Geological Time SpiralPosted: January 15, 2015
The time spiral – The spiral represents the evolving Earth over 4,500 million years. The rocks of the Jurassic Coast World Heritage Site cover the whole of the Mesozoic Era – the whole of the reptiles, dinosaurs and mammals. Illustration by David Scammel. (Taken from the book The Jurassic Coast: An Aerial View through time, Coastal Publishing, 2011)
I have been looking into the geological history of the earth to learn more about the way that geologists have plotted the earth’s history. Rocks are a great mystery to many because of their continued existence, far beyond our own.
Geological history has been plotted by geologists as a way of interpreting and understanding the world’s roots. It is expressed in a four tiered system called the geologic time scale (GTS). This contains eon’s which are made of era’s that are broken down into period’s, that are then sub-divided into epoch’s. Each sub-division enables a more in depth look at the geological history of that period. The illustration shows a simpler version of this with just the Era’s and Periods.
Leonardo Da Vinchi was one of the first to spot curious clues that indicated the date of rocks. In one of his many notebooks he questioned: Why do we find the bones of great fishes and oysters and corals and various other shells and sea-snail on the high summits of mountains by the sea, just as we find them in low seas? The Notebooks of Leonardo Da Vinci, Vol II (Jean Paul Richter, ed.), Dover Publications, Inc.: New York, 1975, p. 217 taken from http://staff.concord.org/~btinker/GL/web/geology/english/dating_rocks.htm
Leonardo seemed to grasp what became known as the ‘law of superposition’.
Other ways to date rocks:
- faunal succession – looking at the fossil content
- ‘radiocarbon dating’ which was invented in 1960. This examines a chemical process of the nuclear decay of radioactive isotopes in the rock. This process is able to give an absolute dating of rocks.
It was interesting to research into the science of geology. The GTS is something I was aware of but never fully took the time to grasp however now I feel that I know more about the make up of rocks. Although some of the mystery is taken away with this knowledge, the initial mystery followed by knowledge is a process that I enjoy. I am drawn to an object because I do not know much about it and then I want to find out more.
The image above is from a book about the Jurassic Coast. This is an area on the south coast of Britain that stretches from East Devon(Exmouth) to Dorset(Swanage). The area has been given the status of a World Heritage Site because of its unique and varied geology. The coastline rapidly changes as you walk along it as this small area covers a whole geological era. The era when dinosaurs and the first mammals roamed, hence the name ‘Jurassic’ coast. Records of this past life is recorded in fossils, which are a common find in this area. It is the combination of all of these facts that makes this area so interesting to me, it is somewhere that I never get bored of visiting. I am recording rock textures for my installation and this is an area that I will no doubt visit again soon to carry on my collection.