Saturday, 27 February 2016

The big glacier

One reason why Paxton Pits Nature Reserve is so popular is that it is very close to the A1, the major road that runs from London to Edinburgh. I drive on it every day, and I'm not very fond of it.

Just as I turn off to come into Little Paxton village I briefly join a much older road, that is called The Great North Road. If I park at the Nature Reserve it is only a short walk to the Ouse Valley Way where I can watch the boat traffic on the river or look beyond to the East Coast Mainline. All of these routes (the A1, The Great North Road, the Ouse Valley Way, the Great Ouse and the railway) all occupy the eastern side of the same valley. On the ridge above there is another parallel road that goes from St Neots through Great Paxton and the Offords to Godmanchester before joining the Great North Road in Huntingdon. This is just a stretch of the Roman road that they call Ermine Street.

We know that the Romans built Ermine Street to get from London to their northern outposts beyond York to Hadrian's Wall. But, did they really?

When we ask, "What did the Romans ever do for us?" We say "Roads!" like there were no roads here before they came. The Celts had horses and chariots and so we must assume they had roads as well. Recent excavations near Peterborough have unearthed a lots of interesting objects, including a complete chariot wheel, just in the last few weeks. Now, this wheel was from the late Bronze Age, maybe a thousand years before the Romans came.

I used to suppose that pre-Roman, Celtic Britain was fragmented into tribal areas so there would have been no through-routes, but this is nonsense really. We know that there was a lot of trade going on in pre-Roman Britain, both internally and internationally, so I find it hard to believe that there were no long-distance routes before the Romans came. In fact, I think that the Romans may have simply improved existing routes.

If you were in charge of a conquering army and you wanted to plan a new route from south to north you might just draw a straight line on a map and go for it, but it's more likely that you would use existing routes and look at the topography for alternatives.  I would also want to make sure that the local resistance didn't have the use of any alternative routes.

So, our north-south route is very, very old. Why did it take the precise route it did, and why do we still use most of the route today?

The big factor influencing North-South routes is glaciation.

When I went to school, I was taught that the glaciers never came south of the Wash in the east, or the Bristol Channel in the west. It turns out that they did and that their icy grip influenced the climate and the landscape right down to the south coast.

Roughly 450 thousand years ago we went through an extremely cold spell and a glacier pushed its way south from the Wash, almost to London. It carved away the soft chalks and greensands to reveal the Jurassic clays beneath, unearthing fossils of ichthyosaurs, belemnites and ammonites and leaving piles of flints behind. The rivers Great Ouse, Ivel and Purwell were diverted into the resulting valley (which is far too big for the rivers that are there now) creating a level route for future settlers.

The Flying Scotsman in the Great Ouse valley
route today. By Kevin Gipp
That explains why the Celts and the Romans used the route but, like everything in life, it's not that simple. The river valleys have always been prone to flooding so you always needed an alternative route on higher ground. The result was that there was always a low road and a high road.

When toll roads were introduced, people found ingenious ways to bypass them by creating a network of drove roads, often along lost, ancient highways. And so it was in my village where geese and sheep were herded along a lane to a watering hole, the village pond, which became a muddy eye-sore. It is now totally filled in.

Next time you take the train to London, keep an eye on the landscape as you go south through Sandy, Biggleswade, Arlesey and Stevenage and remember that you are following a glacier. After Stevenage it gets a bit hilly, so you can tell that the big glacier petered out around there.

I find all of this fascinating, and I hope you do too. If you are interested in wildlife you will not be surprised that it was not only people who used the glacial route northwards; flowers and insects populated England along the same route.

The big glacier wasn't the last one to reach us, but it was the biggest. I'll tell you about that another time.