James Hutton’s revolutionary idea that our landscape was formed over an enormous period was effectively the beginning of geology as a science.
James Hutton’s revolutionary idea that our landscape was formed over an enormous period was effectively the beginning of geology as a science.
It was controversial too – outraging a society which believed that the Bible held proof of the Earth being created no more than 6,000 years earlier.
In the 1650s, an Irish archbishop named James Ussher (1581–1656) attempted to work out the date of ‘creation’ as described in the Bible.
He traced the lineage of Biblical characters, consulted historical documents and arrived at an exact date: 23rd October 4004 BC. This result was widely publicised and many people accepted it without question.
But around that time lived Danish scientist Nicolaus Steno (Danish name Niels Stenson, 1638–1686), one of the first people to take a scientific approach to geology.
Steno suggested that layers, or strata, of rocks are laid down one after the other – so the oldest ones are at the bottom.
By differentiating between layers, Steno divided Earth’s history into different phases, or eras. This remains a major feature of modern geology.
The following century, two opposing schools of thought arose to explain the rock formations.
One suggested they were all laid down over a short period, in a worldwide ocean.
The other, pioneered by Hutton (1726–1797), argued that the landscape was shaped gradually over a very long time by processes that are still ongoing. In other words, Hutton said, rocks are still being formed – a revolutionary idea at the time.
Hutton suggested that the centre of the Earth is very hot and that some rocks that are solid now were once molten (igneous rocks).
He also claimed the heat from Earth’s core drives mountain-building and volcanoes.
These ideas were almost impossible for his contemporaries in the 1780s to believe.
It was the 1820s before they were generally accepted.
Since then, geology has matured into a truly modern science.
One of the most important new theories was plate tectonics, developed in the 1960s.
This suggests that the Earth’s crust is made up of fragments called ‘plates’, moving around on an ocean of molten rock (lava).
Where plates collide, the crust ruffles up, earthquakes are common and mountains form.
At the boundary between plates that are moving apart, lava can leak out, forming brand new rock.
The evidence for this theory is overwhelming and the boundaries between the crust’s plates are well known.