question: How did old settlements get physically buried underground
comment: Many possible causes. A few examples: - Volcanic eruption, with lava flows - Volcanic eruption, creating massive ash deposits (Pompeii) - Flooding, causing buildup of silt and debris - Subsidence into a body of water - "Man made" burial, in which a new settlement is built over the top of another one - Landslides
passages: One of the most characteristic features associated with settlements are storage pits of the Únětice type. They were located beneath the houses, and were deep and spacious, with a cylindrical or slightly conical neck, arched walls, and a relatively flat bottom. These pits often served as granaries.
   Numerous saucer shaped hollows commonly referred to as Sirikwa holes have been found in various areas on the hillsides of the western highlands of Kenya and in the elevated stretch of the central Rift Valley around Nakuru. These hollows, having a diameter of 10–20 metres and an average depth of 2.4 metres, are usually found in groups sometimes numbering less than ten and at times more than a hundred. Excavations at several examples of these sites in the western highlands and in the Nakuru area have shown that they were deliberately constructed to house livestock. 
   After the residents of the subterranean houses had abandoned them the site was re-settled, most likely by the same people. They built semi-subterranean houses in the pits left over after the collapse of the subterranean houses from the previous phase. These houses were round or oval in shape and had walls made of unburned mud bricks. On top of these walls four depressions were made, one in each corner. These depressions held wooden beams that supported a roof made of branches covered in clay.
  
  Section::::Settlement phases.:Above-ground phase.
   Rock disposals or dumps are the most common and characteristic traces of mining. They are usually situated near the mouth of galleries or mines, but can also be found further away, stretching onto the sides of ravines for hundreds of meters, sometimes even a kilometer or more. During the general assessment of traces, dumps are not treated independently because they are usually parts of the shafts, galleries, quarries, or other mining works. Having occurred in different periods, these dumps were often superimposed not only on top of each other, but also upon the openings of ancient vertical and horizontal shafts. As a result, a chaotic distribution of residue is left on the surface of the earth.
   On lakes of southern Germany and Switzerland, numerous pile dwellings were constructed. They consist either of simple one-room houses made of wattle and daub, or log-built. The settlement at Zug, Switzerland, was destroyed by fire and gives important insights into the material culture and the settlement organisation of this period. It has yielded a number of dendro-dates as well. 
  
  Section::::Settlements.:Fortified settlements.
   The effect of this is that even a moderately sized settlement of any antiquity is built on top of a heap of refuse and demolished buildings and is therefore raised up from its original height on a plateau of archaeology. This is most apparent in the tel sites of the Near East where towns that have been occupied for thousands of years are raised up many metres above the surrounding landscape.
   Section::::Archeology.:Neolithic period.
  
  Flint tools, including microliths and arrow-heads from the Neolithic period (12,000–4,500 BCE) were uncovered sitting on the mound's bedrock.
  
  Section::::Archeology.:Early Bronze Age period.
   Period II was represented by 80 cm deposits but deposits connected to habitation was about 20 cm to 25 cm thickness. Large number of pits (0.5 m to 2 m diameter, 0.5 m to 2 m depth) which were invariably filled ashy soil, potshreds, animal bones and other insignificant materials were found and the significance of these large number of pits is not fully understood.
   Most villages were not ancient, but they were founded and discarded during successive colonization steps. As extensive farming was used, the areas with depleted soil were abandoned for new land, often obtained through deforestation. Sometimes, they were divided into more groups, each looking to found its own obște on fertile land, something known as the "swarming of the obști" ("roirea obștilor").
   The settlements discovered in Bir Abu Matar belong to the Chalcolithic period, Beersheba Culture, and can be divided into 3 distinct settlement phases, each with its own particular architecture: the earliest settlers built underground dwellings, dug in the soft loess. Later, when some of these homes collapsed - their ceilings had caved in - new, semi-underground houses were built on top of the old ones. In the 3rd and final phase the settlers built their homes completely above ground.
   BULLET::::- Pit-houses were partly dug into the ground (semi-subterranean), with deep storage pits and corridor-shaped exits. Dwellings were spacious, between and , constructed on two rows either in a semi-circular or rectangular plan. They were usually aligned overlooking river banks.
  
  BULLET::::- Burials in underground timber or stone chambers inside round or rectangular kurgans. The bodies were accompanied by sacrificed animals (mostly horses and dogs), chariots, cheek pieces, weapons, pottery and jewellery.
  
