In the year 946 CE, the Changbaishan-Tianchi volcano, straddling the border of China and North Korea, erupted with tremendous force. This eruption wasn’t just a fiery spectacle; it unleashed a massive flood, the remnants of which are still visible today in the form of boulders and smaller rocks scattered across the volcano’s slopes. Known as Baekdu in Korean, Changbaishan-Tianchi poses a potential threat of future eruptions, prompting volcanologists to study its past to understand the risks it presents.
To investigate the catastrophic flood that followed the 946 eruption, researchers led by Qin et al. embarked on a meticulous examination of the layered deposits from the volcano. Their findings suggest that at least 1 cubic kilometer of water surged out of the volcano’s caldera, creating a torrent that eroded sediment at a staggering rate of 34 meters per hour for approximately three hours.
The study also reveals that the eruption unfolded in two distinct phases, with the flood occurring between the two phases. This finding contradicts previous hypotheses that suggested a single, instantaneous outburst after the eruption cracked the volcano’s rim. The researchers argue that such a scenario is improbable because the distribution of sediment doesn’t align with what would be expected from a sudden, massive burst.
Instead, the researchers propose three alternative scenarios to explain the flood’s occurrence. The first possibility involves the simple overflow of water from the caldera, driven by the upward pressure of rising magma beneath it. The second scenario posits that the eruption triggered an earthquake, causing the inner wall of the caldera to collapse into the lake, leading to an overflow. The third scenario suggests that heavy precipitation before the eruption filled the caldera to capacity, weakening the crater rim and allowing water to escape.
The study’s implications extend far beyond understanding the 946 CE event. By deciphering the mechanisms behind ancient floods like this, researchers can better prepare vulnerable populations for future natural disasters, not only at Changbaishan-Tianchi but also at volcanoes globally.
This research highlights the importance of understanding the complex interplay of volcanic activity and its potential for triggering devastating floods. As we continue to monitor and study active volcanoes around the world, the insights gleaned from this study serve as a vital reminder of the immense power and potential danger of these geological giants.