TheSeto Inland Sea (瀬戸内海,Seto Naikai), sometimes shortened to theInland Sea, is the body of water separatingHonshu,Shikoku, andKyushu, three of the four main islands ofJapan. It serves as awaterway connecting thePacific Ocean to theSea of Japan. It connects toOsaka Bay and provides a sea transport link to industrial centers in theKansai region, includingOsaka andKobe. Before the construction of theSan'yō Main Line, it was the main transportation link between Kansai and Kyūshū.
TheSetouchi region encompasses the sea and surrounding coastal areas. The region is known for its moderate climate, with a stable year-round temperature and relatively low rainfall levels. The sea experiences periodicred tides caused by dense groupings of certainphytoplankton that result in the death of large numbers of fish. Since the 1980s, the sea's northern and southern shores have been connected by the three routes of theHonshū–Shikoku Bridge Project, including theGreat Seto Bridge, which serves both railroad and automobile traffic.
On the West. The southeastern limit of the Japan Sea [InShimonoseki-kaikyo. A line running from Nagoya Saki (130°49'E) inKyûsû through the islands of Uma Sima and Muture Simia (33°58',5N) to Murasaki Hana (34°01'N) inHonsyû].
On the East (Kii Suidô). A line running from Takura Saki (34°16'N) in Honsyû to Oishi Hana in the island ofAwazi, through this island to Sio Saki (34°11'N) and on to Oiso Saki inSikoku.
On the South (Bungo Suidô). A line joining Sada Misaki (33°20'N) in Sikoku and Seki Saki in Kyûsyû.
The Seto Inland Sea is 450 km (280 mi) long from east to west. The width from south to north varies from 15 to 55 km (9.3 to 34.2 mi). In most places, the water is relatively shallow. The average depth is 38 metres (125 feet); the greatest depth is 105 metres (344 feet).[2]
Hydrologically, Seto Inland Sea is not a trueinland sea, being neither anepeiric body of water likeHudson Bay nor an isolatedendorheic basin like theCaspian Sea. Rather, it is actually amarginal sea: a division of a wider ocean (in this case the Pacific) which is partially enclosed by islands, archipelagos, or peninsulas (here, the Japanese Home Islands), adjacent to or widely open to the open ocean at the surface. TheNaruto Strait connects the eastern part of the Seto Inland Sea to theKii Channel, which in turn connects to the Pacific. The western part of the Seto Inland Sea connects to the Sea of Japan through theKanmon Straits and to the Pacific through theBungo Channel.
Each part of the Seto Inland Sea has a separate name in Japanese. For example,Iyo-nada (伊予灘) refers to the strait between Ehime, Yamaguchi, and Ōita prefectures in the western portion of the sea;Aki-nada (安芸灘) is the open expanse west of theGeiyo Islands, near Hiroshima prefecture; andSuō-nada (周防灘) refers to the expanse between Yamaguchi prefecture andSuō-Ōshima. These areas are sometimes styled Iyonada, Akinada, and Suonada. There are also many straits located between the major islands, as well as a number of smaller ones that pass between islands or connect the Seto Inland Sea to other seas or thePacific. Almost 3,000 islands are located in the Seto Inland Sea. The largest island isAwaji-shima, and the second largest isShōdo-shima. Many of the smaller islands are uninhabited.
Over 500 marine species are known to live in the Seto Inland Sea. Examples are theayu, anamphidromous fish,horseshoe crab,finless porpoise, andgreat white shark, which has occasionally attacked people in the Seto Inland Sea. In the past,whales entered the sea to feed or breed, however because ofwhaling and pollution, they are rarely seen.
During the lastice age, thesea level was lower than today. After the ice age, sea water poured into a basin between theChūgoku mountains andShikoku mountains and formed the Seto Inland Sea as it is known today. From ancient times, the Seto Inland Sea served as a main transport line between its coastal areas, including what is today theKansai region andKyushu. It was also a main transport line between Japan and other countries, including Korea and China. Even after the creation of major highways such as theNankaidō andSan'yōdō, the Seto Inland Sea remained a major transport route. There are records that some foreign emissaries from China and Korea sailed on the Seto Inland Sea.
The importance of water traffic gave rise to private navies in the region. In many documents, these navies were calledsuigun (水軍; "water army"), or simply pirates. Sometimes they were considered to be public enemies, but in most cases they were granted the right to self-governance as a result of their strength. During the feudal period,suigun seized power in most coastal areas. The Kono inIyo Province (todayEhime Prefecture) andKobayakawa (laterMōri) inAki Province (today a part ofHiroshima Prefecture) clans were two of the more famoussuigun lords. In the 12th century,Taira no Kiyomori planned to move the capital fromKyoto to the coastal village of Fukuhara (todayKobe) to promote trade between Japan and theSong dynasty of China. This transfer was unsuccessful, and soon after Kyoto became the capital again. Later, theBattle of Yashima took place off the coast of present-day Takamatsu.
