Thursday 19th November
School of Earth Sciences Lecture Theatre,
University of Tasmania
A public lecture presented by the Geological Society of Australia (Tasmania Division):
Dr David Leaman
Some of Earth’s Secrets
Newton noted “if I have seen further it is by standing on the shoulders of giants” (1676). But, what if the giants were in error? Would we dare comment? Do we build on error? It has happened, more than once. It is easier to accept or assume, presume and criticise, than to check, resolve and revise. Others like von Bauer or Schopenhauer have noted the difficulties implicit in asking questions or suggesting change. But, unless we ask and test, geology, like every other topic, will have some feet of clay and may need new thought or approaches. We must be careful to separate presumption and interpretation from observations and direct deductions.
Speculations about Earth’s and Moon’s origins disguise a reality: we have no real idea, but it is possible to rejig a few of the assumptions currently made. We know much about Earth’s shape but have no perfect explanation for its cause. Likewise, we have accepted an age for the planet. But is it only a minimum, or even irrelevant? Our ideas about the inner Earth were shaped by Greek notions and the physics of the early 19th century. Assumptions regarding it may need a major shake-up. The content of the core is one of Earth’s greatest secrets. And, just how does Life tie into all this? Many concepts in tectonics must also be challenged for physical validity, and possible solutions then not denied on the basis of lack of currently explanatory theory.
An overview of what we do reasonably know, or could know, describes an ever-changing, dynamic, vibrant planet. This means that the present is not necessarily a simple key to the past; the geologist needs to juggle implications and processes. This thought, on its own, demolishes those philosophies which claim “Earth was made for us”, or that we can sustain modern factors as applicable in the past.
This lecture is a declaration of issues, for the secrets remain secrets. It is up to us to take them on, if we can but see them in a different light.
David Leaman is a graduate of the University of Tasmania from the days of the world-renowned Prof. Sam W Carey. At the Geological Survey of Tasmania he was a mapper, engineering and groundwater geologist and specialist geophysicist, before leaving to establish a consultancy in 1981. He has worked on many mineral, engineering and petroleum exploration projects in the Australasian region. Between 1972 and 2001 he was also a part-time lecturer at UTas and led many field excursions. He has always been prepared to challenge himself and others and argue heresies based on real observations. It remains his view that this is how we, singly or collectively, get corrected and advance our science. In recent years, he has written several books on geology and hydrology for a general readership. His latest, “Earthly Secrets”, forms the basis of this lecture.