Tatami-ishi (畳石, “tatami stones”) is a geological feature in Kumejima, Okinawa, Japan. The Tatami-ishi is a series of more than 1,000 pentagonal and hexagonal rocks that are arranged in a regular pattern on the beach. The rocks are one to two meters in diameter and are made of andesite, a type of volcanic rock.

The Tatami-ishi was formed by a process called columnar jointing. This occurs when lava cools and contracts very rapidly, forming vertical cracks in the rock. The cracks are typically hexagonal or pentagonal in shape, and they are evenly spaced.

The Tatami-ishi is thought to have formed about 20,000 years ago when a lava flow from a nearby volcano cooled rapidly. The lava flow was thick and slow-moving, which allowed it to cool evenly and form a regular pattern of cracks.

The Tatami-ishi is a popular tourist destination, and they are often featured in Japanese art and literature. They are a unique and beautiful natural phenomenon that is a testament to the power of nature.

In addition to their natural beauty, the Tatami-ishi is also of scientific interest. They provide insights into the processes of lava cooling and columnar jointing. The Tatami-ishi is also a valuable resource for studying the geology of Okinawa Island.

According to the Internet