Giant collapsed caves explain mystery trenches on Australia's Nullarbor Plain

A study in Communications Earth & Environment found that five long trenches on southern Australia's Nullarbor Plain formed when ancient caves deeper than 40 m collapsed. The caves were carved by groundwater flowing toward the coast during the Oligocene and Early Miocene.

• Trenches run up to 20 km long, 100–500 m wide and 1–9 m deep
• Beneath them lie sediment-filled canyons more than 40 m deep
• Caves formed 33.9–16 million years ago as groundwater flowed coastward
• The method may help locate caves on Mars as possible habitats for life