Jeju Island Geology, for a start

I have been enjoying living on an island. It is perhaps the exact opposite, geographically, from living in the middle of Iowa. Jeju Island was formed by a volcano-- similar to the Hawaiian island. The volcano, Halla-san (san means mountain in Korean), stands tall in the center of the island, almost always shrouded in humidity and clouds, sometimes poking its head out above them. I have only seen the whole thing clearly once so far. My co-teacher says that it is usually only visible for 10 days a year, or that's what people say.

There are scattered around the island about 360 "parasitic" volcanic cones-- that means that for at least part of the time that Halla-san was active, the amount of magma underneath it was so great that the main volcano was not big enough to release it and it pushed its way through all over the place. The small peaks are visible all over the place-- in Jeju's dialect of Korean they are called "oreum." I have climbed a couple so far, and I love to see them in the distance and imagine the lava shooting out and pooling over the landscape. This would have been a truly dramatic place to live a few hundred thousand years ago.

There are remnants of Jeju's dramatic past all over: the sharp divide between land and see, sometimes dropping off from basalt cliffs to deep water; the oreum scattered across the island, sometimes with their feet in the water; and the lava tubes. Christian and I visited one lava tube called Manjang cave.
I wasn't able to get a good shot with my camera, so here's one from Discover Korea.

It is a place where lava pushed through-- perhaps taking advantage of a crack in the rock--  the outer layer of lava solidified and the rest kept flowing. This picture is of the end of the tunnel that is open to tourists (Manjang cave being one of two or three sections of tunnel open anywhere on the island, out of I think 5 or 6 known tunnels-- one of which is more than 13km long). As we were leaving, I noticed that a lot of the ceiling had light patches. I wondered what they were, and Christian suggested that they might be minerals leached from the soil above. I said, naahh, that's possible, I guess, but highly improbable. Well, one of the first sentences in the UNEP report is that that is exactly what happened, and that is it rare. So, I feel silly, but not completely silly?

It's a beautiful place! Come visit!

--Pretty much all of the information in this post that isn't a personal anecdote is from the United Nations Environmental Project Report on Jeju island as a World Heritage Site, which you can download for your very own self! It's only about 6 pages long, and chock-full of great information.

--also, please note that each of these 'exploring the world' and china series posts are labeled as such, and the tags are at the top of the list on the righthand side of this page. If you just want to view one of these series, just click on its label!