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As a follow on from Destruction by design - how best to go about crafting a ruined landscape? I'll be asking two questions about signature destructive patterns, this is the first:

How, if at all, does deliberate destruction, such as the slighting of a fortress, the reformation era Dissolution of the Monasteries, or the modern demolition of buildings to make way for new construction, leave a long-lasting signature such that an observer viewing only centuries old ruins could tell that the results were deliberate rather than the simple result of time?

This question assumes that destruction of the building(s) in question is incomplete, otherwise there are no ruins to look at at all, and that the majority of the building material is still on site in one form or another. Good answers should concentrate on the relative distribution of such material, what's still standing and where the material from destroyed structural elements is to highlight any signature differences that could be diagnostic for an observer who knew nothing about the site history. Obviously there will be differences depending on the construction materials and techniques, these should also be highlighted where appropriate/diagnostically important.

Assume the building(s) were 50% destroyed before the site was abandoned and that the site is roughly 200 years post-abandonment to simplify issues of material degradation rather than answers being awkwardly time dependent.

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    $\begingroup$ There are different kinds of deliberate destruction of structures, which could affect the answer. A building being destroyed by a hostile invading army would probably be damaged in such a way as to make it obviously ruined, but it would be done as quickly as possible. A building being demolished to make room for new construction would probably be dismantled in a more organized fashion. A third possibility is that the intact structure is slowly dismantled over time by locals who are "mining" it for materials. $\endgroup$ – barbecue Nov 1 '17 at 0:10
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    $\begingroup$ @barbecue Third possibility is a real one and happened (and still happens) a lot. Cutting rock to make bricks is a hard work and that old fortress is much near than the Quarry. Just google around any old abandoned stone structure like the Hadrian wall and you will discovery much of it was "recycled" by the population along the centuries. $\endgroup$ – jean Nov 1 '17 at 15:47
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    $\begingroup$ @jean There's even a term in archaeology for it, a structure so used is said to have been "robbed-out". $\endgroup$ – Ash Nov 1 '17 at 15:51
  • $\begingroup$ @barbecue: Indeed, people are unlikely to expend any effort destroying a building (versus abandoning it and letting it decay) unless doing so would offer some advantage versus the natural default. If a building is destroyed to make space for something else, the space it occupies will be cleared. If some material were recycled, they will be missing. If some people needed to make it useless to other people, the easiest means of doing that will usually leave noticeable marks (blast patterns, etc.) On the other hand, only in the latter case would evidence necessarily show... $\endgroup$ – supercat Nov 1 '17 at 16:58
  • $\begingroup$ ...the reason for the building's decline. The fact that a new building sits where the middle part of a building's foundation used to be would imply that the space was reused for the new building, but wouldn't imply that old building was torn down for the purpose of putting in the new one. Perhaps the old building had an accidental fire that damaged it so badly that repair would be impractical. $\endgroup$ – supercat Nov 1 '17 at 17:01
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In a deliberately destroyed building the roof would probably be gone immediately. In an abandoned building the roof would probably (depending on construction), survive for many years even decades. This would have an effect on the pattern of debris.

In a deliberately destroyed building the debris on the floor would consist of roofing materials, wall materials and fittings spread in an uneven layer on top of which after 200 years would be a layer of organic material, and detritus with much less building material.

In an abandoned building the debris on the floor would show a different pattern. Organic material and detritus would be present throughout debris stack and there would be more roofing material at the bottom of the stack and more bricks at the top.

The destruction would also likely show a pattern. Certain parts of the building would be vulnerable such as wooden frames, junctions and angles on roofing and previously damaged areas. Collapse would be from these areas and would spread out towards the other areas. So certain parts of walls such as corners and junctions would be expected to last longer as they have greater support.

In a deliberately destroyed building there would likely be signs of violence if you looked closely enough. For example if a battering ram or demolition ball had been used the impacts would likely leave a tell-tale marks on surviving brickwork and crush marks on wood and tear and twist damage on metal fitments to a much greater extent than in an abandoned building. Wall junction areas that had been knocked off their foundations at a low level would be a clear sign of demolition.

The pattern of collapse of walls would also be different in a deliberately destroyed building most of the walls would probably be knocked in, where as in an abandoned building some walls might fall outwards.

The size of the pieces of rubble might also give a clue. In a deliberately destroyed building there might be a greater number of smaller pieces and single bricks scattered. Where as in an abandoned building large parts of walls might collapse relatively intact. Not definitive but indicative.

In a deliberately destroyed building there might also be signs of fire damage, much less likely in an abandoned building and possibly crushed bricks pushed into the surface of the earth at a deeper level than might be expected where heavy equipment had passed through.

All of this is a little bit dependent on the “50% destroyed before abandonment” restriction which makes life a bit difficult. How was the 50% destroyed before abandonment? Nevertheless if you looked hard enough you should be able to tell. A structural engineer and an archaeologist would be useful companions to help with the identification.

