The rocky river swept through New Zealand gorge after a great storm

The rocky sandstone river flows along a gorge in New Zealand due to the impact of Gita.

Granular flow is quite a common phenomenon.

The phenomenon called "granular flow" was recorded in Terrible Gully near Canterbury, New Zealand, after the tropical storm Gita, Stuff.co.nz reported on February 21. This phenomenon occurs when stones of the same size are pushed together in large numbers down the slope, causing them to move like liquid.

Granular flow is quite a common phenomenon, according to geologist Dave Petley at Sheffield University."Basically pebbles react like particles, allowing fluid-like movement to occur. Of course, the density of this liquid is higher than liquid like water and particles are many times larger, but the river Stone can still produce liquid texture like we see in water, " Petley explains.

"It made a really loud sound like a truck full of gravel dumping all over the ground," said Donna Field, who filmed and shared. Sandstone is very easy to erode during storms.