Uffington White Horse as a landslip (part 1) – 10 years on and TV

Almost exactly ten years ago I wrote a post, my first post, to stop me talking to my partner about an idea that was floating in my head. The idea was that the famed Uffington White Horse might originally have been a landslip scar, subsequently adapted into the animal shape that you now see.

A couple of friends saw the post and told me they thought it was probably rubbish. Somebody supplied a comment to tell me that the horse was, in fact, a cat. I received little other feedback. Posts, like any animal, tend to die if unloved.

Now I find myself talking about this idea on a telly programme where I am presented, rightly, as an amateur. Should I defend my idea? I honestly don’t know. It was a long time ago when I wrote the about the Uffington Horse, and the suggestion that it was a landslip was only an idea, nothing more. However, I should at least lay out the facts that mean it’s still a possibility.

The Uffington White Horse, located on the north-facing chalk escarpment of the Berkshire Downs in England, is an extremely well known ‘geoglyph’. This means it’s an image laid out or carved by people onto the Earth’s surface at such a scale that it can only be seen to represent something from afar (ideally from the air). The Uffington Horse is well known both for its simple artistic beauty and its modern aesthetic. It is perhaps one of the most famous geoglyphs in the world.

What is perhaps surprising is just how old the White Horse has turned out to be. In 1994 optically Stimulated Luminescence (OSL) dating of the oldest surfaces of the White Horse indicated an age for its creation somewhere in the British Iron Age or even Bronze Age (1380 and 600 BC – 68% confidence; 1740-210 BC – 95% confidence). This makes it extraordinary that, with all the subsequent events of British history, the carving has not simply disappeared under the grass. Instead it appears to have been maintained by local people pretty much ever since.

One of the unusual stylistic features of the White Horse is that, apart from the head, it can be described as a series of arcs, all (except one, it’s ‘knee’) curving in the same direction, giving the appearance of leaping, the typical arc traced by a leaping animal. Perhaps it’s this that gives it such dynamism.

The unusual location of the Uffington Horse at the top of an almost 40° angle scarp, coupled with the way that these arcs curved with the scarp, was the reason why I first came up with the idea of the Horse being first formed as a landslip.

What is a landslip?

Landslips are simply collapses of sediment or rock, under the influence of gravity, down a slope. They come in a number of different forms, but for our purposes there are two that are relevant (both from Engineering Geologist David J. Varnes’ 1958/1978 classic scheme): translational and rotational slides. These slides tend to form ‘spoon-shaped’ scars on a slope, as if a spoon had gouged the surface of the slope away.

1) Translational slide

A translational slide occurs when the sediments and soil overlying the rocks on a slope lose their friction resistance and simply slide down a slope. At the top of the slide the soil extends and cracks apart, leaving a main scarp at its upper end where the soil is exposed in cross-section. At its base it forms a compressed mass of crumpled up sediment.

2) Rotational slide

A rotational slide (or ‘slump’) is similar to a translational slide in that the upper reaches of the failure are cracked open and extended, and the base crumpled and folded. However, in this case the failure surface at the base is generally deeper, sometimes cutting into the rock below the soil due to the weakness of the rock. This means that the main scarp can expose fresh rock surfaces below the soil. Notably, because of the rotation of the soil and rock in the slide (hence the name), layering within a rotational slide is often tilted back up the slope.

Picturing the Uffington Horse as a Landslip

The Uffington White Horse is located at the top of a large chalk valley called ‘The Manger’. We can imagine roughly spoon-shaped pieces of earth slipping down the slope of this valley to create a scar at the top, exposing either soil or the chalky rock below which might look like a horse.

The following sequence of diagrams should give a hint of what I’m suggesting:

The first map is of the Uffington White Horse, showing its location at the top of a steep valley called The Manger. Contours are based on Ordnance Survey mapping and the work of the Oxford Archaeology Unit. Darker shading indicates areas of steeper slope which form The Manger’s valley sides. Note how the horse straddles the change in slope at the top of the valley.

The second map imagines a series of ‘spoon-shaped’ (in the broadest sense) failures as part of a complex landslip. The failure planes, which have yet to be moved here, start at or just above the valley head, and will slide down slope in the direction of the arrows (for anybody seeing the telly program you’ll recognise the basic idea in the pieces of paper I was trying to stop blowing away with Blu Tack).

The third map imagines what would be seen after the material above the failure plane has moved by a couple of metres down the slope, exposing either fresh soil or chalk at the extended upper part of the failure. The base of the failure would be a zone of compression and far less tidy than what is shown.

Now of course I’ve chosen the landslip shapes here in order to reveal a pattern looking a bit like the Uffington Horse. Other shapes would not have produced this pattern. However, these shapes are possible for landslips, and it shows how it is possible to create a pattern recognisably similar to the White Horse simply by using a landslip such as the one shown here.

Whether a landslip like this on a chalk scarp is likely is the subject of the next post (which is here).

References

Miles D. et al. 2003 Chapter 5: The White Horse, In: “Uffington White Horse and Its Landscape: Investigations at White Horse Hill, Uffington, 1989–95, and Tower Hill, Ashbury, 1993–4” (Miles, D. et al. eds.), Oxford Archaeological Unit, p61-78.

Source of the OSL dates and of the contours just around the Uffington White Horse (NB this book is now very expensive to get your hands on, but if you’re lucky a library might have it (thanks, Mark) and it contains the complete volume on a CD too).

Varnes, D.J. 1978 Slope Movement Types and Processes, In: Schuster R.L. & Krizek R.J. (eds.) Landslides: analysis and control (National Research Council Transportation Research Board), Nat. Acad. Sci., p11-33.

The basis for the recognised engineering classification of landslips.