Indeed Vince, it isn't rocket science. Rocket science is all about
increasing the height of something and not decreasing it.
Your comment on worm action can't be understated as our little squirmy
friends, the gardener's friend, have a great deal to do with the creation
and build up of soils.
In fact without them we wouldn't have any soil.
As with regard to deep stratigraphy in towns, something I have often
wondered on, I feel it is more than just building on demolished buildings.
If it was just that case the matrix of stratigraphy would be a mix of
rubble and organic rich material. However there is usually a lot of loamy
sand present and I suspect such material is brought in to level off the
site before construction.
Successive razing and construction of buildings on the site would result in
the accumulation of height.
Something must be being added to get the deep stratigraphy one get in
places such as Central London.
On 22 Feb 2017 07:54, "Vince Russett" <[log in to unmask]> wrote:
> Morning, folks
> I thought this business of why archaeology is buried had been pretty
> comprehensively studied and sorted out years ago.
> In urban areas (which is what people are usually talking about when they
> ask this question), the tendency to demolish a building, spread out the
> remains and build on top of it must account for a majority of the 'sinking'
> of sites, along with dumping of waste materials from industry, domestic
> activities and so on. This only happens in heavily developed areas, but
> these are the ones people tend to see (the 'we won't get in British
> Archaeology if we don't show them 5m of stratigraphy' syndrome).
> In rural areas many sites are not buried, but at the surface (hence we see
> medieval flood banks, Neolithic standing stones and iron age enclosures,
> for example, confronting us today). If you want to see what buries
> structures, just go for a walk in the winter. A structure collapses, due to
> misuse or negligence. Leaves blow into it and rot. Saplings grow, soil
> develops. Worm and other action increases the depth of soil by increasing
> its organic content. But then, very often, foot traffic or burrowing
> animals reveal it again.
> Its not exactly rocket science, is it?
> On Wed, Feb 22, 2017 at 7:26 AM, Michael <[log in to unmask]> wrote:
> > A few times on Britarch the question of why archaeology gets buried has
> > come up. In a few cases such as wind blown sand, the reason is obvious,
> > I've never really understood how a building can just appear to sink into
> > the ground. How now I think I've an idea why!
> > Last night I was thinking of three things:
> > * Kostas theory that the Stones of Stonehenge were moved there by ice
> > * The Caterpillar effect (which affects tectonic plate movement over
> > ice-ages - which is supported by increases in volcanic activity &
> > modulation of mid-oceanic ridge formation)
> > * A question I was asked about whether the Caterpillar effect could be
> > seen on yearly temperature changes.
> > And it clicked!!
> > Every day the earth heats up and cools. And similarly over a period of a
> > year. Each time the earth goes through this cycle, the particles of the
> > earth expand and contract causing a regularly movement of the earth akin
> > giving it a shake. Now one "shake" each day is hardly going to make the
> > earth move much for us humans who don't stand in one place very long at
> > all. But for a rock or a building, this constant daily and yearly
> > effectively turns the earth into something quicksand.
> > That could explain why many surface objects sink! They are literally
> > sinking due to regular thermal movement of the top layers!
> > However ... the "shaking" rapidly reduces in intensity as we go down into
> > the soil. Daily changes only have a significant change within the top
> > Yearly within the top few meters. So, in principle a rock or other
> > ought to fairly rapidly descend the first 20cm or so into soil, and then
> > only very very gradually sink further. And indeed at some point
> > (10,000yrs?) it will reach the bedrock
> > Has anyone done any studies into the average depth buildings sink (or as
> > it might be phrased, earth covers) a building, a standing stone or
> > objects?
> > Also, presumably, thermal expansion and contraction is an important
> > on standing structures. It would probably leading to regular movement in
> > walls, which over time would "grind down" presumably leading to
> > and collapse?
> > Mike
> > CATERPILLAR EFFECT (For any who have not heard about it)
> > Each glacial cycle the earth heats up and cools around 5-8C. Just as the
> > yearly cyclic changes in heating and cooling and thus expansion and
> > contraction reach a couple of meters into the ground, the ice-age cycle
> > reaches a few kilometres into the ground. This causes the whole surface
> > the earth to expand and contract successively pushing against each other
> > and then contracting. The expansion per unit of rock is small, but
> > (surface) rock is largely incompressible, the result is that the rock is
> > forced to expand and over 40,000km of the earth's circumference the
> > expansion is equivalent to a couple of kms of movement over an ice-age
> > cycle.
> > Similar effects are seen of lake & sea ice - where pressure ridges form
> > due to daily or other changes in the air temperature. However in the
> > rather than pushing up to form a ridge, expansion (usually) causes crust
> > be pushed down when it is heated. This pushes rock down to where part is
> > thermally decomposed giving rise to a sharp increase in volcanic activity
> > as we come out of an ice-age ( Lund et al (2016) <
> > http://science.sciencemag.org/content/351/6272/478>). However on
> > contraction, the location of the effect is different: the crust tends to
> > break apart at mid-oceanic ridges. This increase the rate of mid-oceanic
> > ridge formation as shown by *Maya Tolstoy (Link). <
> > http://scottishsceptic.co.uk/wp-content/uploads/2017/02/tol
> > stoy_inpress_grl_2015.pdf>
> > *Thus over each ice-age cycle, rocks pushes out from the mid-ocean ridges
> > and down into the ground and subduction zones. And then it pulls away
> > the mid-oceanic ridges that then fill in. This results is a creepy effect
> > like the movement of some caterpillars: hence the nickname.