Mysterious South American mounds are made of worm poop

I wonder if there are any paranoid alien theories about these mounds? Whoops, I might have just started one! :D

This ix an example of how small individual occurrances over a long period of time can have a large effect.

http://www.cbsnews.com/news/mysterious-south-american-mounds-are-made-of-worm-poop/

By Stephanie Pappas Livescience.com May 12, 2016

Large, mysterious mounds of soil found in the tropical grasslands of Los Llanos in South America finally have a scientific explanation: giant worms.

The mounds, found near the Orinoco River in Colombia and Venezuela, are called surales. Now, researchers have discovered that half of the mass of these dense soil piles is composed of earthworm excrement. The mounds form when worms -- many reaching more than 3 feet in length -- digest the dirt in the shallowly flooded grasslands of Los Llanos, researchers report May 11 in the journal PLOS ONE.

As they feed on the organic material in the soil, the worms excrete "casts," which are essentially worm poop. The casts pile up to form mounds 1.6 feet to 16.4 feet in diameter. The surales can grow as high as 6.5 feet tall.

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More questions remain, the researchers wrote, such as what happens when mounds eventually erode and collapse. Worm landscape formations are also known to be present in South Africa, Uganda and New Guinea, Iriarte and his colleagues wrote.