Waireinga/Bridal Veil Falls

Bridal Veil Falls cascade over the edge of a thick basalt lava flow (Okete Volcanic Formation) that was erupted from a volcano about 1.5 km away, 2 million years ago. The lava flowed down a valley and ponded here in a wide part of that valley. As the molten lava cooled, the outside parts cooled and solidified first, at the top and bottom parts of the flow. As liquid lava solidifies to rock it contracts and cooling cracks are formed. These are usually oriented perpendicular to the cooling surface. They often form columns. The columns are usually oriented vertically in a lava flow as the cooling surfaces are the horizontal top and bottom of the flow. You can see some vertical columns in parts of this flow, but in other parts the columns have been bent around and are sloping. This is believed to have been produced by the lava still moving slowly as the columns formed and rotating them from vertical to these low angles.
The falls have eroded right through the flow and down into softer Oligocene (~30 milliopn years old) sedimentary rocks beneath. The hard basalt is what is creating the waterfall. Erosion of the basalt is mostly as a result of the columns becoming loose and falling out of the face.

Look at the bend and slope of the columns in the waterfall face - can you work out which way the lava flow was flowing?
Can you see any of the hard basalt at the foot of the falls - what shape and size are these rocks? Does this tell you how the waterfall is eroding back?