The theory that it was caused by an attacking enemy is one I don't subscribe to. If this were the case then it would surely just be in isolated spots around the bank.

If you listen to the UFO crowd then it's from early forms of nuclear war! :-)

Saw a documentary a few years ago where they reconstrucred how the ramparts may have become 'vitrified. The conclusion was that the extreme temperatures which melted the rock were reached because the forts were in fairly exposed areas where high winds were common, acting a little like a bellows i suppose. Not sure why the whole of the ramparts are fused, can only guess that the timber used to build the walkways common on many hillforts became well seasoned when old and dry and was possibly resinous (scotts pine?) making it condusive to being flammable. Only a theory though.
Couldn't have been the Romans that did it though, as they never reached into the far North of Scotland, or so were told. Maybe the attackers threw torches coated in resin or some tar like bitumen substance.

Just read (quite quickly, so forgive any duplication of ideas!) the whole thread, and I'dlike to add my two pennorth!

Suppose the builder of such forts are under imminent attack from a larger force. Judging by the layout of Brigs maps of dykes etc, we'rre looking a t a large area to be defended. Consider the possibility that an engineer/mage/druid/smartass from the tribe or from another land has introduced the technique of Greek Fire (or similar). No matter how strong the ramparts or how numerous the defenders, the invaders may be in a position to storm the defences and gain access. If the builders/defenders, anticipating an attack have prepared the walls using flammable materials, when the tribe advances on the fort, torches could be used to ignite the walls - thereby creating A) an impassable sheet of flame B) and impressive display C) a fiery Beacon to warn neighbouring forts/settlements D) Light to see by during a night attack E) hot slippery walls which would be difficult to scale.
F) Something to toast your buns on while waiting for the attackers to piss off home!

What say?

I haven't read everything on this thread yet so excuse me if i'm repeating someone, but I was always brought up to believe that the vitrification was done purposely to strengthen the fort and is not a consequence of attack. How it was done i have no idea!
love carolinexx

Wood apparently burns at different temperatures, Oak and Yew burn the hottest.

Well I thought I was going to bed but didn't!
Had another thought, Vitrification is also used in ceramics, where a substance of a lower melting point seeps into a porous substance of a higher melting point. Perhaps the technique has more to do with a third ingredient?

I found this from Aberdeenshire council - another angle -

"These represent only one of several types of defensive site in the north-east, dating from c 900BC to c AD 900. They are called 'vitrified' because the stones of their rampart walls have been fused together by intense heat, caused by the firing of a wall strengthened by beams of timber running through it.

Experiments have shown that a great deal of brushwood and other fuel is required to achieve the fusing (and, also, the collapse of the wall). The technique must therefore have been carried out some time after the fort had fallen to an enemy, perhaps as a form of psychological warfare.

The technique of timber-lacing is not precisely dated; it is found on (presumptively) early first millennium BC sites such as Dunnideer, and Tap o' Noth as well as on sites as late as the ninth century AD such as Green Castle, Portknockie, in Moray. "

Anyone remember the robot in The Day the Earth Stood Still?

A great antiquity has been. assigned to vitrified forts, without sufficient proof. Articles of bronze and iron have been found in the Scottish forts, while in Puy de Gaudy a Roman tile has been disco’~~ered soldered to a piece of vitrified rock. In a few of the German forts Professor Virchow found some of the logs used as fuel in vitrifying the walls, and he concluded from the evenness of their cut surfaces that iron and not stone implements must have been used. These results Indicate that these structures were possibly in use as late as the early centuries of the Christian era. It has been suggested that they were built as refuges against the Norsemen. Much in the situation and character of the forts favours this supposition. This is especially the case with reference to the Scottish forts. Here the vitrified summits are invariably so selected that they not only command what were the favourite landing-places of the vikings, but are the best natural defences against attacks made from the direction of the seacoast. In Saxony and Lusatia the forts are known as Schwedenburgen, and in the Highlands of Scotland as the fortresses of the Feinne—designations which also seem to point to an origin dating back to the times of the vikings.

woah ... I had no idea that my beloved Castle Hill (aka Almondbury) was involved in this vitrification business ...
http://www.themodernantiquarian.com/browse.php?site_id=1819

you're catching my attention, if only
fleetingly. There's something pretty special about that place ... I spent a large part of 1992 sat up there, when I should have been doing discourse analysis on the media reporting on the Rio Earth Summit

actually, it's far too embarrassing to relate what happened up there that summer, but believe you me, there's something strange about that place.

Or, of course, there's something strange about me, a possibility I'm prepared to accept, but lets stick with the hill

I'll go and read up ... this is something I never knew or thought about, and it's making me change my way of thinking about somewhere I thought I knew well ...

nice one BN ... this is what TMA is all about (and acronyms, of course)

RG