Gi­ant sink­hole swal­lows Ja­panese street

Chronicle (Zimbabwe) - - Worldwide -

A GI­ANT sink­hole has opened up in the Ja­panese city of Fukuoka.

Res­i­dents of the city on the north coast of Kyushu saw the sink­hole swal­low an en­tire five-lane road in the mid­dle of the city.

Ja­panese au­thor­i­ties evac­u­ated peo­ple from nearby build­ings as a safety pre­cau­tion, but de­spite wide­spread dis­rup­tion to traf­fic, and to sup­plies of elec­tric­ity, water and gas, in­cred­i­bly there were no in­juries.

The mas­sive sink­hole near Hakata Sta­tion mea­sured 27 me­tres wide and 30 me­tres long, with water from bro­ken pipe­lines flood­ing the 15-me­tre deep hole.

Sink­holes are not as rare as you may think. In Septem­ber this year, a huge sink­hole opened up in Florida un­der­neath a fer­tiliser plant.

And in 2013, an­other sink­hole in Florida sud­denly opened up in the east Tampa sub­urb of Seffner and swal­lowed a man while he slept in his bed. De­spite fran­tic dig­ging, his brother was un­able to res­cue him. In the ma­jor­ity of cases it is the weather which trig­gers such huge holes to ap­pear in the ground.

The ground col­lapses when the rock un­der­neath the sur­face soil, known as bedrock, gives way.

This of­ten hap­pens when the bedrock is made of tiny pieces of rock or shells which have been com­pacted to­gether into a solid sub­stance called sed­i­men­tary rock.

These rocks have a rather fun­da­men­tal flaw in that they dis­solve in water. Ev­ery time it rains, water fil­ters down through the bedrock, caus­ing it to slowly erode.

This causes cracks to ap­pear in the bedrock which grad­u­ally widen, cre­at­ing empty cav­i­ties be­neath the sur­face.

The rain­wa­ter will then grad­u­ally wash the sur­face soil down into the cav­i­ties, weak­en­ing the sur­face.

Even­tu­ally the soil above the cav­ity is no longer be able to sup­port it­self and the ground col­lapses.

Lo­cal au­thor­i­ties are in­ves­ti­gat­ing the cause of the lat­est sink­hole in Ja­pan, but re­ports sug­gest on­go­ing sub­way con­struc­tion work nearby may have been a fac­tor. — AFP

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