Cave Entrances - Dusty Deposits

This article is about the thick deposits of dust often seen just inside cave entrances and discusses deliquescent mineral deposits in the entrances of Eastern Australian caves.

Sources of Dust
Tourist Do's and Don'ts


The earliest accounts of cave exploration in NSW record a large quantity of dust in dry cave entrances. In the 1800's people have written saying that they sank "up to their knees" in dust. With the passage of people, this dust usually becomes compacted and loses its soft qualities however in some tourist caves such as at Jenolan and Wombeyan (NSW) this dust can still be seen off the sides of the track and in little-visited areas. I have never encountered knee-deep dust, though.

Sources of dust

The origin of dust in dry cave entrances is usually ascribed to the wind (ie aeolian source) however there are other sources, depending on what the dust is made of.

Tourist Do's and Don'ts


The origins of deep dust in dry cave entrances is an interesting problem. It seems to be more prevalent in caves with multiple entrances, although it is also present in large caves with single entrances.
Lint is certainly a modern constituent of dust (N. Michie, pers. comm.) in tourist caves.
I wonder about the depth of dust as reported by the earlier accounts. I do not question the depth, rather I wonder why we do not find dust to that sort of depth these days. If the dust was due to the extrusive effect of nitre on cave sediments, then one can guess that there is no longer the quantity of nitre present in the cave entrances. One possibility is that the nitre was being formed from wallaby scats. These days, wallabies no longer inhabit the caves so possibly the source of dust is not being replenished.
I have looked at some very small holes in limestone, too small to call a cave, in which there was no dust, just turned-over soil as might be expected from (say) earthworms or insects.
I propose that in order for cave entrances to have dust, there needs to be:

These last two activities would need to be repeated in order for the dust to form, as distinct from soil.
In the case of Fig Tree Cave at Wombeyan (NSW), to test the hypothesis a number of measurements would need to be made:


Personal comments with Armstrong Osborne in 2000 and with Neville Michie in 1999.
Recently, the Australian Museum has analysed Niter and Sylvite from the dust in the Devils Coach House and the Grand Arch, Jenolan Caves. This was presented at the International Union of Speleology congress in Brazil in 2001 and will be in the Proceedings (in prep).
Hill & Forti
Speleology by George Moore and Nicholas Sullivan.

Cosmetic update, January 2006. Content updated 28th January 2002.

home speleothems cave zone by form cave minerals pseudokarst conservation articles about jill

entrance zone

Entrance Colours Wind Effects Craybacks Cave Coral Reflective Dots Entrance Dust Sharks Teeth Temperature Effects