  thumb|a denehole in essex a denehole (alternatively dene hole or dene-hole) is an underground structure consisting of a number of small chalk caves entered by a vertical shaft. the name is given to certain caves or excavations in england, which have been popularly supposed to be due to the danes or some other of the early northern invaders of the country. the common spelling dane hole is adduced as evidence of this, and individual names, such as vortigerns caves at margate, and canutes gold mine near bexley, naturally follow the same theory. the word, however, is probably derived from the anglo saxon den, a hole or valley. the lack of evidence found in them has led to long arguments as to their function. ==form== the general outline of the formation of these caves is invariably the same. the entrance is a vertical shaft some 3 feet (1 m) in diameter falling, on an average, to a depth of 60 feet (20 m). the depth is regulated by the depth of the chalk layer from the surface, although chalk can be found within a few feet, or even inches, from the surface. a depth of from 45 to 80 feet or more, is a characteristic feature. footholds were cut into the sides of the shaft to allow the miners to climb in and out. the shaft, when the chalk is reached, widens out into a domed chamber with a roof of chalk some 3 feet thick. the walls frequently contract somewhat as they near the floor. as a rule the main chamber is 16 to 18 feet in height, beneath each shaft. from this excessive height it has been inferred that the caves were not primarily intended for habitations or even hiding-places. in most cases, between two and four sub-chambers are present, excavated laterally from the floor level, the roof being supported by pillars of chalk left standing. ==distribution== there are many underground excavations in the south of england, also found to some extent in the midlands and the north, but true deneholes are found chiefly in those parts of kent and essex along the lower banks of the thames. with one exception there are no recorded specimens farther east than those of the grays thurrock district, situated in hangman's wood, on the north, and one near challock on the south side of the river south of faversham. isolated specimens have been discovered in various parts of kent and essex, but the most important groups have been found at grays thurrock, in the districts of woolwich, abbey wood and bexley, and at gravesend. those at bexley and grays thurrock are the most valuable still existing. it is generally found that the tool work on the roof or ceiling is rougher than that on the walls, where an upright position could be maintained. ==history== pliny the elder wrote about british chalk extraction in a.d. 70 a
Archaeology_of_the_United_Kingdom Monument_types