Tianchi: The Crater Lake and Its Northern Outlet

Tianchi sits inside the broad caldera at the summit of Changbaishan, a volcanic basin formed by collapse of the mountain’s summit. UNESCO’s Geopark account says water began accumulating here tens of thousands of years ago after an earlier Tianwenfeng eruption, and that the lake refilled after the Millennium Eruption. Volcanic deposits around the rim preserve stages of the volcano’s activity. The lake’s shape and its outlet are part of the same landform: a basin that gathers water and a valley that carries it away.

The north-slope approach for this feature is in Antu County in Yanbian. UNESCO lists the Chinese Changbaishan area as a Global Geopark, designated in 2024, and records a separate biosphere-reserve designation from 1979. These labels refer to different conservation and earth-science programmes. Tianchi itself lies along the China–North Korea boundary, and the wider mountain crosses administrative borders beyond this north-side approach.

A 2025 report from Northeast Normal University dates Changbaishan’s Millennium Eruption to 946 CE. UNESCO’s Changbaishan Geopark account describes volcanic deposits that preserve evidence of the mountain’s eruptive history.

A 2018 Jilin local gazetteer describes the river route from Tianchi through Tongtian River, over a cliff as Changbai Waterfall, and onward north toward Erdaobaihe. A water-resources overview published by the Changbaishan Administrative Committee on 14 March 2023 identifies Erdaobai River as a source of the Songhua. Together, these sources document a northern watercourse through Tongtian River and Changbai Waterfall to Erdaobaihe, linking that river route with the Songhua system.

Erdaobaihe Town in Antu is the principal entrance area for the north scenic route in Jilin’s tourism listing. The north-slope route, the border lake and the whole Changbaishan massif are different geographical scales. Following the outlet keeps this account with the water’s actual course: from the Tianchi basin, through the northern cascade, and into the river system below.