Columnar Basalt on Jeju Island, Korea
• My recent junket to South Korea, purportedly on the invitation of the International Plant Biology conference, took me to Jeju Island. Dominated by the central Halla-san volcano, this temperate island has waterfalls plunging into the glittering ocean, skates drying in the wind, and tangerine groves galore. I spotted these geological formations of columnar basalt along the southern coast of Jeju island at Jusangjeolli (주상절리), and at the three-tiered Cheonjeyeon Waterfall.
• Basalt is volcanic rock formed from cooling lava. As thick lava flow cools, it fractures- more easily in the horizontal direction than vertical. This results in columnar basalt, with amazingly regular hexagonal shapes. The slower the cooling, the larger the columns. The ones on Jeju-do were formed between 250,000 and 140,000 years ago, during the Pleistocene period. Another famous example is the Giant’s Causeway of Ireland, where the geometric perfection seems artificial or photoshopped!
Thanks to Thomas Kang for exhorting me to check these out. HIRL account with Thomas coming up; sorry, no pictures of the Korean spa 😉