"Clearly a sign of the end of days," wrote another. The woman who first spotted, however, told Insider that she thought it was "beautiful" and "unique." Others expressed curiosity over what might have caused the intriguing formation. Kevin Butt, a soil ecology expert at the University of Central Lancashire, said that he believes it can be attributed to a combination of heavy rain and the sidewalks being a hard surface. "In short, worms have likely come to the soil surface due to excess rainwater, have been unable to burrow down due to movement on to a hard surface and the shape seen may well be a function of the water draining away, rather than specific behavior of the earthworms," Butt told Insider.