Trade Secrets

[Boreades]

Horse-y islands have come up elsewhere though; are horses or horse-eared lairds, Irish or other, a particular feature of islands and/or causeways (chausee in French)? Perhaps the idea of a hybrid is appropriate for somewhere that's not quite land or sea but why horses/asses?

The sun god often rides a chariot across the heavens...... he appears he travels, he disappears into the distance, he then reappears again.

The causeway appears as the tide falls, disappears into the water as the tide rises, the reappears again. So both are metaphors for the cyclic nature of the megalithic universe.

[hvered]

Various ideas have been put forward but whatever the original purpose, one agreed fact about causeways is they're man-made constructs (though even that can prove contentious, e.g. Sark's La Coupee and the Burgh Island causeway). The material used is natural but we understand of course this is not a natural formation.

Investigating the artificiality or not of a causewayed island itself however appears to be several steps too far. If it's agreed that some if not most barrows, hills, tors and assorted cairns are 'signposts', essential for overland direction-finding, a similar signposting system at the coast doesn't seem extraordinary at all.

Looking at St Michael's Mount, it stands alone, unless you count a small rock (St Clement's) at the western entrance of Mount's Bay off Mousehole as an island. The Mount seems to comprise a rather jumbled pile of rocks, partly granite but also something called metapelite



which is clay mixed with silt and/or mud according to Wiki

Pelite (Greek pelos, clay) is an old and currently not widely used field geological term for a clayey fine-grained clastic sediment or sedimentary rock, i.e. mud or a mudstone. It is equivalent to the Latin-derived term lutite.* More commonly, metamorphic geologists currently use pelite for a metamorphosed fine-grained sedimentary rock, i.e. mudstone or siltstone, which should technically be called a metapelite

Mudstone aka metapelite is not very different from other building materials like marl, used for constructing barrows relatively close at hand such as Burrowbridge Mump and Marlborough's Merlin Mount, formations that are as big or bigger than St Michael's Mount. Geologists assume everything is natural unless it patently isn't (e.g. Silbury Hill). One cannot help suspecting that if faced with something ambiguous or anomalous, a geologist will probably coin a 'meta-' to cover it.

* Paris was called Lutetia (or Lutetia Parisiorum) i.e. mud-place or mud-island by the Romans.

[hvered]

Having looked again at Burrowbridge Mump, it is described as being made of sandstone capped by mudstone, once known as Keuper's Marl (or even Kuiper's Marl) but subsequently replaced by the term Mercia Mudstone. The Mump is also described as a completely natural conical hill that 'may have been artificially scarped' so it doesn't sound like an in-depth investigation has actually been carried out.



Whichever term that's used, everyone agrees it's a prominent landmark that controls the route (the A361) across the Somerset Levels (and as we know on the Michael Line), occasionally noting it's anomalistic. The so-called Sweet Track, considered to be the oldest known trackway in Europe though it was built over an earlier track, the Post Track, was found nearby at Shapwick Heath. A great deal of effort was spent on the dating and analysis but not, it would seem, on joining up the dots.

[Boreades]

If our ancestors excavated and then piled up natural sedimentary material in a hill-shaped mound, and then left it to compress itself for a few thousand years, would those natural sedimentary materials now appear to be sedimentary rocks? (Mudstone, sandstone, etc)

Do we need a geologist with an open mind?

[hvered]

Newcastle's newest landmark is a naked woman created from slag, called Northumberlandia or, rather aptly, Slag Alice. Shades of Black Annis perhaps. But in any case mining spoil cannot simply vanish, now as then.

[hvered]

Do we need a geologist with an open mind?

It doesn't look like any geologist would be much help. The opening paragraph in Wiki's article on Mudrock (a term preferred to mudstone it seems) states

There has been a great deal of disagreement involving the classification of mudrocks. There are a few important hurdles to classification, including:
1. Mudrocks are the least understood, and one of the most understudied sedimentary rocks to date
2. It is difficult to study mudrock constituents, due to their diminutive size and susceptibility to weathering on outcrops
3. And most importantly, there is more than one classification scheme accepted by scientists

and goes on to say that 50% of the world's sedimentary rock consists of various types of mudrock. The reason for geologists' lack of interest might be that it's utterly boring, viz:

Interbedded between the high-energy events are mudrock formations that have recorded quieter, normal conditions in our Earth’s history. It is the quieter, normal events of our geologic history we don't yet understand.

Engineers on the other hand are rather fond of the stuff. Mercia Mudstone, applied for convenience to mudstone at large, is used in the industry for foundations, excavations and earthworks. Its properties are somewhere between soil and rock but, unusually, with mudstone the weaker material is below the stronger (as opposed to most weathering processes where the fresher, stronger material is beneath a weaker surface), all of which presumably wouldn't make it easy to determine the material used in, say, a 'mump, let alone if it was artificial or not.

