Digging the Dirt – an experiment in alfresco sieving!

Paul Ensom
Collections Leader
Department of Palaeontology
Natural History Museum
London

This 'hands on' experiment aimed to show that with a relatively small expenditure, and a little bit of preparation (not essential – but see 'What works?' below), one can involve people in a practical aspect of geology, enabling them to experience discovery at first hand, to get their hands dirty, and – you never know – maybe discover something remarkable in the process. An experiment this most certainly was as I had never tried this with a group of people before. Participants were provided with an inexpensive plastic tea strainer, a small sample of pre-soaked sediment, and a plastic 'fruit-salad' bowl as used for parties and which holds sufficient water for the sieving to be done. Those adventurous enough to partake soon got the hang of the sieving process and 'clean' residues were soon being tipped onto plastic lids to sort through.

What works?

This question can be answered at two levels. Firstly what works in the context of reaching out to the public, and secondly, what will work at a purely practical level.

1. On the first level of getting the public involved, people need to have their curiosity aroused. I was encouraged when one or two members of the public, outside the intended audience, who happened to walk by as I was setting up the demonstration, were sufficiently intrigued that they found themselves enjoying getting their hands dirty for the sake of science. Natural curiosity tends to override any inhibitions, and then it is down to the 'leader' to encourage and guide. The reaction of members of the workshop who became involved was equally encouraging.
2. If your initially enthusiastic audience goes on to have a bad experience on their first attempt at small-scale sieving, they may never wish to get involved in such an activity again! Making sure that it will work for them first time round is important. Building on initial success, one can go on to demonstrate that ending up with an unyielding ball of clay rolling around your sieve is very frustrating, messy and not very productive! Preplan and select a sample which you know is going to breakdown in water and which contains recognizable fossilised remains. If necessary carry a dry and productive sample with you as an insurance policy. Costs of the sieves, etc., could be factored into any charge made for the field trip or Jurassic Coast Walk.

What doesn't work?

As noted above, sediments that will not breakdown in water, or which having done so immediately flocculate when an attempt is made at sieving them are not good for morale. Strong winds complicate matters by blowing light-weight pots over/away. The smallest specimens retained by the sieve mesh may be too small to easily view with the naked eye and wet residues are generally more difficult to sort than dry ones.

What could we do better?

The answer to some extent depends on where you are. A field centre may allow the provision of permanent facilities sheltered from the elements and with the benefits of running water, working tops and maybe even a binocular microscope or two. In such a situation, samples can be prepared in advance. Literature and wall charts may be made available illustrating what might be found. A supply of specimen tubes may be required to store treasured finds in.

A field-based experiment is much more challenging and you have to make do with rather more primitive facilities! Sample choice will be driven by practical considerations – what will break down in water very quickly! Access to hand lenses is useful. Identification sheets of photographs or drawings could certainly be provided to encourage participants to identify the fossils they find, and if the sheets are laminated they will survive regular bouts of mud, wind and rain!