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    $\begingroup$ I agree as regards the roof. I have seen abandoned mansions where the roof was removed before abandonment to prevent squatters. Likewise cathedrals. Without the roof the structure is unusable as a shelter or really anything else. It also betrays some foresight: a intact stone or brick frame can get a new roof put on it years later and still be of use - so if you do not need the land, why knock it down? $\endgroup$ – Willk Oct 31 '17 at 17:45
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Very crude rule: Decay damage tends to be top down while deliberate damage tends to be bottom up. I.e., in the case of simple wear the uppermost part is visibly more damaged than the bottom, while in the case of an assault, the damage in the first 4-6 metres from ground level is more pronounced.

There are major exceptions, e.g. floods, but it is a good enough rule

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Consider that if a medieval style building were left abandoned, decay would leave it looking a certain way after a few centuries. As the timbers acting as the support structure for the buildings rot, ceiling, and walls may begin to collapse.

Similarly, ramparts and walls would slowly erode, with stones probably crumbling as the mortar holding them starts to go. Imagine the tops of walls slowly coming down, with maybe some entire sections crumbling.

However, battle damage would leave signs which should be noticeable even centuries later. For example, a wall that is otherwise standing, may well have a hole punched right through it. Buildings may exhibit signs of a great fire (melted metal structure supports, blackened timbers/stones, and even show evidence of stone having become molten).

Last but not least, finding large numbers of human remains, broken weapons, etc. just under the surface, or in long abandoned basements/rooms would be a surefire sign that the place wasn't simply abandoned to the ravages of time.

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  • $\begingroup$ Combat was really not what I was thinking about with this question but yeah alright. Tomorrow's question is going to be all about the results of major combat. $\endgroup$ – Ash Oct 31 '17 at 13:34
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I can only speak about modern demolition since that is all I have experience with, but there are certainly signs that will be lasting.

  1. Thick metal supports are twisted, pinched, and cut by grapples, pulverizers, and shears. If any of these supports remain uncovered/visible, it will be fairly obvious that natural processes did not cause their deformation.

  2. The rubble from a professionally demolished building is typically very orderly. As the big machines are tearing a building apart, smaller bulldozers and trucks promptly separate the rubble into piles that are some distance from the building. This is to allow for proper disposal or recycling of different materials, and gets it all out of the way of the bigger machines. If your archaeologists notice a strange grouping of rubble that doesn't seem to relate to the organization of the structure, it was probably demolished.

  3. Demolition happens top-down. Sometimes a tall building will still have perfectly intact windows on the bottom floor until the crew removes every floor above it. Generally they try to avoid doing any structural damage below the level they are working on to avoid cascading damage that will make their work more difficult or endanger a worker/machine. If for some reason the building was left only partially demolished, your archaeologists would find strangely intact lower floors compared to completely obliterated upper floors.

All of that said, I find it hard to imagine a real-world scenario where a multitude of buildings were abandoned half-way through a demolition. The process is fairly fast, and, more likely than not, there will be surrounding buildings that weren't demolished that will make the halfway demolished buildings quite conspicuous.

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Tool marks would be a relatively easy and obvious place to start. Modern archaeologists studying relics and environments from as far back as the stone age have been able to determine what was naturally made and what was human-crafted by the witness marks left by tools.

If you knock down a concrete building with a backhoe, the metal will leave gouges and unnatural edges in the material that wouldn't normally result from a simple structural collapse. Demolition by explosives (whether weapons or simply controlled deconstruction) would leave chemical traces, alter the crystal structure of the material (e.g. glassification, where a material is partially melted by the blast), and would produce a fragmentation pattern that can be perceived by archaeological methods. Even the debris pattern produced by a non-explosive collapse could be walked backward to give a rough idea of how a structure fell, allowing educated guesses to be made as to the cause.

However it's important to consider the effects of time on your structures, and the natural weather-resistance of their materials. A wooden structure that was blown apart will rot away to nothing in a hundred years, and there won't be much left to examine. A steel structure will endure longer, unless the environment is particularly corrosive. Stone and concrete will endure the longest due to their mass and resistance to corrosion (except maybe acid rain), and as such will be the most likely to preserve evidence of their untimely demise.

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In the case of demolition, it's easy: if a building naturally decays, the most significant force acting on it will be gravity, and that's going to pull material straight down. You're going to find the debris pretty much right below where it had originally been, and attachments will show signs of having weakened considerably before failing. If the building was intentionally demolished (non-explosive), then debris is going to be away from the building as the demolition crew pulls material as they work. Attachments are going to show distortion from being forced apart rather than failing. In the case of explosive demolition, even if it's a gravity collapse, there's going to be signs of the shearing of structural elements due to the explosives cutting through.

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