It remained unnoticed until local fishermen investigated.

This fall, Esanbe Hamakita Kojima, a tiny island off the northeast coast of Japan dropped out of sight. The island’s disappearance went unnoticed by inhabitants of the nearby village of Sarufutsu, situated on the northern tip of Hokkaido island only 1,640 feet away.

It wasn’t until September, when author Hiroshi Shimizu traveled to Sarufutsu to gather inspiration for his picture book on Japan’s islands, that authorities were notified of the island’s disappearance. Shimizu had been looking for the island but couldn’t locate it. He informed local fisherman who went out to investigate and finally noted that Esanbe was missing.

When Japan’s Coast Guard last surveyed the island in 1987, it was only 4.5 feet above sea level. Authorities could not confirm how large the island had been before the sea rose around it.

Esanbe is west of Japan’s Northern Territories and part of a set of islands that has been long-contested between Japan and Russia. The islands, called the Kurils by Russia, were taken by the Soviets shortly after World War II, but ownership today remains unclear. According to CNN, Esanbe functions as a marker of Japanese ownership in contested waters. But the strategy of claiming islands to maintain the maritime space around them is not exclusive to Esanbe. In fact, according to the Washington Post, Japan owns 158 uninhabited islands that the country named in 2014 so that the sea surrounding them could remain in Japanese control.

Thus, the disappearance of the island may have a slight effect on Japan’s territorial waters, as according to international law, countries can only claim ownership of the sea around an island if that island is visible at high tide. Coast Guard officials in Japan confirmed that Esanbe’s loss, “may affect Japan's territorial waters a tiny bit.” With the island underwater, Japan will have lost approximately 1,640 feet of territorial water.

The island’s disappearance was likely due to erosion by the wind and drift ice common in the Sea of Okhotsk each winter. According to coast guard official Tomoo Fujii, “There is a possibility that the islet has been eroded by wind and snow and, as a result, disappeared,” Asahi Shimbun of the Japanese Daily reported.

According to the Smithsonian, disappearances of land masses in this area of Japan are not unlikely. The good news for Japan’s border, however, is that this phenomenon can occur in reverse. Five years ago, a 1000-foot long island rose out of the sea, prompted by a landslide.

EMMA BRUCE is an undergraduate student studying English and marketing at Emerson College in Boston. While not writing she explores the nearest museums, reads poetry, and takes classes at her local dance studio. She is passionate about sustainable travel and can't wait to see where life will take her.