ナショナルジオグラフィックのインスタグラム(natgeo) - 11月29日 19時49分

Photo by @shonephoto (Robbie Shone) - Clearwater Cave in Gunung Mulu National Park, Malaysia, is currently recorded as the 8th longest cave in the world. This enormous cave system, which has many levels of passages at different elevations, has developed over millions of years. The highest levels are the oldest ones, and have long since been abandoned by the underground river that carved them out. Photographed here is the youngest and lowest level, which is being formed and modified by the present day river level. The large notch that is seen on both the left and right hand side of the passage formed when an impenetrable bed lay at the base of the river, preventing it from cutting downwards and causing the river to cut sideways instead. As the climate changed, so did the input to the cave system, and the impenetrable bed was removed allowing the river to once again cut down into the limestone.

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