A pond of fly ash sludge at a Tennessee coal plant was breached earlier this week, and the toxic ash flooded out over 2.6 million cubic yards of the local landscape. This makes it officially larger than the Exxon Valez spill in terms of sheer size, though there's a big difference between the effects of this fly ash slurry and those of liquid oil in the ocean. The levels of toxins in fly ash and liquid oil are comparable.

The fly ash, collected from airborne pollution released in the making of coal, is quite dangerous for the environment, and locals report some areas are buried in up to 6 feet of ash. The biggest concern right now in terms of cleanup is keeping the slurry from reaching the Tennessee river, which feeds into the Mississippi and provides water for Tennessee, Alabama and Kentucky.

SOURCES: Scholars & Rogues (which links to a lot of other great sources) and AP News.

Photo via AP Photo/Wade Payne.

Send an email to Annalee Newitz, the author of this post, at annalee@io9.com.