High Tide Blog

Roger’s blog appears regularly in the Scarborough Review. Read his archive of posts here.

All is chalk

To Bridlington this month to give a talk to the venerable society of Augustinians. It always pays to do your research before you get up to address an audience, so I spent some time looking up the geology of Brid, in particular the effects of ice.

Around 3 million years ago the coastline south of Flamborough was quite different from today. The coast ran in a line west from Flamborough past Sewerby – as it does now – but went inland for 30 to 40 kilometres before running south to meet the Humber west of Hull. The line of the old coast shows up in an escarpment that runs in a long arc along the edge the Wolds.

In the last 3 million years 4 successive glaciations have brought huge quantities of boulder clay onto the Yorkshire coast. The bay south of Flamborough was filled with till, pushing the coastline out into the North Sea. By the time the last ice sheet melted away, around 12,000 years ago, the land of Holderness was at its furthest extent. Since then the sea has rapidly eaten away at the glacial mud, bringing the coast further and further west.

The earliest records date from Roman times when the coast was around 20 kilometres further east than today. More recently villages established along the coast have been eaten up by the sea. More than 30 named villages have disappeared from Wilsthorpe in the north to Ravenspurn in the south.

While this is worrying for coastal dwellers, it does mean that rocks and fossils are continually washed out of the mud onto the beaches of Bridlington Bay. Much of this material comes from Scandinavia and Scotland, but there are also remains of ice age animals buried in the till. Not only that, Jurassic material is washed down the coast by longshore drift, so Whitby ammonites can be picked up on the beach at Spurn head.

Coastal erosion is a fact of nature but remains a problem for some; as one Holderness local put it succinctly: ‘You rive all your life and your farm falls in the sea.’

Looking for fossils

One fine morning earlier this month I found myself on the slipway at Robin Hood’s Bay. I was there to help Will Watts of Hidden Horizons with a large school trip. Will was to take one half of the group of rockpooling for an hour, while I led a fossil hunting session, then we’d swap. So there we were at 9:30 am, marveling at the warm weather and the serene tranquility of the bay at low tide. There was hardly a better place to be in all the world.

Suddenly the calm of the bay was broken by the arrival of our party of 50 revved up 10-year-olds, all desperate to find something exciting on the beach. After a brief intro we headed south along the scar. On every fossil walk this is the most anxious and exciting bit because each walk is different. Every day the tide comes in twice and pushes the rocks and pebbles around. Occasionally it does more than that – it shifts vast quantities of sand and rock, burying some areas of the beach and exposing others; it washes debris onto the scar, rips lumps out of the cliffs and scours the beach. Going to the coast after a big storm is like entering a house after a teenage party – stuff lying everywhere with the guilty party sleeping gently just nearby.

So this could be the trip where all the fossils are buried under sand, where all the pebbles have gone, where the scar is just blank rock. Fortunately it never happens like that. Sometimes you see oodles of fossils straightaway, often it takes a few minutes for everyone to get their eye in. But then, almost miraculously, the fossils start to appear – crinoids and bivalves most commonly, then come the corals and the ammonites, the gastropods and the belemnites.

And every trip I tell myself not to worry, there will be fossils, and there always are. But a bit of nervous anticipation adds to the thrill of discovery – don’t you think?

What is the Dogger?

What is the question I get asked most often when I give talks on local geology? Any guesses? Perhaps: ‘Why are there fossil seashells on the tops of hills?’ or ‘Does fracking pollute underground water?’ or ‘Is Whitby jet only found in Whitby?’ Well, I get all these but the runaway winner is ‘What does Dogger mean, and is it the same as Dogger Bank?’

This comes up because the Dogger is a crucial marker bed along most of the Yorkshire coast – so I mention it a lot in my talks. What do I mean by ‘marker bed’? There’s no strict definition but the Dogger is a thin (from 1 to 12 metres thick) layer of very distinctive rock that marks the boundary between the Lower and Middle Jurassic strata. It is visible along the coast from just north of Runswick Bay, south as far as Saltwick.

All the dales in the North York Moors are cut through a layer of hard Middle Jurassic sand and gritstone into the soft shales of the Lower Jurassic beneath. This change shows up brilliantly in every dale from Westerdale to Glaisdale and Bilsdale to Farndale. Why? Because the Middle Jurassic rock is infertile and is therefore covered in heather moorland, while the Lower Jurassic supports pasture. And the Dogger marks the boundary, visible as a straight line between moorland and green pasture.

The Dogger is rich in iron, particularly at Rosedale where it was heavily mined on both sides of the dale. Look closely and you’ll see how the old mine workings are at the boundary between moorland and fields.

So what does Dogger mean? It seems that Dogger Bank is named after the Dutch name for a two-masted cod-fishing boat, while ‘dogger’ is a general English word for, well, a lump. So because our marker bed is full of lumps it is called the Dogger.

Museums of wonder

Here on the Yorkshire coast we are lucky to have two of the finest geological museums in the country: Whitby Museum in Pannett Park and Scarborough’s very own Rotunda. The Rotunda has been celebrating the anniversary of its re-opening in 2008 – that historic event saw the museum going back to its original purpose as a museum of geology. I was asked to give a talk about all this at the Rotunda, and it set me thinking about what museums are for, and how they have changed over the last 200 years or so.

When the Rotunda was built in 1829 museums had a clear purpose – they were to show the public the latest innovations. These were often mixed in with some objects from ancient Greece, Egypt and Rome, but this was a time of rediscovery of the classical world, so these too were at the cutting edge of knowledge. The Rotunda is a prime example, showing off William Smith’s revolutionary discovery that different rock strata each hold different groups of fossils – and that these fossils are unique identifiers of the rocks. Museums were used for research (the Rotunda had a laboratory in the basement) and science teaching.

The Great Exhibition of 1851 showed British ingenuity to the world and more and more museums continued this theme. The culmination of the heroic age of museums was the opening of the Natural History Museum in London in 1881. The building covered five acres and was built to hold samples of everything that nature could offer.

But by then museums were being overtaken by events. A plethora of discoveries showed that it was simply impossible to contain everything in one building, and gigantic museums were just exhausting for visitors. More seriously research and education moved to schools and hospitals leaving museums as dull spaces without a real purpose beyond preserving the past.

In the last 30 years or so this began to change as museum curators started to understand how to attract, entrance and amaze their visitors. The best have used the hidden riches in their collections to create great experiences for visitors. The Rotunda and Whitby Musuem are now magical places, full of objects of wonder. Go see them while you can.