Some of my most interesting adventures have not been planned, they have just… happened. Matiana cave, near Munda was one such event. It began in Jervis Bay, Australia, a friend told my wife Lyn and I of a cave he had heard about on his recent trip to Munda in the Solomon Islands. It wasnât for the untrained and the local divers were untrained in cave diving techniques. They had enough knowledge to treat the cave with great respect and were staying out. In their early attempts to enter the cave, silt near the entrance had been disturbed, rolling down behind them and causing much angst on their exit.
Contact was made with Marianne and Dave Cook at Munda, in the Western Provence, and to try to make arrangements for us to dive the cave during our trip to the Solomons. No confirmation had arrived before we left so we decided to take a small amount of gear for the dive, just in case it did happen.
It did. Sheltered beneath a towering limestone cliff on one side and a very protected lagoon on the other, the cave was originally discovered by local Solomon islanders looking for crayfish. A silty ramp leads from the surface, down to a tree stump at 30 metres. We followed a fixed line wisely laid by Mariana on her initial dive. The line began just below the surface and terminated at a stump near the cave entry.
Fixing a new line to the stump and passing beneath the overhang the water cleared; there was no silt. Hovering over a rock balcony, before us lay an enormous passage. Splitting off to the left, it appeared as a giant curving vertical rift in the solid rock. Beneath the balcony, the silt floor fell to greater depths, while the roof could not be seen.
Floating on our powerful beams of lights we leapt from the balcony into the cave proper, an overhanging ledge began to form on the right hand wall at a depth of 40m. As we moved along the ledge it became wider, then the cave revealed its secret, Matiana cave was once dry. Hanging from the ledge was a stalactite followed closely by a small shawl formed at the junction of the wall and the roof of the ledge.
Cave decorations such as these cannot form underwater. They form in voids (caves) in limestone rock when moisture leaches calcium carbonate from the rock into solution. Droplets of solution then migrate to the lowest point and slowly the water evaporates leaving solid calcium carbonate crystal, which over thousands of years grows into various beautifully shaped cave decorations.
My slightly narcosised mind tried hard to analyse what we had found and what it meant. Simple, the ocean was once at least 40m shallower than it is now and it stayed that way for a few thousand years.
The cave passage is not straight so I tied off the guideline to prevent it from wedging into crevasses or damaging smaller more delicate decorations. Other than smooth rock, the only structure available was a 100mm diameter stalactite. Once secured we move forward staying on the edge of the ledge. Delicate straws three to 10 millimetres in diameter begin to appear under the ledge. A small forest of straws has grown in much the same way as the stalactite. Unlike the stalactite where the solution passes over the structure, a straw has the solution of passing down through the centre much the same as a drinking straw.
Beneath us the floor of the cave was barely visible in our lights and we guessed it to be approximately 60m. Above, our bubbles continued to flow upward to an unseen ceiling. On the wall beneath the ledge, a beautiful formation appeared, probably formed as solution dripped and splashed from above allowing a chandelier of stone to evolve. Formations sometimes take on imaginative appearances, this one we believed looked like a cuttlefish and so it was named The Cuttlefish. Narcosis helps with these imaginative shapes, however, in this case we were able to later verify our muddled minds with our photos.
Forests of straws continued to cling to the underside of the ledge, it began to slope down and to become narrower, until it finally stopped at a broken column.
Water dripping from the roof forming a stalactite sometimes has a large enough flow to drip to the floor forming a stalagmite, a decoration growing from the floor up. Given time these two will meet and join. I believe that the column we found had already achieved this goal however at a later time a movement in the parent rock fractured the column back into their two individual structures again.
At 50m the broken column was the deepest we had seen. It was perched on a false floor beneath the ledge, with the real floor out of sight beneath us. Leaving the ledge our path was blocked by a rock fall from a gutter leading up towards the roof. This appeared to be the end of the cave passage in this direction, we were 80 metres from the balcony. New leads are possible, our dives were limited by decompression and used up mapping and photographing. More dives will be required to explore the cave fully. Many sections of the floor were too deep for us to see, so it is possible a deep passage may lead from near the floor.