Okinawa again this year ~ 2024, AUG

Last year, during the Obon week, I rushed around the five of 100 Famous Castles and another 100 Famous Castles in Okinawa, but this year, without really thinking about what to do, I went to Cape Hedo, the northernmost point of Okinawa. I drove about 60km north from the Nago area where I was staying. From the cape, I could faintly see Yoron Island, 25km away. It's about 500-600km from here to Kagoshima, but I ended up right in the middle of the Nansei Islands, which stretch all the way to Taiwan.

When you come to Okinawa, you see a lot of limestone. You might say that it's natural that there is a lot of limestone (coral fossils) because it's a southern island, but the historical background of the north and south of the island is different. The recent Miyazaki earthquake has once again sounded the alarm about a major earthquake in the Nankai Trough, but basically it is the influence of the Philippine Sea Plate that is pushing the Japanese archipelago from below, and the Nansei Islands, including Okinawa, are at the same risk.

It is said that the formation of the Japanese archipelago began 30 million years ago, but what both the mainland and the islands of Okinawa have in common is a mixture of landmasses that originally belonged to the eastern edge of the Eurasian continent, strata carried by the Philippine Sea Plate, which is pushing in from the east, and strata formed locally in between. In the case of Okinawa, most of the limestone in the north is from the Mesozoic and Paleozoic eras (200 to 300 million years ago), which were carried from far away oceans and were detached when the Philippine Sea Plate subducted, and accumulated little by little as part of the landmass (called accretionary wedge). On the other hand, the limestone in the south is very new, having grown only a few hundred thousand years ago when the environment around Okinawa became suitable for coral growth. Coral can only grow in shallow, warm seas where sunlight reaches, and the so-called white Ryukyu limestone is the result of the southern part of Okinawa's main island becoming such an environment.

Among the castles (gusuku) I walked around last year, Nakijin Castle, located in the north, has a dark and hard stone wall, which is derived from the Paleozoic limestone mentioned above. Because it is hard and difficult to process, the castle is built using the rough-face construction method, in which stones of various sizes are skillfully combined and pebbles are sandwiched between them to ensure strength.

On the other hand, castles in the south can use white limestone, which is easy to work with, so their stone walls are made using a type of stone wall construction called "cloth masonry" or "partner masonry," which eliminates gaps where the stones meet.

The road to Cape Hedo runs along the coastline for a long time, and it is a journey that allows you to see the history of the earth while looking at rocks that have been carried by plates. Limestone is weak against acid rain, so it takes a long time to form various shapes, and although Akiyoshidai is amazing, this is also magnificent.

Daisekirinzan is a facility where you can walk through the karst plateau for a fee, and it seems that former Prime Minister Suga also visited it three years ago.

Last year, I was able to make the round trip safely by slipping through the gaps between typhoons, but this year, the return flight was canceled due to the sudden appearance of Typhoon No. 7, and I had to get off at Itami and stay overnight. Thanks to the cleverness of the injury, I was able to enjoy the Daigoji Temple National Treasure Exhibition at Nakanoshima Museum of Art at my leisure. There is a high risk of typhoons in Okinawa in the summer. Next time, I would like to change the season.