Is the average altitude of the Qinghai Tibet Plateau 4000 meters or 5000 meters

Is the average altitude of the Qinghai Tibet Plateau 4000 meters or 5000 meters

The Qinghai Tibet Plateau is located in the southwest of China, covering an area of about one fourth of the whole country. Its average altitude is more than 4000 meters, which is the highest plateau in the world. It is known as the "roof of the world";