Who says we're done exploring the Earth?

Scientists in China announced a major new discovery this week: 49 massive sinkholes that were previously unknown, representing the highest natural density of the phenomenon in the world.

Government researchers discovered the sinkholes during the course of a four-month survey in the Qinling-Bashan Mountains, which are located in the Hanzhong area of northwest China's Shaanxi Province.

The 49 sinkholes are clustered in a 230-square-mile patch of land within the 2,000 square miles that were surveyed.

The largest of the sinkholes has a diameter of 1,706 feet and a depth of 1,050 feet.

The scientists also found several species of rare plants and Chinese giant flying squirrels, which have striking red fur.

The team suggests the holes likely formed