[hvered]

Two important constituents of mudstone are dolomite and calcite which are the main 'cementing agents'. The presence of dolomite cement ensures little or no degradation on or near otherwise weathered surfaces (as per a technical but fairly readable report http://nora.nerc.ac.uk/3664/1/RR01002.pdf there's no data yet on the amount of dolomite and calcite in Somerset mudstone, once known as 'dolomitic conglomerate', though Sully Island, which is a causewayed tidal island and another 'is it or isn't it?' candidate, gets a special mention).

It seems that due to its composition and plasticity, a mudstone construction is less vulnerable to weathering than most other material. Engineers noted an 'affinity' for moisture in mudstone used in earthworks, which suggests its high absorption rate of water will not necessarily damage a structure (even in the recent floods) and, remarkably, that plasticity increases with weathering. It may be that a succession of pilgrims beating a path to the top of Burrowbridge Mump, Glastonbury Tor and the rest could cause far more erosion than sheep, the usual culprits.

[hvered]

So when you find this (Wiki) on Glastonbury Tor

The conical hill of clay and Blue Lias rises from the Somerset Levels. It was formed when surrounding softer deposits were eroded, leaving the hard cap of sandstone exposed. The slopes of the hill are terraced, but the method by which they were formed remains unexplained.

(my underlining)
bearing in mind mudstone's outside-in characteristic, it seems worth pursuing 'Blue Lias' on Wiki, because lo, it's described as a claystone-limestone-mudstone formation

The Blue Lias comprises decimetre scale alternations of argillaceous limestone and mudstone. These alternations are caused by short-term climatic variations during the Early Jurassic attributed to orbital forcing (Milankovitch cycles). These limestone-mudstone alternations pass up into a clay member formerly known as the Lower Lias Clay now the Charmouth Mudstone Formation. This lithology consists of monotonous mudstones weathering to clay at the surface. Sparse thin limestone and nodule bands are seen where the rocks are exposed. The deposition of a clay-rich mudstone member normally indicates deposition in a deeper marine environment.

Furthermore, areas denoted Blue Lias coincide to a great extent with Mercia Mudstone and, oddly, even more so with places of special Megalithic interest

The Blue Lias is a prevalent feature of the cliffs around Lyme Regis and Charmouth, on the Jurassic Coast in Dorset, where it exists in layers of limestone interspersed with softer clay. It is also present in Somerset, particularly around the Polden Hills and Glastonbury, and it forms a broad plain across the East Midlands. It also appears near Whitby in Yorkshire and Southam in Warwickshire where a pub is named after it. There are outcrops along the coast of South Wales, notably that of the Vale of Glamorgan.[6] The type section of the Blue Lias is at Saltford near Bath.

Turns out that Blue Lias is a particularly useful source of cement and lime mortar, and Street ('straight') which leads to Glastonbury is a prime example of a 'Blue Lias town', as is Ilchester, directly south of Glastonbury Tor, which is on the Fosse Way leading to Lincoln in a famously straight line.

[hvered]

Er Lannic, another tidal causewayed island in the Gulf of Morbihan, Brittany, has come up on the Megalithic Portal site with some revealing photos http://www.megalithic.co.uk/article.php?sid=9253.

Half of a stone circle is apparently only visible at low tide and a second stone circle is assumed to lie between the island and the mainland.



There are several warnings about the strength of the tidal currents, makes you wonder at the resilience of the construction. Also of note are the comments on the number of cormorants on the semi-submerged stones which seem to make it a peculiarly atmospheric place, such as this (on The Modern Antiquarian site)

the cormorants perched atop the stones like shadowy guardians warning away visitors to this sacred enclosure.

It's hard to tell whether the birds' presence attracts visitors or warns them off.

[Over on the AEL site Wile E. Coyote has just reminded us of 'llan' meaning land and/or sacred enclosure. Maybe Er Lannic is a llan island?]

[macausland]

A bit far from Brittany and not a stone circle but Macleod's Maidens, a mother and two daughters who are said in some texts to be representative of the three fates, is deemed to be representative of typical sea stacks, the result of fallen arches. There is at least one arch in the area quite close to them.

The location is at Durinish off the west coast of Skye. We are told that Durinish is the Norse for the headland of the deer. We are also told that the Gaelic spelling is Diuirinis. The pronunciation is more or less the same.

Innis can be an island or an archipelago as well as a headland. It also means to tell or inform.

According to Dwelly inis means distress or sorrow.
And dur can mean attentive, steady, persevering

While diuir means difficult, hard, dire. Diurrais means a secret or mystery.

Perhaps the Vikings did notice deer on the cliffs and decided to call the headland after the deer as they are supposed to have done at Lochalsh as well.

Perhaps the dur or diuir relates to the dor of Durdle Dor and other such places all with similar arch like structures and sea stacks. If this is the case it could be another link in the coastal chain. Whether these things are natural or man made it would be natural for seafarers to map them into their list of landmarks to be noticed on their journeys along the coast.