Joint Symposium
Australian and New Zealand Association for the Advancement of Science
and
The Royal Society of NSW
Recent Research on Limestone Caves
Lectures byCraig Barnes, Jill Rowling and Neville Michie
Date: Wednesday 4th November
Location: Australian Museum
ABSTRACTS
Radon in Caves
Dr Craig BarnesSchool of Chemistry, The University of Sydney
Radon is a radioactive gas, and we are exposed to it every day. Indeed, radon is the main contributor to "normal" background radiation levels that we are all exposed to. However, for the thousands of people that visit caves each year, the presence of this heavy radioactive gas is a point of concern.
Various methods of detection and measurement of radon levels in caves have been used throughout the world over recent years, including those based on track etch films, scintillation cells, ionisation chambers and solid state detectors. The results obtained from such measurements have been analysed, firstly, to see if dangerous levels of radon are in evidence and, secondly, to better understand the mechanisms behind the fluctuations observed in the radon levels.
By comparing results from the same site taken at different times of the day and year, it has proved possible to observe both diurnal and seasonal variations in radon levels. Alternatively, comparison of results between sites has allowed a determination of the spatial distribution of the radon levels within the caves and the characterisation of radon behaviour. More importantly, the sources of radon with cave systems have been narrowed down, providing information towards possible management procedures.
"Ribbon Helictites"
Jill Rowling.In August 1997 a poster, entitled "Ribbon Helictites from Jenolan Caves, NSW Australia" was presented by the author at the International Union of Speleology conference in Switzerland. Since then, further work has been undertaken (Helictite 36(1):3-10, 1999) to unravel the secrets of the formation of ribbon helictites. In particular, SEM photographs of the surface of one ribbon helictite has shown an unusual crystal form (for calcite), together with etching and pitting of surfaces. These surfaces exhibit some features found in organically deposited calcite.
Further optical work has revealed that the stem of ribbon helictites is comprised of a twinned pair of crystal aggregates, with the stem's central canal lying in this plane. The ribbon, too, may exhibit twinning. Ovals on the ribbon's surface are twinned aggregates, associated with a disruption of the ribbon's central canal.
The talk proposes growth mechanisms for ribbon helictites, and also discusses related forms.
Research on Physical Processes in Caves.
Neville MichieInvestigations of some physical processes in caves have shown a range of contrasting relationships with surface processes. The scales over which these processes operate are quite different to surface processes. The main processes examined here are heat and mass transport, which are often coupled. The mass transport includes moisture and aerosols.
Study of these processes has required the development of special instruments that can accommodate the unusual scales over which the processes operate. The investigation of these processes has provided new information useful for the protection of caves from human impacts
Report on the Lectures
by Dr Michael Lake,Hon.Sec., RSNSW
This General Monthly meeting was a joint Symposium with ANZAAS with the theme of "Recent Research in Limestone Caves".
Neville Michie spoke first on "Physical Processes in Caves". These processes are generally very slow and low energy; the geothermal flux for instance is orders of magnitude lower than it is on the surface and the air flow in caves can be so slow as to be unoticed except to sensitive measuring instruments. Yet this same airflow can transprt aeolian particles to the far reaches of the cave. The nature of caves is that they are vulnerable to damage but can preserve climatic records going back tens of thousands of years.
Dr Craig Barnes then spoke on "Radon in Caves" introducing us to the very recent study of this subject. Although the problem of Radon in old mines has been known for some time the extrapolation of this to the occurance and risks in caves is of limited use as they are very different physical systems. Caves are often naturally ventilated in contrast to the old tin mines of one hundred years ago and the concentrations of Radon within caves is quite low. Dr Barnes then discussed the methods employed for the measurment of Radon levels in caves followed by some discussion of the sources and patterns of variation over time.
Jill Rowling finished the evening with an presentation on "Ribbon Helictites"; a form of cave speleothem discovered by the speaker a few years ago at Jenolan Caves. Unlike normal helictites which are circular in cross section these forms are flat and ribbon like. Excellent electron micrographs and slides of these enigmatic forms were shown. There may even be another previously undescibed form, "Peripatus" like, which is currently being studied.
After the talks question time answered many of the audiences queries and some adjourned for supper with the speakers afterwards.
For further information contact either of the following:
| Anna Binnie | Michael Lake |
| Chairman | Hon. Secretary, |
| NSW Division | RSNSW |
| ANZAAS | |
| Phone: 02 9487 3488 (w) | Phone: 02 9514 1724 (w) |
| Fax: 02 9489 2348 | Fax: 02 9514 1628 |
| Email: anna@phys.uts.edu.au | Email: Mike.Lake@uts.edu.au |
This lecture was sponsored by ANZAAS (NSW Division) and The Royal Society of NSW.