Visitors enjoy their moment on a round-shaped ice block spinning on a frozen river in Tieling City, northeast China's Liaoning Province on Jan. 6, 2019. /VCG Photo 

A rare natural phenomenon, an ice disk like this usually occurs in slow-moving water in cold climates under the right conditions. /VCG Photo

It was previously assumed that the phenomenon was caused by water currents, but more recently, researchers have linked it to the water temperature at the site. /VCG Photo

In a 2016 study, researchers speculated that the formation of round-shaped ice block may be linked to a vortex underneath the ice formed by the changing temperature when less dense and warm water interacts with the frozen surface. /VCG Photo