British researchers unlocking secrets of North Korea volcano, site of huge ancient eruption
More than a thousand years ago, a huge volcano straddling the border between North Korea and China was the site of one of the biggest eruptions in human history, blanketing eastern Asia in its ash.Full Story
“Geologist [I'm Climate Change]”
Since: Mar 07
#1 Sep 3, 2014
Interesting, still have to wade through the spam, but eventually got back to the comments box.
The Baitoushan volcano is actually a backarc basin volcano if the Ryukyu arc, which is a giant backarc basin apparently spreading as a result of rifting associated with the Hainan hotspot.
It appears @ Korea as a result of the Korean and Sikhote-Alin margin being an end stop up against the compressing sea of japan backarc basin, which is more compressed than the Ryukyu backarc basin.
Magma filled fractures in the deep crust filled during crustal relaxation in rare tsunamigenic earthquakes @ the Ryukyu arc are squeezed E as a result of differential recompression rates of the decsending plate (the philippine sea plate). The result is that in the backarc region a backarc rift arrives at Halla (south Korea), several pleistocene shields along the Korean spine, a main rift fracture (Baitoushan) and a backarc cinder cone & maar field in SE china close to the Russian border & the Sikhote-Alin volcanic field on the mainland near southern Sakhalin.
Baitoushan is a big volcano because it occupies a backarc rift & receives long fractures full of backarc basin magma (alkali basalt & its differentiates), during each crustal relaxation & recompression cycle. It appears to be a much bigger volume than Halla & is probably older. The current rift in the arc of the Ryukyu backarc basin appears to be about 2 million years old which is younger than the inception dates of Baitoushan & Halla.
Crustal relaxation & bloody great big tsunami @ Ryukyu backarc basin appear to be very rare events with a huge recompression interval time. The most compressed bit appears to be near Taiwan, where the convergence rate is fastest. It is currently in the late stage but the descending plate is still descending, so there are several decades to go before the megathrust lets go. There is evidence of one prior tsunami about 4000-5000Bp but this event may be a major teletsunami from the Philippines trench. It is evidenced by the breakage of a barrier beach bar & erosion of a bog before the bar reformed & the bog re sedimented (lost sediment horizon), and also in the filling of Wakamiko caldera (Aira near kagoshima) with marine sediment (undated but quite old due to hydrothermal activity in the crater fill screwing up 14c dating of core samples).
The big long fracture has already squeezed into Baitoushan (see article for result), but there are thinner sub parallel fractures squeezing in along the old fracture set (still hot), hence unrest @ the volcano right about now, and also the post caldera eruptive history.
Will also show up an eruption series @ Baitoushan if the work goes properly, with an average of 7000 to 10,000 years or so between really big events @ the volcano.
happy hunting, & try not to be sidetracked into breaking rocks in other parts of N. Korea!
have a nice day: Ag
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