Topic: Caves - Pilot Point
PILOT POINT CAVE - Pilot Point
Pilot Point starts at the southern end of Rapanui South. The Pilot Point cave being the transition point. Pilot Point’s southern boundary is the northern side of the Tongaporutu River. It also includes the large dune area that lies due east.
There is only one cave that I am documenting at Pilot Point and this is on the true seaward (western) side. There are a number of quite large blind caves on the southern Tongaporutu River side, but I am not making individual studies of them.
The term ‘cave’ is applied more loosely at this site as it includes several features that for my purposes are all inclusive. At the south-western end or boundary there is a forming blind cave. This leads immediately north (looking landward with your back to the sea) to a largish, solid arch. Just past this there is a narrow forming blind corridor cave and this leads around to the cave proper. The cave proper has three pillars that protrude from the cliff. Leading immediately north again, there is a through passageway or corridor cave that bisects a promontory. The cliff overhang and this family of interconnecting smallish caves I collectively call the Pilot Point Cave. Most of my documentation has been of the arch and the middle cave with three pillars. I have also observed how the beach changes here, plus the erosion processes.
The Pilot Point cave is where the Tongaporutu Project started.
27.4.2003 PHO2007-189-192, PHO2008-879-883,
This was my first visit to the Pilot Point side of the river. After exploring the cave area, I sat on one of the two large boulders that were at the base of the cave arch and had a bite to eat. After that I did some photography. At one point, while photographing a particularly nice rock in low light that necessitated a slow shutter speed, the tripod head refused to lock. Cursing, I decided to return in a fortnight with a repaired tripod and re-photograph the rock. (Note: I was so ignorant at this time that I had no idea one of the large boulders I sat on had probably fallen down from the cliff above during the past 24 hours – 12.7.2009).
18.5.2003 PHO2007-199-200, 203, 314
My first reaction upon reaching the cave was one of stunned astonishment. The large boulders beneath the arch had vanished, as in VANISHED. Not just disintegrated and scattered, but gone. The lovely, flattish white rock I had wanted to re-photograph again with the rock pillars had also gone. Everything was different.
This was the catalyst for the Impermanence: The Tongaporutu Coastline Project. Specifically, I would document the changes that were occurring along the Tongaporutu coastline at least once a month for an initial period of one year. In a way, the project chose me. I just happened to be in the right place at the right time when everything came together.
PHO2008-200 shows the through-going corridor cave. This is sited at the northern end of the Pilot Point cave system. Its darkened entrance is visible through the arch in PHO2008-199.
PHO2007-203 shows some of the blind caves on the south-western side of Pilot Point. This fronts onto the Tongaporutu River.
1.6.2003 PHO2007-315-316, PHO2008-890
The sand had been scoured out and lots of small rocks were exposed at the cave where previously they had been covered with sand. I estimated around a foot of sand had been removed.
30.6.2003 PHO2008-033-035, 927
The sand is well built up again. Only the tops of two rocks were visible where previously there had been many. No other changes of note, except that I re-discovered the white rock I had originally photographed with the faulty tripod on 27.4.03. It had been covered by sand and was now uncovered in a pool of water. Its position had changed as well as its appearance.
13.7.2003 PHO2008-054, 943
Very low sand level. Lots of rocks exposed at the arch. It appeared as if some of the arch had come away. PHO2008-943 is a location shot. The heavily shaded area of cliff to the left is the Pilot Point cave system. A forming blind cave is just to the right.
High sand level. No rocks visible. PHO2008-079 gives an expansive view of the cave system. The cliff promontory in the centre of the photo houses the arch (obscured from view).
I noticed lots of flotsam on my way to the cave. Seaweed, branches, flax, etc. I later discovered their source – a cliff collapse at the Four Brothers Beach. At the cave, the beach floor was completely bare. That is because the sand level was the highest I have seen it so far.
The cave itself was gouged right out, down to the bedrock with lots of middling boulders fully exposed. It is the lowest I have seen it. Where does all the sand go? (This was the question I asked at the time). This extreme scouring was most probably caused by the alpha storm that I observed on 29.9.03.
CLIFF SEQUENCING. This shows the cliffs that house the Pilot Point cave system.
20.12.2003 PHO2008-474-475, 1168
At the cave archway, there were lots of quite white looking roundish, smooth small boulders. I noticed that a number of the ones close to the cliff chambers had got green algae growing on them. This means that these rocks have remained uncovered since the alpha storm event of 29.9.03. I also photographed the curved wall that leads to the small forming blind cave on the south-western boundary of the cave system. (PHO2008-475). PHO2008-1168 shows a small blind cave on the southern side of the arch.
Very high sand level. No rocks were visible. There had been a minor cliff fall at the south-western forming blind cave. There were four medium sized rocks. I estimated the minor cliff fall had occurred within the past 24 hours due to the rocks pristine condition. That is they have jagged not rounded edges as would be expected with water carving.
7.3.2004 PHO2008-717, 1223
Just as I had expected, the minor cliff fall material I saw on 4.2.04 had disappeared. (PHO2008-1223). Of the cave itself, the sand level was very high, no rocks were visible.
