The Beginnings Of An Old Earth Model

There have been many attempts to date the age of the Earth. At one extreme Aristotle believed that it was of infinite age, whereas at the other, the modern day young earth creationists claim the earth to be only a few thousand years old. Probably the most famous estimate being that of Bishop James Ussher, who not only came up with a number of years, but also the day and time of “creation”: Sunday 23 October 4004 BCE; just after tea time. He reached this figure by adding up the genealogies of the bible. I have always wondered how he managed to reach that figure as the genealogies of Jesus (found in Matthew 1 and Luke 3) are irreconcilably contradictory, with Luke also adding an additional 15 generations.
A major problem here though, is that it assumes the bible must be true. If the bible is not true, then the foundation of that figure is swept away in a flood of biblical proportions. Proper independent means show this age to be laughably false. Current estimates are that the earth is around 4.5 billion years old. This means that the creationists are out by a mere 4 499 993 996 years. The order of magnitude of this error is equivalent to thinking the distance from New York to Los Angeles is only 28 feet.

James Hutton was one of the first to realise that it takes a long time to erode mountains and form new rocks. Perhaps one of his most significant discoveries was the angular unconformity at Siccar point on the Berwickshire coast. An unconformity is a junction between rock depositions that has a significant temporal gap between the layers. An angular unconformity is one where the underlying (older) rocks are tilted at an angle and overlaid with younger more horizontal sediments. In the case of Siccar point, the older Silurian rocks (boxed in red in figure 1a) have been turned on their side by massive tectonic movements. This formed a mountain range as the ancient Iapetus ocean closed, resulting in Scotland and England joining together.

Figure 1a

Older upturned rocks in foreground and on right. Near horizontal younger rocks in distance and on left. In both cases, erosion has exposed the beding planes.

As the Silurian mountains near Siccar eroded and formed the younger Devonian sandstones (boxed in blue above) that now lie on top of the upturned older strata (chunks of the older Silurian rocks can still be seen in the sandstone matrix (See Figure 2)). Hutton reasoned that this would take more than a few thousand years and this work began to challenge the authority of the bible and earned Hutton the title of “father of geology”.

Figure 2

Sediments on the floor of the Iapetus ocean become rocks. These are buckled and turned on their sides as the ocean close, forming fold mountains. These mountains erode and become covered in younger sediments, forming the unconformity.