A ride down memory lane

This feature was inspired by Brian Turnbull, who recently led a ride to Preston Park. It was a short ride, a bit tame for some of the 14 riders so Brian tried to make it more interesting by calling it a "Bespoke ride" and linking it to the Cleveland Dyke. None of the riders knew anything about Quarry Woods or the outcrops near Great Ayton. Brian remembered an article (inspired by an extract from cyclists 1943 diaries) in the Autumn 2011 edition of 'Fixed and Free' and was able to use this information during the ride to enlighten clubmates about these significant local features. This article is reproduced below.

Fixed & Free Autumn 2011 

The Cleveland Dyke

Brian Turnbull

 No, it’s not someone you might meet in downtown Middlesborough late at night, but an important and unique geological feature found in our area. 

If you cycle on the B1292 road from Tree Bridge Farm towards Great Ayton, travelling north-east towards Roseberry Topping, glance to your left to see a distinct ridge, which runs in the same direction. At this point it looks like an elongated giant Cornish Pasty that stretches in a perfectly straight line from Quarry Hill opposite Nunthorpe Hall to Cliff Rigg Quarry just south of Roseberry Topping. You really can’t miss it. It’s right under your nose, or rather right under your feet. 

Most of our area is formed by sedimentary rocks which were laid down in horizontal layers about 200 millions of years ago, but The Cleveland Dyke is different. It is a volcanic rock “only” about 30 million years old, which has cut through the layers of sedimentary deposits to form a vertical wall of harder rock. This is a valuable material, which has been quarried to produce cobble stones and road building materials. It is a Dolerite similar to the Whin Sill at High Force, and is known locally as “Whinstone”. Examples can be seen in many parts of Cleveland in the form of cobbles or path edgings. 

The story began almost 300 miles away on The Isle of Mull, which was the site of a tremendous volcanic eruption. It was probably bigger than Krakatoa, and the magmatic force was so powerful that the earth’s crust was split open and cracks radiated away from the epicentre. 

These cracks formed incredibly straight lines, like spokes in a bikewheel and one such crack split the existing strata across southern Scotland, Northern England, and through our area. It only disappears just west of Ravenscar. The cracks were filled with molten igneous rock, which cooled to form a vertical wall within the older, softer layers. The dyke varies between 20 and 60 feet wide. Its depth is immeasurable. 

Exposures of The Dyke can be found at Quarry Wood in Preston Park, The Blue Lagoon above Gribdale Gate, disused quarries to the north east of Kildale, a quarry at Egton Bridge, and on the hilltop ridge just east of Goathland. 

So as you pass “Whinstone View” near Great Ayton, now a quiet little caravan site, just think; the earth beneath you was laid down in tropical seas or river deltas when dinosaurs lived hundreds of millions of years ago, then, fairly recently in geological time, the sedimentary layers were ripped apart by the most fearsome Hebridean volcanic action and a 300 mile long wall of rock was thrust into place. Maybe downtown Middlesborough is a safer place to be after all. ✳