The landslip, up to 300m (1,000 feet) wide, took place at Inskip Point in Queensland on Sunday or Monday, state officials said.
It is the third incident of its kind in the area in recent years. In 2015, one swallowed a caravan, tents and a car.
Officials said no campers or property had been affected by the latest event. They urged people to avoid the area.
"It's likely this erosion has been caused by the undermining of part of the shoreline by tidal flow, waves and currents," Queensland's Department of Environment and Science said in a statement.
