the largest fires in recorded history, it burned for months without visible flames, existing entirely underground. This phenomenon is not unique; each year, subterranean fires, often referred to as zombie fires, produce approximately 15% of global greenhouse gas emissions—six times more than international aviation. This raises critical questions: How do these bizarre blazes form, and is it possible to extinguish them?
The Science Behind Fire
To understand zombie fires, we first need to grasp the basic requirements for a standard fire: fuel, heat, and oxygen. Every type of fuel has an ignition point—the temperature at which it begins to break down. This breakdown process, known as pyrolysis, releases gaseous compounds that mix with nearby oxygen molecules, resulting in combustion. This chemical reaction produces heat and light, typically seen as flames.
However, not all combustion results in flames. Pyrolysis leaves behind a solid material called char, similar to charcoal. Char is devoid of combustible gases but is rich in highly flammable carbon. Under sufficiently hot conditions, the surface of char can react with surrounding oxygen, leading to a slow, glowing burn known as smoldering. This process emits smoke filled with harmful emissions, including carbon monoxide, methane, and particulate matter.
The Formation of Zombie Fires
Zombie fires, scientifically known as peat fires, occur in peatlands—soils that form when organic matter accumulates faster than it decomposes. Peatlands are typically found in cold or wet regions, where decomposition is slowed. When plants die in these areas, the carbon they absorbed during their lifetime becomes locked in the peat, making these regions significant natural carbon stores.
Historically, the moisture and cold temperatures of peatlands made them resistant to fires. However, climate change has led to increased droughts, drying out these landscapes. Additionally, many peatlands have been drained for agricultural purposes. Under these conditions, a surface fire can ignite the peat below, converting it into char, which continues to smolder. As heat builds in the soil, it further dries the peat, causing deeper layers to ignite.
Peat fires are slow-moving, advancing at a rate of just one millimeter per minute. Yet, their persistence is alarming; they can burn for months or even years, releasing smoke laden with toxic gases. Because they show few signs of burning above ground, these fires are incredibly challenging to detect until they ignite dry surface soil, potentially miles away from the original source. Remarkably, zombie fires can even smolder beneath snow-covered soil, lying dormant until they reignite in the spring.
