When the Geological Society was formed in 1807, there was no geological profession, and so people like economist David Ricardo could be founding members.
Since that time, geology has become both a science and a profession, but like some parts of biology, it still leaves room for amateurs to contribute something.
This file is http://members.ozemail.com.au/~macinnis/scifun/splatsearth.htm, first created on February 16, 2008. Last recorded revision (well I get lazy and forget sometimes!) was on February 16, 2008.