Travelling back to that ancient period around 350 million years ago when these reefs were relatively new, it is not hard to imagine prehistoric fish of bright tropical colours swimming through here in a warm sea of crystal blue waters. Perhaps the arch was part-exposed by the tide for some of the day, with waves crashing and surging through. Stand inside and feel its sides, worn by the passage of 350 million-year-old currents.
A little further down the ridge, you will come across a small cave, (you may have already spotted it from the hilltop); just as with this arch, the cave at once reminds me of a scene on a rocky seashore.
Slowly but surely, our reef knolls would, in fact, have become shoreline features. As the climate became drier, the sea level dropped and this region became land-locked. By the Triassic period, around 250 million years ago, it is reckoned that these two hills would have looked pretty much as they do today. Another leap of the imagination; picture early dinosaurs grazing and hunting around a dry forest, perhaps using these knolls as hiding places, or as cover for an ambush.
But 250 million years is a long, long time ago – just how could these outstanding features, tough as they are, have been so very well preserved? Take a peek down into the narrow valley to the north side. Do you see signs of activity from a present day wild animals? Those holes and excavations you can see are a huge badger sett.
After our early dinosaurs had moved on, this area became inundated once again with shallow, muddy water, and layer upon layer of soft clay deposits built up to form shale, burying and preserving the reef for millions of years and until relatively recently.
By ’recent’, in geological terms, we mean approximately ten thousand years ago, when a huge volume of ice powered through here, scooping and scouring away the softer shale rocks, to reveal the hard limestone hills in all their glory. On the valley floor, the glacier and its meltwater deposited thin layers of this eroded material – the softer, sandy and gravelly stuff those badgers have been digging in.
Next, continue down the spine of Chrome Hill, by whichever way seems easiest, you eventually leave the open access area, so keep to the well-marked concessionary footpath. The path takes a right-angled turn to the right, up a steep grassy slope. The next stop is about halfway up and to the left of the path.
This trail was originally developed by Simon Corble for the Royal Geographical Society’s Discovering Britain.
Simon Corble is a theatre director, playwright and actor based in Derbyshire’s Peak District, is passionate about the countryside and discovering the hidden secrets of the natural world.