Cathedral Cliffs

Accessibility: EASY
Eroded conglomerate and sandstone, Cathedral Cliffs. Photo/ K Pedley
Cathedral Cliffs viewpoint overlooks an impressive series of rock pillars formed by natural erosion by rainwater of the soft rock in the area.
Cathedral Cliffs. Photo/ D.L. Homer, GNS Science
The rocks comprise layers of soft sandstone and siltstone together with harder gravel deposits. Landforms like form what earth scientists call badlands topography, or in America, are often referred to as hoodoos. In other countries such badlands might occupy vast areas such as in Alberta (Canada), Utah and South Dakota (USA), but here at Gore Bay, they occur in just the small canyon area southwest of the community.

When the rain falls, the gravel layers form a more resistant layer which protects softer sediments below from being washed away. Sometimes all it takes is for a large stone positioned at the top of the pillar, to protect the softer sandstone and siltstone layers below from being eroded. Rainwater hits the gravel layer at the top of the pillar and flows vertically down to the base, and this forms the very marked vertical ribs forming the pillars a bit like cathedral spires. The brown-coloured rocks at Cathedral Gully are about 2 million years old and also occur in the coastal cliffs south of Gore Bay. They have not been eroded into pillars along the beach as younger sediments and soils overlie them in this area, protecting them from erosion.

How long do the pillars last? Individual pillars might last decades; others for only a few years before they a whittled down to a small stubble or fall over. The rate of erosion depends on the intensity and amount of rainfall and the degree of protection offered by the gravel. Once eroded, other pillars however form in their place, and there is ample rock available for the process to continue almost endlessly.
Cathedral Cliffs. Photo/ D.L. Homer, GNS Science
Observe how some layers in the cliffs have eroded more than others - the ones that stick out more are less prone to erosion. Can you see what grain size the less erodable layers are? Are they conglomerate or sandstone? Is it always the same type of rock? Conglomerates typically have big stones in the layers and represent what you might see in a typical river bed or delta today. Sandstone layers are literally made of sand sized stones as the name suggests! These therefore look much finer to the eye and have no big bits sticking out of the cliff face that you can see. Note also how some contacts between the conglomerate and sandstone layers are sharp and sudden, while others grade quite gradually between the different grain (stone) sizes. Why do you think that might be? What kind of sediment processes would form those different contacts?

Turn off east at Darrochs Rd or Hurunui Mouth Rd from SH1. Turn left onto Cathedral Rd. The viewpoint is signposted on Cathedral Rd when coming into Gore Bay from the south. Alternatively, turn off onto Gore Bay Rd from Cheviot township, continue south through Gore Bay settlement and the viewpoint is again signposted as you drive up the hill (road will now be called Cathedral Rd but it's essentially the same road!).

Take care crossing the road. While this is indeed a roadside locality, wheelchair access to the actual viewpoint is unfortunately halted by low wooden railings which need to be stepped over. Do not climb over the guard rail at the top of the cliffs!

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Accessibility: EASY

Please note the car park is on the other (south) side of the road from the viewpoint.

Sedimentary Active Erosion
Geological Age
Zealandia Evolution Sequence
Pākihi Supergoup: 5 million years ago – present
While there are many badlands style erosion examples around the world, one of the best examples is in Badlands National Park in the U.S.A., particularly noted for this form of erosion! Other NZ examples of badlands erosion include the Putangirua Pinnacles , and the Omarama Clay Cliffs