Rebun Island lies in the Sea of Japan off the northwestern tip of Hokkaido and is part of the Rishiri-Rebun-Sarobetsu National Park. Momoiwa ("Peach Rock") was created in a relatively new era of Rebun Island's strata when underground magma pushed the earth's surface upward where it cooled into a huge spherical rock formation. Spheroidal joints (plate-shaped joints on the surface) peeled away like the skin of an onion, revealing the scree, which cooled at a slower rate than the surface, creating the columnar jointing that can be seen.
<a href="//commons.wikimedia.org/wiki/User:OKJaguar" title="User:OKJaguar">OKJaguar</a>
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<span class="int-own-work" lang="en">Own work</span>