Thanks to a National Geographic-Waitt grant I was able to return to the ever fascinating Caversham sea caves to do some more survey and science work. I had an exhaustive list of goals, and while a great deal was accomplished, we were also very limited by the unseasonably poor swell conditions brought on by this year's atypical weather. There was not a single day appropriate to visit the rugged South Coast and the conditions were never appropriate for SCUBA diving. Surveying was a struggle and we often
We did managed to map 4 of the 10 longest sea caves in the world, surveying over 2 km of passage which is a monumental accomplishment given the survey conditions. I also collected shell samples for amino acid racemization dating and sand for OSL dating to provide age constraint on the +4m marine terraces, and thus the rate of cave formation, speleogenesis, and tectonic stability of the coast. I also employed the high-precision GPS I brought to determine the exact elevation of the +4m terraces. We surveyed and explored the first definitive karst formed cave in the Caversham Sandstone. We took extensive photos of the Cave of a Hundred Names to enable a 3D structure from motion (SfM) model to be created of the entire cave. We also made attempts to document the sea life present (including some rather interesting sponges and bryozoa) and took some good photos of the more interesting features of the caves. Ongoing work includes a kayak-mounted shallow bathymetry survey, cutting and polishing a large stalagmite (half for the Waikouaiti Museum and half for paleoclimate study), sending off samples for analysis, and drafting the cave surveys into proper maps.
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Easily one of the main highlights of the sea cave work was the last day of surveying in Skull Head Cave. Jeff and I just had a little bit of tie-up survey to do. The last passage left to survey, well into the cave, took off towards the sea from a four-way junction. It was a modest passage about a kayak in width, with surging flow and slight ledges on the side (one of those extreme low tide only passages). Usually these passages go 5-10m in and then end abruptly. Not this one! Jeff led the survey. Many tens of meters onward we reached a narrow bedrock passage (another sign of a typical passage end). Here however we had a faint glow of light in the distance and a slight draft. It headed out to an entrance! I was a bit perplexed where we were headed but we surveyed on, passing through increasingly nice (and very long) passage. Our 10 m of survey turned into hundreds of meters, cleanly pushing the length of Skull Head past the magic one kilometer mark (the second cave in the world to do this, its neighbor Matainaka being the first). To my surprise we ended up connecting into the Hall of Whispers Cave which features one of the nicest chambers on this coast. Rocks block the entrance at low tide so I had only been in this passage during higher tides when the key connecting passage would have been flooded. I was ecstatic that there was still more to discover on the Caversham caves.
World's Longest Sea Caves (as of November 2014)
1 Matainaka Cave Otago New Zealand 1540m
2 Skull Head Cave Otago New Zealand 1120m *
3 Erangi Point Cave Waitakere New Zealand 850m (est.)
4 Noisy Cave Otago New Zealand 563m *
5 Kotau Point Cave Waitakere New Zealand 485m (est.)
6 Mercer Bay Cave Waitakere New Zealand 470m
7 Gemma's Cave Otago New Zealand 421m *
8 Lamb of the Lost Cave Otago New Zealand 407m *
9 Pink Cathedral Cave Otago New Zealand 404m
10 Sea Lion Cave Oregon United States 401m
* surveyed November 2014 BOLD- Caversham cave (Barth et al. survey)
A lot more scientific work is on its way for the Caversham caves in the coming months. Photos of me by Jeff. Big thanks to Jeff Creamer for field assistance and National Geographic for funding.
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