New Zealand Caves

Hollow Hill cave has huge columns with strange "blade formations"

   The Peter Lambert  Level of Gardner's Gut has a big column, coloured red by rust.

   Splattered mud versus splattered lime water. (Hollow Hill cave)

Light suction in caves: phosphorescence and photography

  Page 4:  more caves.

Light suction in caves

Sign on a darkroom door

"You can never use too much electronic flash in a cave"
Bob Boas 

"Do not open: all the dark will leak out"

Electronic flash exposures are computed from the guide number. Slides of caverns  come back too dark, unless compensation is made  for caves losing photons.

When a flash is used outside, or in a large cavern, there is no reflection.

The 3/4 rule says:
flash guide numbers should be multiplied by 0.7  in a cave.

Cave phosphorescence

Caves do suck up some light, it is not just a charming metaphor!

Some cave minerals absorb UV and far blue light.
Outer shell electrons are elevated to a higher energy band (often in the conduction band) by absorbing light energy.
Conduction band electrons travel to electron traps and then jump back unpredictably to lower energy bands.
Characteristic radiation is emitted in the process, often in the visible spectrum. For example, calcite glows blue.

Phosphorescence fades exponentially after the flash.
Some of the energy is not in the visible spectrum and is lost as infrared or heat vibrations in the crystals. 
Phosphorescence is not all that efficient.

The caver's carbide lamp to the right shows the size of the "blades" projecting from the base of a large column in New Zealand's "Hollow Hill" cave.

But what are these blades? Are they huge "helectites" forming in a similar way to the small ones on the left?

Press the right image for a bigger one and the left image to return to page 2,  where helectites were described.

Castle Grotto,
Hollow Hill Cave

A stalactite emerges from the ceiling and fuses with the stalagmite below, to form a column.

The stalactite is standard and looks like thousands of similar structures, but the stalagmite component is covered in the big "blades".

In theory, the stalactite is the "parent" of the stalagmite in a column. The stalagmite formed from excess lime water the stalactite did not use. So why did the chemistry change to make blades only on the stalagmite?   Perhaps there a physical rather than a chemical explanation?

The whole brown column, and an adjacent white one like it, can be seen by pressing on this image - an impressive sight that is warmly recommended to all cave lovers.

The unfortunate explanation is that many cavers have tramped past this formation just to the left of the picture and mud from their boots has splattered onto the column.

Hollow Hill cave is one of the most beautiful in New Zealand and is very easy to walk into. This photograph was taken in 1964, before the cave was placed off limits to casual trampers.

In the dirty base of the column is this  attractive little pool.

The picture of a drop hitting the water was obtained by opening the camera shutter, listening to the steady drip, then firing the electronic flash at the time of impact. Actually,  it was slightly too late and I did not get the impact moment I wanted.

My theory is: the little rock "trees" around the edge of the pool  result from splash, as drips hit the pool and splatter the surroundings with lime water. You can see these "trees" better on the big version [press to see it].
The "trees"  have brown "leaves",  which is the spattered mud.

This image has been used in a Schering calendar and like all the others, it is copyright.

Press for bigger version.

Here  is a magnificent column in the Peter Lambert levels of Gardner's Gut cave, Waitomo, New Zealand.

This is how a column "should" look.

Imagine creating this structure by dripping candle wax around a bottle.
That was how we  made holders for table  lamps in the 1960's.

Dripping lime water explains this column, but does not work too well for the blades described above.

Around the base are round deposits where the "candle wax" missed the main column.

Peter Lambert was a famous New Zealand caver. Peter explored many of the Waitomo caves,  illustrated here. He was killed in a freak cave accident in Nelson.

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