Second sinkhole appears in Australian city this week

Two sinkholes have opened near the Australian northern coastal city of Newcastle, New South Wales, in the last two days. The first appeared yesterday with another opening today, both developing by houses on Lambton Parade in the suburb of Swansea Heads.

The first sinkhole measured around twenty metres across and ten metres deep, while the second sinkhole was much smaller, measuring around two metres across. The first hole swallowed tonnes of material in two hours next to a married couple's home before they returned to discover it.

The street is over a coal mine abandoned in 1950s and this appears to be contributing to the instability of the land.

The Mine Subsidence Board is investigating the two sinkholes and safety of other homes in the area. Dozens of homes have been built over the mine since its closure. The house involved in the first, larger sinkhole dates from the 1990s, making it relatively new on the street, and the damage to it may be fixable, according to mine subsidence board members.

Sinkholes can occur naturally when bedrock erodes due to acidic rainwater seeping from the surface, or, as in this case, they can occur when houses are built on top of old mines.