Moving moss

In glacial landscapes across the world, small balls of moss form, oval in shape, and tumble simultaneously as the glaciers melt, as if moving in a herd.

Known as “glacier mice”, these moss balls are understudied, but recently researchers have taken notice of them and their weird, herd-like behaviour^[1]. This has led to all sorts of questions and a couple of published papers on the phenomenon, such as...

How do they form?

Researchers have theorised that the moss balls form through “nucleation” at rough points on the glacier surface – just as crystals start growing on impurities in their containers. First, one crystal or drifting moss fragment attaches, and then others attach onto that, gradually coming together to make the shape of the final structure. It’s not clear how this always leads to oval balls, and none of them are round, but it does generally make sense as a theory.