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On the hill at Swindon Old Town you are, geographically speaking, standing on a bit of an anomaly...

Swindon Old Town: A Geological Newcomer

Old Town's hill, compared to its surroundings, is a bit of a newcomer to the area. Sticking up 120' above its surroundings it's a dollop of younger Jurassic rock surrounded by a sea of older clay.

This young Jurassic Rock, known as Portland Rock, was created 150 million years ago in a warm sub-tropical sea and over millions of years has stubbornly refused to be eroded away.

Certain layers in Swindon's Portland Stone can be traced all the way down to Dorset.

Pretty much everywhere in the area was covered in Portland beds but at the end of the Jurassic period everything started to shift and lift.

The Portland beds were tilted up to the south and Southeast, along with all the other beds, and were folded. Then, over a period of 30 million or so years, the plug was pulled on the Jurassic Seas and the sea withdrew completely leaving dry land.

The younger Jurassic rocks, like the Portland Stone, were exposed and eroded away completely. Only in a few places like Old Town have lumps of these rocks been left behind.

Known, as an outlier Portland Stone doesn't crop up too much in Wiltshire. The only other places you'll see it are in the Vale of Wardour and the Vale of Pewsey.

Named after Portland in Dorset certain layers in Swindon's Portland Stone can literally be traced all the way down to Dorset.

Swindon's Geology Bags GWR

Looking down Victoria Road into Swindon you are standing on the growth point of pre-Victorian Swindon.

Victoria Road built in 1875 linked up what was than Swindon Old Town with Swindon's New Town. The New Town emerged with the arrival of the Great Western Railway's locomotive repair depot.

The Great Western Railway's locomotive repair depot

The depot, the nineteenth century equivalent of the Kennedy Space Centre, was the largest industrial complex in the world serving the Great Western Railway.

The arrival of the GWR literally put Swindon on the map and Swindon has its geology to thank for that.

GWR needed a stop over, between Bristol and London, to site its locomotive repair depot and to swap out engines. Although Swindon wasn't the half-way point its location in a flat valley was an ideal place to swap out engines before the long haul up the hill to Box and Bath.

...cross over Victoria Road, at the zebra crossing, and head down Union Street to Christ Church