Topic: Cliffs - Follow-ups

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PLEASE NOTE:  Dates recorded AFTER 18.9.2010 will be FOLLOW UPS ONLY as the Tongaporutu Project is now completed.

The follow ups will mostly be limited to the Three Sisters beach and the Four Brothers beach.  However, relevant evolutionary changes, or should anything major occur at any of the other locations, then they will also be recorded.

FOLLOW UPS TO THE MAIN TONGAPORUTU PROJECT.

PLEASE NOTE.   Any cliff/cave collapses that occur at the principal caves that I am documenting on either the Three Sisters beach or the Four Brothers beach will be documented in Section Five on Sea Caves.  They will not be duplicated here.

 

THE THREE SISTERS BEACH

2010

6 November 2010   

PHO2012-0581, PHO2012-0583

There was a full cliff face collapse at the small bay immediately north of the Three Sisters Cave.  This collapse destroyed a small, through going corridor cave in the process.  I believe this collapse was instigated by the Mega Storm that I observed on the 18th September.

At the rear of Elephant Rock, the two cliff collapse sites that I observed on 25.5.2009 and 30.1.2010, have undergone a further major loss of cliff material.  The loss was of such a magnitude that the two previously close but separate collapse sites are now co-joined.

It sometimes happens that multiple collapses can occur at a single or close but separate site(s) until the cliff in question finally achieves a state of equilibrium.

 

2011

20 March 2011  

PHO2012-0515

The cliff section collapse site appears to have stabilized for the time being.  This does not translate into it being stable however, as the northern part of it still has substantial material that will shed under the right conditions.  The New Sister is still attached to the parent cliff, but is undergoing carving action on its northern base.  This is possibly due to backwashing waves.

The cliff collapse immediately north of the Three Sisters cave that I observed on 6.11.2010, still has a largely intact debris field.  It does however appear to have had more material added to it.

The double barrelled cliff collapse to the rear and immediately south of Elephant Rock (PHO2012-0515), continues to shed large amounts of material and remains in an unstable state.

 

18 May 2011  

PHO2012-0620

The cliff section collapse site has lost more material since my last visit.  This has occurred at the northern end of the cliff section where a new arch was forming.  I didn’t photograph this.

At the double barrelled cliff collapse site to the rear and immediately south of Elephant Rock, this continues to shed more material.  The large rock debris field stretches right across to Elephant Rock (PHO2012-0620).

We have had a lot of rain lately so this has probably been a causal factor in the loss of more material at both cliff collapse sites.

 

3 July 2011  

PHO2012-0632

There had been a fresh cliff collapse at the northern end of the cliff section where a new arch (currently buried) had been forming.  (PHO2012-0632).

The double barrelled cliff collapse site to the rear of Elephant Rock appeared to have stabilized for the moment.

It is interesting to note, that while these two sites continue to lose material, plants cannot take hold.  This is important as plant roots help to stabilize the cliff material and give some protection against the sluicing effects of rain.  Without this ‘living carpet’, there is nothing to stop these cliff sites from continually eroding back.

 

THE POINT

2011

18 May 2011

Though it was a very low tide, due to big seas, I was unable to access beyond the Point.  However, through the gap that separates the Point from the Hole in the Rock on the Three Sisters Beach side, I did observe the remains of a cliff collapse in the form of a number of largish boulders and smaller rocks.

Until I can next access the Point, I cannot ascertain how large, or small this collapse was.

 

THE FOUR BROTHERS BEACH

2012

8 April 2012  

PHO2012-0652, PHO2012-0653

I observed a full cliff face collapse at the northern end of the beach.  It appeared to have occurred several months ago.  What particularly caught my attention though was the unique  narrow, ‘straight line’ rock strata formation visible in the top part of the exposed cliff wall.

 

GIBBS’ FISHING POINT

2011

27 April 2011  

PHO2012-0617-0618

A 2.7m high tide was due at 5.52 pm.  Despite it blowing a raging south-easterly gale in New Plymouth that rivalled Cyclone Bola in strength for a time, it was calm up at Tonga.  I had come up to escape the lengthy power cuts at home.  Though I brought up my camera, I wasn’t really enthusiastic about doing any photography.

I traipsed down to the Beach One end of Gibbs’ Fishing Point to have a look at things.  It was overcast with large areas of well defined cloud, but there were some blue areas of sky to lift my spirits.  I then walked along to the Four Brothers Beach end of the Point that overlooked the Wall.  As it was a south-easterly, visibility was good.

With it being calm with a roughly one metre swell running, I clambered down to the lowest point where a small stream exits over the cliff.  I set up the camera and took a couple of photos in overcast light that highlighted the Wall in its entirety.  A smallish hole had been punched into the lower part of the Wall.  (It had been there for a while).  This is tracking inwards towards Cathedral Cave.  Also, the ship’s bow feature at the base of the Wall is looking increasingly fragile and will carve off in the not too distant future.

Something that did surprise me was that when some of the fairly insignificant waves whoomped into the corner of the Wall at the right angle, then the cliff that I stood on experienced mild wave quakes.  I’ve experienced this shaking before during big storms, although the shaking was more pronounced.  I can’t say that I’d noticed it in calmer seas, probably because I don’t often photograph up here during such conditions.  Calm was probably relative, because though seeming to be calm here at Tonga, due to the ferocious conditions further south and further out to sea beyond the sheltering effect of the high hills, the sea state as a whole would have been highly energised.

I then took a couple of photos looking out to sea that included part of the eroded cliff.  The salt spray ‘fog’ at the horizon line was backlit against the cloud.  Shortly after, the sun shone through a hole in the cloud closer in and I got some shots of the Wall and the Four Brothers Beach in nice light.  I then went down to the Beach One end of the Fishing Point and took a couple of shots looking along Beach One, also in good light.  (See Section Two on Weather).

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