Baektusan, Korea: major volcanic eruption circa 1000 AD

James B. Gill
Professor of Earth Sciences
University of California at Santa Cruz



{SKAS EXCLUSIVE}

The largest volcanic eruption of the last 2000 years occurred on the border of North Korea and
China around 1000 AD at 42 degrees North latitude. The border between the two countries
bisects the crater lake left after the eruption, Chunji ('Heavenly Lake'). Thousands of tourists
from South Korea and China visit the bucolic site annually. The eruption occurred during a time
of conflict in Korea between the Koryo and Liao courts. The greatest effects and the best physical
record of it are in North Korea. The volcano is known as Baektusan (or BaekDoo San, White
Head Mountain) in Korean and Baitoushan in Chinese. It is the highest point along the
Changbaishan Mountains.

Any historians and scientists who might be interested in this event -- especially archaeologists,
physical geographers, geologists, and remote sensing specialists -- are invited to contact Dr. James
Gill, a geochemist at the University of California Santa Cruz (jgill@es.ucsc.edu). He has been
interested in the eruption for more than 15 years and wants to work on its deposits in North Korea
along with international scientists.

Because of its remote and politically sensitive site, this event was not documented until the 1980's
by Japanese physical geographers. They routinely use "tephra" (layers of volcanic ash) to determine
the age of archaeological and natural phenomena in Japan during the last few hundred thousand
years. They found one ash in northern Honshu and southern Hokkaido that geochemically could
not have come from a Japanese volcano. By searching colonial records from Manchuria (northern China) and sediment cores from the Sea of Japan they deduced its source -- Baiktusan.

The age is somewhat uncertain but seems to be 1000 ±40 AD based on "wiggle-matched" 14C
ages obtained independently by German and American teams in the 1990's from charred trees in
pumice flows near the crater. The eruption deposit blew down, burned, and buried trees for almost
30 km on the Chinese side of the border. Single 14C ages from these trees have a wide range. "Wiggle-matching" uses multiple dates from a single piece of charcoal in which growth rings,
starting from exterior bark, are counted, separately dated, and then used to locate results on
calibration curves that compare 14C years to calendar years. German group obtained a 969 ±20
AD age for one of the trees; the American group's result from another was 1039 ±18 AD.

Somewhat surprisingly, there is no definitive evidence of the eruption in historical documents
from China, Korea, or Japan. Nor is there clear evidence in ice cores from Greenland. However,
the evidence on the ground in China and North Korea is startling. The pumice flows extend for
tens of kilometers in all directions, thicker and farther in North Korea than China, especially in
the headwater valleys of the Yalu and Tumen Rivers.

Volume estimates vary by a factor of three, but the one based on field work in North Korea
where the deposits are most extensive, is 96 ±19 km3 of tephra, comparable to the other contender
for the largest eruption of the last 2000 years -- Tambora volcano, Sumbawa Island, Indonesia, in
1815 AD. That eruption had well-documented global effects on weather and health.

The eruption has been the subject of several studies and a book by Chinese geologists, and two
PhD theses by American and German students, one at the University of California Santa Cruz, the
other at Kiel University. The most sustained study outside of China has been by Jim Gill, a
geochemist at UCSC.  Gill primarily studies the subsurface magmatic history leading up to the
1000 AD eruption. His group measures the chemical and isotopic composition of the rocks and
their minerals to determine the origin of the magma and the time scale of its formation. An NSF proposal is pending to continue this work, emphasizing natural radioactive disequilibria in the
erupted materials. The German group emphasized the volatile content of the magma (water,
halogens, and sulfur) and concluded that the eruption would have caused significant stratospheric
ozone depletion and may have resulted in colder tempeartures in the northern hemisphere
for a few years. An English group also is currently studying geophysical events leading up to the eruption.

The event is important geologically because it is the world's youngest and largest volume
chemically zoned volcanic eruption which captured magmatic processes in action. It had two
phases. The first and largest consisted of a very silica-rich magma called comendite that is
estimated to have produced an eruption column about 25 km high. It apparently resulted from
the chemical evolution of a much larger volume of magma during a period of about 20,000 years.
The second phase was smaller but hotter, leaving welded deposits of a less silica-rich magma
called trachyte closer to the crater. The latter magma is thought to have intruded the former
shortly before the eruption, causing it.

There are unconfirmed reports of subsequent eruptions, and there was a seismic "crisis" at the
volcano in the 1990s. There have been several volcanic eruptions elsewhere in Korea and NE
China during the last 10,000 years but this was by far the biggest and most destructive.