A Maar volcanic group comprising 116 volcanos, each with a crater diameter of more than 50 meters, has been found in northern China's Inner Monglia Autonomous Region. According to the research team, the Maar volcanic crater group is the largest in the world in terms of scale and integrity, and its formation is believed to date back between 9.4 million and 33 million years. Usually, Maar volcanos are difficult to identify since they are shaped like a "plate with wide sides and flat bottoms."