Deep Underground, Miles of Hidden Wildfires Rage - TIME

As far as 90 feet underground and 100 feet thick, miles of coal seams are continually burning in the U.S. and elsewhere, releasing toxic fumes that funnel up to the surface

Deadly Colorado blaze renews focus on underground coal fires

13.7M Hectares Burned: 236 Wildfires Still Rage Through Canada's Northwest Territories : r/climatechange

Skyrim: 25 Hidden Bosses (& How To Find Them)

Ibarra JoséV Muñoz Edgar Moliner Rafael June 1996 FTIR study of the evolution

Deadly Colorado blaze renews focus on underground coal fires - Los Angeles Times

Spontaneous combustion of coal seams in the Bengiler coal mine in Turkey

600 miles of tunnels: Homeless staying underground in Las Vegas share stories

Јамски пожар — Википедија

More than 1 million acres have burned in California since July as monster fires rage around Bay Area

Photos: Wildfires rage in Northern California

Underground Coal Seams Can Spontaneously Combust And Burn For Decades. Here's How Officials Keep Colorado's 38 Fires Under Control

The Ally From Hell - The Atlantic

Coal-seam fire - Wikipedia

Neighborhoods: The Hidden Cities Of San Francisco: The Fillmore, The Hidden Cities of San Francisco: The Fillmore

Greece tames wildfire near Athens, new blazes rage in 'tough' Mediterranean summer