Irish Roots

June 20th, 2011

John Grenham


One of the hardest things for the mind to grasp is the sheer quantity of time that surrounds us. I recently came across something in Frank Mitchell's classic Reading the Irish Landscape (Dublin, 1987) that illustrated that quantity very vividly. He is writing about chalk and its place in the geological make-up of Ireland. Chalk is white limestone formed from the compressed skeletal remains of single-celled sea-creatures just thousandths of a millimetre in diameter. Think of the hundreds of millennia of warm shallow seas over Ireland needed to build up even a small deposit of chalk. But Mitchell points out that around 100 million years ago a layer of chalk more than 100 metres deep covered the whole island. Imagine that slow, invisible snowfall of tiny skeletons and then the sheer length of time required for it to produce and then compress a 100-metre-deep deposit.

And that layer of chalk has itself now vanished almost completely - outside the extreme north-east the only evidence it ever existed is a deep pit of chalk at Ballydeenlea near Farranfore in Kerry, apparently preserved when the limestone on which it was sitting collapsed. Otherwise every trace of the layer has gone. How much weathering, over how long, was needed to scour away such massive quantities of chalk?

For any geologist this all happened yesterday. There are changes in the rocks around us that record events 500 million years ago, a billion years ago and more. The oldest surviving civilization on the planet is in China, where the culture can trace itself over at least 3,000 years. There are Chinese families with traditions that follow their ancestors over more than 60 generations. This is extraordinary to our shallow Western sense of the past, but it is not long enough for even the lightest fall of chalk.

Comments and suggestions are welcome, to irishrootsatirishtimes.com.

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