A second massive crater has appeared in a remote part of Siberia on the Yamal Peninsula, called "the end of the world." The new crater was discovered by reindeer herders about 30 kilometers (19 miles) from the first, reports the Moscow Times. Following this discovery, a third hole was found to the east of the other two. It's just 15 meters deep but 60-100 meters deep, locals report.
It's uncertain yet what's caused the sinkholes, but experts said global warming may play a part. Above is a view of the wall inside the first crater.
One theory: when permafrost melts, gas is released, causing an underground explosion.
Experts from the Center for the Study of the Arctic and the Cryosphere Institute of the Russian Academy of Sciences have studied the hole, returning with the first photos from the site.
"We can definitely say that it is not a meteorite," a spokesman from Russia's Emergencies Ministry told the Siberian Times.
The area contains some of Russia's most plentiful stores of natural gas. About 10,000 years ago, the area was under the sea, which left salt deposits.
The first hole is about 50 meters wide (164 feet, or about 15 stories) and 70 meters deep (229 feet, about 21 stories), reports the Moscow Times. The second appears similar, but is much smaller.
Scientists are concerned that global warming could cause more permafrost melt, which could release methane, a greenhouse gas -- and possibly more enormous Siberian sinkholes.