Some would more readily claim it’s the colour of chocolate, but our cub reporter Angus Young is rather more prosaic than poetic.
In my early days as a cub reporter (last week, then? ed) in East Yorkshire I would go out on assignments with a veteran Scottish photographer called Rab McKenzie. One day as we drove through the countryside, Rab gestured at the surrounding landscape. “See all that?” he said with a flourish. “It’s all glacial shit!”
At the time, I didn’t have Rab down as a geology expert and I wasn’t expecting a lesson on the subject but, of course, he was right. Beneath us was a 20-metre thick layer of boulder clay stretching all the way to the coast having been deposited by melting glaciers during the Ice Age. Best viewed on a visit to the crumbling cliffs of Holderness, this chunky slab of mud contains gravel, sand, stones and the occasional well-preserved fossil and derives its colour from some of the minerals within it, notably iron oxide.
The sediment created by North Sea tides crashing into the cliffs washes down the coast, sweeps around Spurn Point and ends up in the Humber to create what we can see today – an expanse of gravy-coloured muddy water sat on a bed of sticky clay rather than Barbados-style blue.
Despite their appearance at low tide, the mudbanks of the Humber – and the River Hull for that matter – are constantly changing. Each tide carries over 1,500 tonnes of sediment with it. Overall, it’s estimated that up to 1.2 million tonnes of sediment may be present in the estuary at any one time. Today, they provide rich feeding grounds for birds with the Humber now supports an internationally important number of breeding bittern, marsh harrier, avocet and little tern.
Historically, this readily accessible supply of clay also helped establish brick-making as one of the region’s earliest industries. Approximately five million bricks were used to build Hull’s town walls which were said to be the largest brick-built construction in the country in medieval times. Similarly, Hull Minister lays claim to being one of the earliest examples of a largely brick-built church in England and was originally constructed on a raft of oak logs because of Hull’s notoriously sponge-like ground conditions.
Rab’s rather fruity description of Ice Age debris would have probably been appreciated by the founder members of the Hull Geological Society who quickly formed their own Boulder Committee. Between 1894 and 1905, committee members embarked on regular field trips to record the locations of thousands of so-called “erratic” glacial boulders left scattered across East Yorkshire by melting glaciers. Reports were made to meetings of the British Association for the Advancement of Science and other regional boulder committees set up by nearby societies. In each case, the type and age of each rock was identified in an attempt to retrace the paths of the glaciers as they changed the landscape around them.
Hull has no natural outcrops of rock. Instead, the nearest solid exposed rock is chalk which is best seen on the Yorkshire Wolds and, in particular, at Flamborough Head. The clear water in the Gypsey Race, Europe’s most northerly chalk stream running from Wharram-le-Street to Bridlington, provides a striking contrast to the brown stuff flowing further south.