Tarawera Falls I

Tarawera Falls, Kawerau, New Zealand.

"The cliff in front of you is the end of an ancient rhyolitic lava flow that is believed to have poured from an erupting Mt Tarawera about 11,000 years ago. The high cliffs have resulted from rapid erosion of the thick lava flow, mostly occurring when great floods have passed down the river.

The lava is highly fractured and the river flows downwards through joints in the rock. About 30 metres back from the clifftop the Tarawera River disappears into subterranean chambers, re-emerging through the rock face in front of you."
From the information board in front of the falls.