Extract from What a Wonderful World: One Man’s Attempt to Explain the Big Stuff
As I recently mentioned, I’m hosting a stop on Marcus Chown’s blog tour to promote his outstanding new book. This is going on for two weeks, so if this interests you, do head along to see the other great things that are going on elsewhere.
I found myself in an awful bind over this. I wanted to run an extract of the book, but I was spoilt for choice in picking one. Every conceivable subject was covered with care and wit, providing a surprising amount of detail for such a huge range of topics. In the end, though, I went for the opening of the section on geology, introducing the subject with a general overview before moving on to cover the details of plate tectonics, as the explanation of why Young-Earth Creationists are wrong seems to fit so well with my typical subject matter.
I hope you enjoy it.
The world has not always been the way it is. This is one of the most powerful and revolutionary insights in history. It spawned a new science – geology – and it inspired Charles Darwin to recognise that all creatures on Earth have diverged from a common ancient ancestor.
The evidence that the Earth is not static – that it was not made in its current form by a Creator – is subtle. For instance, on Madeira, a volcanic island off the north-west coast of Africa, fossil seashells are commonly found more than 6,000 feet up on the summit of the tallest mountain. How did they get there? The obvious but mind-blowing answer is that the mountain began its life beneath the sea and rose skyward.
Mountains do not rise by a noticeable amount in a human lifetime. Consequently, it must have taken a huge number of human lifetimes for Madeira’s tallest mountain to have risen from beneath the sea to a height of more than 6,000 feet.
‘A huge number of human lifetimes’ is not exactly precise. Fortunately, other subtle evidence exists that can provide the precision. Scientists in the eighteenth century could see mud accumulating at the bottom of lakes, deposited there by the rivers and streams. They could also see cliffs and other exposed rocks that looked remarkably like mud, piled thin layer upon thin layer.
The suspicion grew in their minds that the rocks had been made by mud settling to the bottom of an ancient body of water. Such a process was extremely slow – in a century, it would deposit no more than a fraction of an inch of mud. The unavoidable conclusion was therefore that the rocks must be hundreds of millions of years old – created over millions of human generations.
For the ﬁrst time in history humans contemplated Deep Time, compared with which their existence was as transient as that of a ﬁreﬂy in the night. The Earth is not just old, it is beyond-human-comprehension old. ‘There is no vestige of a beginning, no prospect of an end,’ said Scottish scientist James Hutton in 1788.
Today, we know from the radioactive dating of meteorites, the builders’ rubble left over from the formation the Solar System, that the Earth is about 4.55 billion years old – that is 4.55 thousand million years.
Mud becomes mudstone after it is deposited on the bed of a body of water, then compressed by the layers of mud deposited on top. The creation of such sedimentary rock illustrates another profound insight.
The past, contrary to novelist L. P. Hartley’s famous opening sentence, is not a foreign country; they do not do things differently there.
The processes that have changed the Earth’s surface are nothing more than the processes that are going on today – weathering, volcanic eruptions, and erosion by water and wind. Working away over mind-cringing spans of time, they can literally move mountains – or grind them into microscopic dust.
Two mountain ranges that illustrate this are the Himalayas, which today are rising skyward, and the Caledonian mountains of Scotland, the eroded stumps of a Himalaya-like chain born about 500 million years ago. Both ranges have been created by an identical process – the titanic collision of giant chunks of the Earth’s crust. The evidence for this can be seen in both locations earth works in the form of huge folds created by layers of colliding strata rucking up over each other.
The fact that chunks of the crust can collide like this leads to another revolutionary insight. Although the early geologists believed that the surface of the Earth merely moved up and down, creating features such as mountains, in fact, the surface also moves sideways.
© Marcus Chown, extracted from What A Wonderful World: One Man’s Attempt to Understand the Big Stuff (Faber, October 2013, hardback £17.99)