Celebrated around the world, the 4th Sunday of September is World Rivers Day. 
This is the Marokopa Falls, a 35 metre Fan waterfall created as the Marokopa River cascades over erosion-resistant Jurassic sedimentary strata.

The top of the waterfall marks the level of the Great New Zealand Unconformity where limestone rocks deposited about 30 million years ago directly overlie folded Jurassic strata deposited about 180 million years ago. 

The limestone rocks are easily weathered, dissolved, and eroded by the water, but as the river meets the less weatherable sedimentary rocks it cannot erode it as easily; creating the waterfall.

The Marokopa Falls are within the Tawarau Forest, just down the road from another famous New Zealand limestone landmark, the Waitomo Caves.

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- Matt Couldrey [geoid - digital geography]

Photo description: [black and white image of the Marokopa Falls; image taken by Matt Couldrey].