The Clifton Suspension Bridge and Avon Gorge

Here's the third blogpost about my journey to Bristol, which I felt I'd find more words on than the other four places, as well as it being an opportunity to mention someting slightly science related (as in why certain rocks have the colours that they do).

So before I went to Ashton Gate to watch Millwall play, I went to the Clifton Suspension Bridge which spans over the River Avon, near the outskirts of the city. And it's a true marvel, if not a bit unsettling if you have a fear of heights (as I do). You're seventy-five metres above sea level, with the Avon next to a busy road and a series of rocky cliffs - but thankfully there's a large fence that stands around part of the bridge, which were installed due to the bridge sadly being known as a place where many have committed suicide.

Without the bridge, it would be harder for Bristolians to access the large fields and golf courses on the other side, and likewise for those wanting to go to Bristol from towns like Portishead and Nailsea. The bridge is part of the B3129, after all, and tens of thousands of cars travel this way daily (in 2010, at least). It's been like that for over two hundred years, ever since Isambard Kingdom Brunel designed the bridge and oversaw his construction. Unsurprisingly, since the bridge is so impressive, he has two plaques in his honour next to the bridge. It took nearly thirty-three years to complete, but Brunel never saw through to the end of the project as a result of disruption caused by the 1831 Bristol riots, a project which spanned over half his life. Indeed, plans to build such a bridge were even older than Brunel, with the first plans drawn up in 1754.

If you visit the bridge, you could do so by car, provided you remember to pay the £1 toll to pass through (unless you park nearby). The bridge has two lanes, one for each direction, with a gate controlling the flow of traffic, I assume due to the toll as well as the lanes themselves being rather narrow. Otherwise, you could walk or cycle there - it's thankfully free - but once you've chosen a side of the bridge, you have to stick to it, unless you go all the way around. You could obviously walk through the road, but there are signs against that. But maybe you're not here to just pass through - perhaps you'd rather look down and take in the sights of the Avon Gorge, if you're not looking up at the chains or towers at either end of the bridge.

To one side, you'll find a building looking a bit like a castle - that's the Clifton Observatory, which like many moden tourist attractions has a cafe, but which was once actually a snuff mill before telescopes and a camera obscura were added to allow artists to view the landscape better for their paintings. There are caves around there as well, and I could spot a stray yellow fence, seemingly some observation deck which I'd be too scared to access. 

 

 

 

 

But perhaps that sheer drop interests you instead. It's impressive how they managed to construct a bridge which spans the Avon Gorge, what with it being over 400 metres long and held together by a few, albeit very strong, chains and cables. Folklore would tell you that a giant named Vincent created this gorge, whilst many nowadays assume the gorge was formed in the aftermath of an ice age, which would explain its sheer size despite the size of the comparatively smaller river.

 

 

 

 

 

 

 

One thing which intrigued me, however, wasn't the silt-filled river itself, but rather the rocks either side of the river bank that you can see from the bridge. They're limestone, which as I've mentioned before on this blog is a form of calcium carbonate, which explains their white-grey colour, since some of the limestone may be impure. It's important to note however that the rock of the gorge is composed of separate parts, some of which are much softer than others, and even the limestone can sometimes also be oolitic (ooids are small CaCO3 grains). These rocks were especially popular to mine for nearly two hundred years, where quarries were set up to mine the limestone as well as other elements like lead and iron, but the area itself has been an SSSI since 1952, and the area hadn't been mined many years before that. You could always go and visit the area beyond the bridge, but I didn't, so there's not much else for me to add.

But the gorge is also covered by a series of forests, with some parts belonging to parks such as the Leigh Woods - protected by the National Trust - whereas others are parts of various estates. I could go into detail on the forests and the wildlife that inhabit them, in fact there was a display next to one of the Brunel plaques on the wildlife in the area, but I didn't go to see them. I had a match to go to, after all, but rest assured the place itself is beautiful and no words would be more effective than seeing the place in person.

Aside - When I was looking at the gorge, I started to wonder as to why certain cliffs come off as different colours, and it's unsurprisingly due to the different elements and compounds present in the cliff, as well as fossilised deposits - the Grand Canyon, for instance, is rather orange in certain parts due to the presence of rust. The White Cliffs of Dover are another good example, as they're not entirely white as a result occasional flint which is actually the remnants of organisms like sea sponges. And that's not forgetting about the various greens which can be found on cliffs, which are a result of plants like moss which naturally grow over time (and which can also be found on many older buildings). But that's going completely off track - I was merely curious - and this is probably a blogpost for another time.)