When people think of the Korean peninsula, they don't tend to think of volcanoes. Yet,
both South and North Korea contain active volcanoes. One of these volcanoes was the
site of one of the largest eruptions in human history about 1000 years ago.
The eruption in question was 115 times larger than the famous 1980 eruption of Mount Saint
Helens. The volcano which produced this eruption is known as Paektu, which will erupt again.
This video will discuss this active volcano, and mention what its future hazards are.
The Paektu volcano can be found at the very northern edge of North Korea,
where is straddles the border with China. The closest major city to this volcano is Samjiyon,
which is located 30 kilometers to the southeast. Beginning several million years ago, the region
surrounding the Paektu volcano was the site of thousands of volcanic eruptions. These eruptions
occurred from a variety of volcanic centers and produced vast amounts of basaltic lava,
thus forming a number of shield volcanoes. Eventually, these eruptions shifted to what is
now 5 kilometers southwest of the modern volcano. Then, 610,000 years ago, the composition of magma
suddenly changed. It became far more siliceous, and as a result eruptions became more explosive.
When lava from this new magma chamber reached the surface, it erupted as trachyte lava, and formed
the beginnings of a much steeper stratovolcano. By 530,000 years ago, this volcanic cone stood at
2100 meters above sea level. After a 90,000 year long dormancy, eruptions at Paektu resumed ...but
this time at the base of the modern volcano. By 250,000 years ago, Paektu was 2400 meters tall.
As eruptions continued at the mountain, the resulting composition of rock indicated that
the magma chamber was changing at depth. Instead of erupting trachyte, the volcano began producing
a large amount of rhyolite lava. Rhyolite is an unusual type of lava to find at stratovolcanoes,
as its presence often indicates that a caldera can be found nearby. Then, 4000 years ago,
a section of the western summit collapsed in what is termed a lateral eruption. However,
this eruption would only pale in comparison to the next major eruption from the volcano.
Late in the winter of 946 AD, a massive eruption began on the 3600 meter high volcano.
During the initial phase of the eruption, the thick snow on Paektu melted, and cascaded down
the mountain thus forming a series of lahars. Over time, the eruption became more energetic.
Repeated pyroclastic flows raced down the slopes of the volcano into the surrounding plains.
At the same time, a vast area around Paektu and downwind to the east were
covered in a thick layer of white pumice. Then, the unthinkable happened. What was
previously a full magma chamber was now largely empty, and filled with air and volcanic gasses.
Due the weight of the above rock, a 5 kilometer wide section of the summit collapsed into the
ground, forming a vast caldera. From this caldera emerged a 36 kilometer high plume of ash, and a
pyroclastic flow which largely went eastward at more than 350 kilometers per hour. This
pyroclastic flow wiped out everything in its path, and traveled 85 kilometers before it stopped. As
ash reached high into the atmosphere, it fell across the majority of the Korean peninsula,
along with much of Japan, China, and Russia. This eruption, which lasted for approximately a week,
was at the time the largest eruption witnessed in human history. In total, 115 cubic kilometers
of tephra was ejected, and the height of the volcano was reduced by 850 meters.
However, this volcano was by no means dormant. In 1668, another large eruption took place,
which filled the much of the caldera rim and the surrounding landscape
with a layer of both lava and ash. In 1702, a smaller eruption occurred
on the southern edge of the caldera rim which created another pyroclastic flow.
Another eruption from this volcano took place at the eastern edge of the crater lake in 1903,
and formed a series of small explosion craters which were subsequently overlaid by lava.
Although no eruptions have since occurred from this volcano, it WILL erupt again.
The geologic record shows that this volcano erupts about once every 200 years. The volcano is
still clearly active due to ground deformation, changes in the temperature of the crater lake,
and active fumaroles in the region. Luckily, the next eruption from Paektu
will NOT form a new caldera. However, it could still be quite large. During the next eruption,
anyone within 20 kilometers of this mountain would need to be evacuated due to the threat
of both pyroclastic flows and lahars. I hope that you enjoyed this video. If
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