Geohistory - Terrain
Rōsoku-jima (Candle Island) is a strangely-shaped rock standing in the sea northwest of Dōgo Island. From a sightseeing boat, a truly breathtaking sight can be seen at the moment the setting sun lights up the tip of the island.
Rōsoku-jima and the surrounding rocky terrain are made up of trachyte, lava that erupted about 5.5 million years ago. The island was not always an island; it was once part of a cape extending from Dōgo Island. The surrounding area was worn away by waves, and the island became a sea stack as we see it today.
The reason this unusual candle-like shape was able to form is because of the cracks hidden in the rock. These vertical cracks are called columnar joints, and were formed when the lava cooled and solidified. As the wind and waves erode away at the rock, it naturally breaks off along these cracks, which is how this shape formed.
