The waterfall is the long-term result of a volcanic eruption that happened around 2 million years ago that spewed lava down a river valley, which then solidified over the older sandstone. This harder basalt then remained intact as water flowed over it and cut a deep pool in the softer sandstone underneath. The plunge from the top goes down 55 meters into a large 5-metre deep pool before it disappears into the thick bush.
The Tawhai Falls tumble over the edge of an ancient lava flow which erupted from Ruapehu many thousands of years ago.
