Round holes of all sizes have begun appearing in a central Croatian region after a 6.4-magnitude earthquake in December that killed seven people and caused widespread destruction.
Scientists have been flocking to Mecencani and other villages in the sparsely inhabited region southwest of the capital Zagreb.
"These are so-called dropout sinkholes, and they appeared because of the specific geological composition of this area, as the soil rests on limestone rocks heavily saturated with groundwater," Croatian Geological Survey geologist Josip Terzic said.
While the appearance of sinkholes is not unusual following strong seismic activity, residents have been baffled by their number - about 100 have been spotted over the past two months - and the speed at which they emerged after the main earthquake on December 29, which was followed by a series of aftershocks.
Geologists have said the temblor accelerated the process of sinkhole formation that would normally have taken years, if not decades.
Terzic said scientists are planning various exploration methods to determine the underwater morphology and other characteristics.
He spoke as he stood beside a large sinkhole that he said was up to 15 metres deep and equally wide.
Some sinkholes have appeared by people's houses or on their farmland, prompting authorities to advise caution.
Teacher Nenad Tomasevic had to move to a neighbour's house after an expanding hole appeared in his backyard.
"The earthquake itself felt pretty unpleasant to say the least. And after that, these holes started popping up," he said.
Some three months after the earthquake, the hardest-hit area is still struggling with its devastation, with many houses still in rubble and the region's main town, Petrinja, semi-abandoned.
Occasional earthquakes, including those of magnitude 4 or more, can still be felt, further upsetting residents and adding to their coronavirus pandemic woes.
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