A possible cause is the fact that the underlying material is chalk and there could be cavities, also the area was mined during Victorian times so there could be tunnels underneath.
According to The Telegraph, " In recent years large holes have been discovered across the borough, which experts have blamed on underground chalk caverns and disused mines which are “littered” across the district."............. "While officials from the Royal borough of Greenwich council assured residents that the hole had been “stabilised”, a 19th century report recovered by this newspaper suggests that the entire area may be precariously resting on top of a series of underground caverns.
Published in the Kentish Mercury on 24 March 1849, the article reveals that rail workers excavating the South Eastern Railway discovered a large crevice underneath Maryon Park, less than a mile from where Thursday’s sinkhole appeared.
It read: "during the operations... they came upon a cave, of considerable dimensions, cut in the chalk and flint rocks.
"A great quantity of sand has fallen at one end, blocking up the side from which it has apparently been entered, and the workmen are now busily employed in shoring up a part of the roof of one of the chambers, the railway passing over its entire breath."
It is the second sinkhole to emerge in south east London in just over a week. On May 4 a sinkhole appeared outside a house in Plumstead.
Now there is concern that property prices will fall after news of these sinkholes.
“Greenwich is one of the most expensive land areas in Europe, but in recent years six deneholes have been discovered in the area around Maryon Park alone,”.
Deneholes are medieval chalk extraction pits and are mainly found in Kent and Essex along the lower banks of the Thames.
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Update 13 May
A small sinkhole appeared in a road in Woolwich. Photo taken from newsshopper.
This is the 3rd sinkhole to open in the Greenwich area in 10 days.
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