19.4.2004 PHO2008-794, 796-797
Medium sand level, some rocks were visible. Partial wave destruction was evident above the largest of the three rock pillars. (The northern one). There was a debris field at the pillar’s base. PHO2008-794 shows the arch from its southern side while PHO2008-797 shows the arch from its northern, main cave side.
Following on from 19.4.04, further wave destruction was evident, now on the northern rock pillar itself. The sand level was medium. Lastly, there were two rocks below the arch. I didn’t notice them on 19.4.04. After that, I said bye bye to the cave. Don’t know if or when I will see it again. Felt quite sad really. (Note: This was the end of the year long project which culminated in a photographic exhibition at Puke Ariki later that year. I hadn’t at that time decided what to do with regards to continuing the project – 12.7.2009).
Little change from 2.5.04, except that the sand level was relatively high. The wave damage to the northern rock pillar is clearly visible.
There were a lot of logs and driftwood at the cave, specifically on the southern side of the arch. It was the most I have seen.
11.12.2005 PHO2008-1526, 1528-1529, 1531
The logs and driftwood had gone walkabout. The arch had some bits chomped out of it, and more damage was visible above the rock pillars. I also photographed several of the blind caves on the Tongaporutu River side of Pilot Point.
A large number of rocks lay close to the three rock pillars. They had probably tumbled down during the past week.
20.4.2008 PHO2011-1218, 1221
High sand level. The northern rock pillar has now been destroyed. Judging by the state of the rock slabs and sand, I guessed that it had been destroyed at the same time as the two cliff collapses near Pilot Point arch that I observed from the Three Sisters Beach side on 6.4.08. There had also been a cave roof collapse on the Tonga River side of the Pilot Point arch. (PHO2011-1218). There are several blind caves here.
20.7.2008 PHO2011-1254, 1256, 1259
SUPER-STORM EVENT. Super-Storm One. There had been a full cliff face collapse at the cave. From what I could see, the arch had been mostly destroyed. A huge amount of soil and large, pristine boulders were present. The debris field extended a fair way seaward. Such was the amount of material, I couldn’t tell whether the remaining two rock pillars at the cave proper, had survived. The south-western forming blind cave was intact as was the northern passageway cave.
According to the O’Sullivans who felt the earthquakes, the Pilot Point arch collapsed at about 9.30 pm of the 19th, and the cave collapse had occurred around 1 pm on the day of my visit, the 20th. I believe that the cave collapse, along with the other cliff collapse on the Tongaporutu River side, was caused by a ripple effect, triggered by the more massive, primary cliff collapse that destroyed the Pilot Point arch.
SUPER-STORM EVENT. Super-Storm Three. At the cave, some large boulders remained, but these aside, most of the cliff debris and all of the soil had either been smashed up further or gone altogether. At the arch site, a new rock stack had formed. There were broken rocks on its top. I have nicknamed it Pat’s Stack as I am most likely the first person to have seen it. Due to its location it will probably be quite short-lived geologically speaking. Of the cave’s previous two surviving rock pillars, the middle one has lost a fair amount of material while the southern pillar for the most part has survived.
31.8.2008 PHO2011-1314, 1316
More of the smaller rocks migrated further seaward or had gone altogether. The larger boulders, both mudstone and sandstone ones mostly remained close to the cave. The two rock pillars, though having lost their top parts, still remained. The cliff immediately above them was now quite clean, revealing the true scale of the massive cliff collapse.
12.11.2008 PHO2011-1314, 1316
CLIFF SEQUENCING. Most of the 20.7.08 cliff collapse material had now dissipated, apart from a few large boulders. These were possibly saved by being partially anchored in the sand. Pat’s stack appeared to have reduced in height. Most likely due to its top cap of loose rocks having been dislodged by waves. With the cliff sequencing, the external location is shown in contrast to the mostly close-up views.
A lot of the rocks from the cave collapse site of 20.7.08 had migrated quite a way out to sea. Some of the larger boulders still remained, although they are well rounded,
worn down and partially buried in the sand. The two rock pillars still survive with the indented cave being prominent on either side of them.
As this project proper is about to finish, I wanted to all but end it where the project had began – here at the Pilot Point Cave. Though the weather was wet and unpleasant, at least the light was even. With the panoramic camera I was able to get the whole of the Pilot Point cave system, including Pat’s Stack in the one frame. Of the cave proper with its fluted columns, these had all but been destroyed. In fact you couldn’t now really class it as a cave system at all because so much of it has gone. Quite sad really.
N.B. The photos taken on the 27th June didn’t come out so I will have to re-do them under better weather conditions. (26.7.2010).
The Pilot Point Cave system is virtually unrecognisable from when this Project first started on 27.4.2003. As the sun was out and part of the cave was in the shade, I took a landscape photo from mid-way down the beach. This shows the ‘cliff-scape’ environment where the cave system is located. Pat’s Stack, the collapsed arch remnant, is clearly visible. (This was created during the tsunami of destruction that occurred during a super-storm event in July 2008).