Volcano lava icecavern, formed mainly because of the different solidifying velocities between surface lava and bottom lava.
火山熔岩冰洞，是由于表层熔岩和底层熔岩的凝固速度不一样而形成。
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Five-hour glacier treks bring you up close and personal to the glacier's myriad peaks, fissures and, if you're lucky, the icecavern the lake hollows underneath, all effusing an ethereal blue glow.