Landscapes and Geological History – Norwood and District

Talk on 20th August at the Phoenix Centre by Dr M J Heath

Dr Heath explained that the time scale that his talk would cover would start with the supposed Big Bang and decelerate exponentially to the present time. He began his talk marking the beginning of time with the Big Bang, and that the subsequent expanding gases would coalesce under the influence of gravity to form galaxies and stars and other bodies like the Earth. The Earth suffered a calamitous impact from another body and, it is thought, this resulted in the formation of our satellite, the moon. He managed however to leap from periods billions (or trillions) of years ago to how the Earth gradually changed from being a fiery ball, devoid of habitation to the various land masses we now identify as continents. The Earth went through stages of being mainly ice and glaciers, and volcanic eruptions on a grand scale causing its crust to rise in parts, forming mountains, ridges folds and basins. The depictions of the surface of the Earth at various stages showed a very different arrangement of continents from what we know today. A very early fossilised remnant of something that looked a plant or possibly a creature of some kind, still remained a mystery, but was regarded as the earliest possible example of the arrival of plant life.

The talk, illustrated with many slides, went on to show the evolution from simple single cell organisms up to more complex creatures such as insects, reptiles, amphibians, and finally warm-blooded animals and birds. Many of these theories were supported by the evidence of various fossils and other remains.

Geological history was explained in well-presented and interesting detail, with maps showing how the development of the landscape we know today was formed. Particular examples were the basin in which the Weald is situated, and the land ‘folding’ that created the North and South Downs, with evidence showing that it was once under water. The rivers of course had to find their way downhill to the sea in the folds between areas of higher ground, and until Britain was finally detached from Europe the Thames would have found its way to the North Sea. London was on a bed of clay on top of gravel, and at one time water flow could well have reached the sea in several separate rivers.

Dr Heath provided an account of how knowledge of the formation of the Earth was acquired through analysis of types of rock. He explained that chalk, a major component of South-East England’s geological make-up, was not a rock but an agglomeration of tiny creatures as small as a grain of sand. A picture was shown of a fragment of meteorite which struck the Earth at the turn of the century. Another showed the gravel and stony remains of previous water movements from ground near the surface of a site, currently at the top of our 450 foot high hill, not 50 yards away from the Phoenix Centre.

Turning to another local issue Dr Heath explained that by using solely a contour map he could identify the course of the Effra River correctly. It would of course have had tributaries, but the course was not always that set out in guide books. It certainly produced a substantial flow of water, and one story he told was of a coffin (supposedly washed out from Norwood Cemetery) was once carried along it into the Thames in the nineteenth century.

An account was then given of the progress made in creating wild-life habitats in the Dulwich and other areas, and the increase in the numbers and varieties of butterflies and dragonflies – informed members of the audience vied with each other in identifying them.

Dr Heath outlined the support from some local authorities to create natural habitats for local life and hoped that those present would do their best to promote other wild-life habitats and the trees and shrubs that would support them. Questions were then invited and discussed.

David Khan

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https://www.norwoodsociety.co.uk/

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