Jam Roll Bay VIRTUAL

This secluded bay near Te Puia and Te Kawau Pa is seldom visited due to its difficult access. In this virtual trip, you can navigate your way around our 3D model. Click on the numbered points to bring up more information and pictures. Spectacular folds and complex deformation can be seen in the orange-coloured sandstone and finer-grained, grey coloured siltstones. Both rock types represent sediments that were laid down in an ancient sea about 10 million years ago. We know that they would have originally been deposited in fairly flat or gently sloping layers, just like the modern-day seabed off the coast of Taranaki. However, these originally flat layers are now folded, rolled up and squashed - what could have caused them to become so deformed?

Scientists believe that the sandstones and siltstones were part of a submarine landslide 10 million years ago. Just like slips and rock falls on land, any part of the seafloor that slopes can potentially fail and become a submarine landslide. When submarine landslides happen, sediments start slipping and sliding downslope to the deep ocean. Along the way they are subjected to strong forces. Because the sandstone and siltstone was still soft and waterlogged when the submarine landslide happened, they were squished and squeezed into these amazing formations. After coming to rest, they were eventually buried by other sediments, and turned into hard rocks over time.

Take a look at the Jam Roll. Here layers of rock are completely rolled around each other just like a real jam roll. In the core of the Jam Roll you can see that some rock layers are the same thickness all around (a bit like the sponge cake), while other layers are squished and look gooey (a bit like the jam!). Geologists call structures like this a slump fold.

There is also a beautiful sea stack here at Jam Roll Bay. More amazing folds are seen in the sea stack, including a recumbent fold, which form when soft sediments are subjected to so much stress that they fold completely back over themselves. These folds often occur in submarine landslides, as the sediments are pushed and crushed on their way downslope.