[Image: Drone footage of a Cornwall garden sinkhole, via the BBC].

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One of the peculiar pleasures of reading Subterranea, a magazine published by Subterranea Britannica, is catching up on British sinkhole news.

In more or less every issue, there will be tales of such things as ?a mysterious collapse in a garden behind a 19th-century house,? that turns out to be a shaft leading down into a forgotten sand mine, or of ?abandoned chalk mine sites? heavily eroding in winter rain storms, ?resulting in roof-falls.?

?As most chalk mines are at relatively shallow depth,? Subterranea reports, ?these roof-falls migrate upwards to break [the] surface as ?crown holes? or craters, which in the said winter [of 2013/2014] have been appearing in lawns and driveways, and even under houses, newly built in chalk districts.?
The earth deceptively hollow, the landscape around you actually a ceiling for spaces beneath.

Worryingly, many of these mines and underground quarries are difficult, if not impossible, to locate, as insufficient regulation combined with shabby documentation practices mean that there could be abandoned underground workings you might never be aware of hiding beneath your own property?until next winter?s rains kick in, that is, or the next, when you can look forward to staring out at the grass and shrubbery, with growing angst, waiting for sinkholes to appear. Rain becomes a kind of cave-finding technolog...