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Old Rocks

3 May 2018

At https://phys.org/print444379905.html … why parts of earth have hardly changed over the last 3 billion years. This title refers to ancient rocks in the western deserts of Australia (and elsewhere). Geologists are not agreed on what the earth was like prior to the formation of the plates (as in plate tectonic theory). Research published in the journal Geology (April 2018) claims earth was highly volcanically active and the evidence of a violent transition to plate tectonics (or a fractured crust) can still be seen on the surface today. We learn that geology is built on the idea of uniformitarianism that is the study of geological processes occurring today in order to interpret the rocks of the past – which claims to show how the earth works over long time scales. This method breaks down when we try to understand the early earth because it was hotter and behaved in a different way. Geologists therefore have to imagine how the oldest continents formed – as no such processes occur in the modern world.

Earth is compared to Io, a moon of Jupiter, with endless eruptions of volcanoes. Hence, we have a projection (that is then modelled) as it is assumed the same thing was occurring on earth (endless volcanoes). This explains the statement above that earth was volcanically extremely active. Earth has been extremely active on other occasions (but this is not mentioned) – for example at major and lesser extinction events. How long was the earth actively volcanic during the early earth is another question altogether.

The article goes on to say there are actually parts of the continental crust that display evidence of surviving intact from the early period – old continental crust (or rocks). This has been a perennial problem for geologists faithful to the plate tectonics paradigm. It is thought most of the world's crust has been melted, uplifted, swallowed by the mantle, and eroded over long periods of time – but some regions have not changed. At all. In billions of years. These are flat land forms found in western Australia, the Amazon Basin, southern Africa, and parts of Canada. Plate tectonics, we are led to believe, creates mountains – and these eventually erode away. Therefore, why do old pieces of continental crust not do the same? Why aren't they covered and out of sight, smothered in later sedimentary layers? They have a theory of course – but see what you think.

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