5. Jeju Island is a volcanic island that is a UNESCO World Heritage site because of its cave system that came into existence through which related process?
From Quiz Jeju D'oh
Answer:
Lava tube formation
Most caves around the world are formed over thousands, if not millions, of years through water erosion of limestone but the caves on Jeju Island were formed by volcanic activity that led to lava tubes. Interestingly, these tubes then began to exhibit normal cave life with limestone structures being formed in them. This makes these caves unique from caves found anywhere else on earth.
The Geomunoreum Lava Tube System is "regarded as the finest such cave system in the world", according to the UNESCO website. Numerous caves and tubes have been discovered so far with some being designated as natural monuments. Examples are the Bukoreumdonggul Lava Tube, Mangjanggul Lava Tube, and Dangcheomuldonggul Lava Tube. The Mangjanggul Lava Tube, The Hyeopjaegul Lava Tube, the Ssangyonggul Cave, the Seonheulli Bengdwigul Cave, and the Gimnyeongsagul Cave are all open to the public for tours. Visible in these caves are stalactites, stalagmites, and stone pillars.
This question was rappelled into the quiz by Phoenix Rising's resident spelunking enthusiast tazman6619.