  Section::::Iron Age.
   Fortified settlements, often on hilltops or in river-bends, are typical for the Urnfield culture. They are heavily fortified with dry-stone or wooden ramparts. Excavations of open settlements are rare, but they show that large 3-4 aisled houses built with wooden posts and wall of wattle and daub were common. Pit dwellings are known as well; they might have served as cellars.
  
  Section::::Settlements.:Open settlements.
   There was also extensive farming settlement during the Bronze Age, known from middens that infill the mouths of many Neolithic mineshafts. Animal bones from these middens show that the Bronze Age people kept cattle, which they milked, sheep and a few pigs. They also grew barley, wheat and peas.
  
  Section::::Mining method.:The site today.
   The total length of underground headings was likely to have been several hundreds of kilometers [fig. 4, 5].
  
  During the Bronze Age, the sinkings and headings of mines were a maximum of 40–42 m deep. By the New Age (18–19 cent.) they had reached as much as 80–90 m deep. The total amount of sandstone, crag and marl, and other wastes extracted from the surface measured nearly 100–120 million cubic meters, equivalent to a weight up to 250 million tons.
   From 1995 to 2000, geomagnetic surveys were carried out which covered 220,000 square metres and identified 450 distinct subterranean structures consistent with the remains of wooden houses, an enclosure in the south, and a cluster of three larger quadratic structures. Results from pilot prospections beyond this characterized area, as well as the history of surface finds and accounts from the local population, suggests that the settlement could have been at least twice as large.
  
  Section::::Excavations.
   Section::::General information.:Evidence of structures.
  
  Post holes, a sunken area and concentrations of flints, burning and other artefacts indicate the presence of a structure approximately wide. The posts were almost certainly made of wood and roughly in diameter there may have been as many as 18 of them and the holes indicated that several may have been replaced over the course of the structure's use.
   Many settlements were originally built on hills, either to avoid floods (particularly if they were near a large body of water), or for defense (since they offer a good view of the surrounding land and require would-be attackers to fight uphill), or to avoid densely forested areas. For example, Ancient Rome was built on seven hills, protecting it from invaders.
  
  Some settlements, particularly in the Middle East, are located on artificial hills consisting of debris (particularly mud bricks) that has accumulated over many generations. Such a location is known as a "tell".
   In the Period II, the finds excavated revealed that people had moved out from pit dwelling to structures built at the ground level. However, the pits and its associated chambers formed the base floor of the superstructure, which was made up by filling the pits and covering it with mud plaster, and occasionally painted in red ochre. Post-holes around the pits revealed that the superstructures were made of wood built over compacted Karewa soil floors.
   In 2008, deepening continued within the same area (10 x 10 m) and the Middle Bronze Age layer was reached, the goal being the identification of residential structures from that horizon.
  
  Section::::Location.:Pecica.:Findings.
   Most of these underground houses had been abandoned by their owners. Houses with sealed storage spaces containing neatly arranged house appliances were discovered on the site. Their rooms had been sealed with large stone slabs. Many of these houses had never been re-occupied; they were found whole and still "locked up", during excavations.
  
  Section::::Settlement phases.:Semi-subterranean phase.
   Section::::Main Types of Mining.
  
  The first type of mining utilizes shafts or sinkings, spaces that stretch, either vertically or sloping (from 90 to 60 degree of declivity), into the sandstone and crag rock, which is covered by a layer of argillaceous soil [fig. 6]. These shafts lead directly to the ore and ventilate the underground shafts and facilitate the delivery of minerals and rocks to the surface. At present the majority of them are filled with collapsed clue rock and detritus, others have been destroyed by the dump from later excavations.
   In some areas which are now unproductive moorland, aerial photographs show the presence of numerous prehistoric clearance cairns and associated dwellings such as hut-circles. This clear evidence of previous ancient habitation and cultivation shows that the climate worsened until the farmers were forced to move to lower ground.
  
  Section::::Stone carrying.
   In the first phase of settlement, the people of the Beersheba culture lived in underground dwellings, dug in the soft loess of the Beersheba Valley. Several of these settlement were constructed in the banks of the Beersheba Creek, in areas where water could be obtained by digging wells. In the second phase, semi-subterranean houses were built on top of underground houses that had collapsed and, in the third and last phase, houses were built completely above ground on stone foundations. The walls of the houses in the later two phases were built from pisé and the roofs consisted of branches covered in clay which lay on top of two large crossed support beams.
   Easy access to fresh water also would have been mandatory, which is another reason why settlements were in bottom lands near water. A number of wells from the times have been discovered, with a log-cabin type lining constructed one layer at a time as the previous layers sank into the well.
   There are various ways to develop structures for underground living.
  
  BULLET::::- Caves (Natural) have been used for millennia as shelter.
  