The river in Argentina that flows sideways

The Mocona Falls is in the northeast of Argentina, near the border with Brazil. Photo / Creative Commons image by Wikimedia user Leandro Kibisz

The Mocona Falls almost seems to defy logic.

The 2.4 kilometre-long waterfall forms when water levels lower along a split-level channel on the Uruguay River in Argentina, close to the border with Brazil.

The effect is of a river falling sideways — and it looks like a feature on an alien planet.

The waterfall, which is only visible for about 250 days per year, is almost 12 metres high in places.

When the river level drops, the falls appear - in some places, the drop is as much as 12 metres. Photo / Creative Commons image by Wikimedia user Leandro Kibisz

When the water levels are a bit higher, the river becomes rapids at this point.

Mocona means "that which swallows everything" — and these pictures show just why it was given such a dramatic name.

When the water rises, there are rapids at this point of the river. Photo / Creative Commons image by Flickr user Rachel Hugh