In theEdo period, the Seto Inland Sea was one of the busiest transport lines in Japan. It was a part of a navigational route around Japan's islands via the Sea of Japan. Many ships navigated from its coastal areas to the area along the Sea of Japan. Major ports in the Edo period were Osaka, Sakai, Shimotsui,Ushimado, and Tomonoura. The Seto Inland Sea also served manydaimyōs in the western area of Japan as their route to and fromEdo, to fulfill their obligations undersankin-kōtai. Many used ships from Osaka. Thanks to transport through the Seto Inland Sea, Osaka became the economic center of Japan. Eachhan had an office calledOzakayashiki in Osaka. TheseOzakayashiki were among Japan's earliest forms of banks, facilitating domestic trade and helping to organize the income of thedaimyo, which was in the form ofkoku, giant bales of rice.
The Seto Inland Sea was also part of the official Chosendentsushi route, bringing Korean emissaries to the shogunate. After theMeiji Restoration, the coastal cities along the Seto Inland Sea were rapidly industrialized. One of the headquarters of theJapanese Navy was built in the town ofKure. Since the Meiji period, development of land transport has been reducing the importance of the Seto Inland Sea as a transport line. Remarkable land transportation innovations include theSan'yō Main Railroad Line in Honshū and theYosan Main Railroad Line in Shikoku (both completed beforeWorld War II) and three series of bridges connecting Honshū and Shikoku (completed in the late 20th century). The Seto Inland Sea is still used, however, by an international cargo transport line and several local transport lines connecting Honshū with Shikoku and Kyūshū.
Major cities with heavy industrial activity on the coast of the Seto Inland Sea include Osaka, Kobe, and Hiroshima. Smaller scale manufacturing and industry can also be found inKurashiki,Kure,Fukuyama, andUbe in Honshū, andSakaide,Imabari, andNiihama in Shikoku. Major industries includesteel production, vehicle manufacture, ship building, textiles, and since the 1960s, oil refining and chemical products.Imabari Shipbuilding, Japan's largest ship building company, has its headquarters and some of its yards inImabari, Ehime Prefecture. Thanks to the moderate climate and beautiful landscape, fishing, agriculture, and tourism bring a lot of income to the area as well.
Major highways in the Seto Inland Sea. Yellow: Kobe-Awaji-Naruto. Green: Seto-Ōhashi. Red:Nishiseto Expressway.KURE-MATSUYAMA ferry, Seto Inland Sea 2017
Today the Seto Inland Sea serves its coastal areas mainly for two purposes: first, international or domestic cargo transportation, and second, local transportation between coastal areas and islands on the sea. Major ports are Kobe, Okayama,Takamatsu, Tokushima, Matsuyama, and Hiroshima.
Historically, the Seto Inland Sea as transport line served four coastal areas: Kansai, Chūgoku, Shikoku, and eastern Kyūshū. The Seto Inland Sea provided each of these regions with local transportation and connected each region to the others and far areas, including the coastal area of the Sea of Japan, Korea, and China. After Kobe port was founded in 1868 to serve foreign ships, the Seto Inland Sea became a major international waterway with connection to the Pacific.
Development of land transportation shifted the travel between east and west — that is, between Honshū and Kyūshū — to railroad and road transport. Two coastal railways, San'yō Main Line in Honshū and Yosan Main Line, were built. Those railway lines stimulated the local economy and once invoked a rail mania. Many short railroads were planned to connect a certain station of those two lines and a local seaport on the Seto Inland Sea, and some of them were actually built. The Ministry of Railroads, later theJapanese National Railways and thenShikoku Railway Company, ran some train ferry lines between Honshū and Shikoku including the line between Uno Station (Tamano) andTakamatsu Station (Takamatsu). When theGreat Seto Bridge was finished and began to serve the two coastal areas, that ferry line was abolished.
The Great Seto Bridge connects Okayama Prefecture with Kagawa Prefecture since 1988. It consists of a total of six two-storey bridges, whose lower floors are used by the railway (Japan Railways Group). The high speedShinkansen does not go to or on Shikoku.
This is the first of three intersections of the Seto Inland Sea. Construction started in 1975, but was fully completed in 1999. It connects the Nishiseto-Onomichi Highway in Hiroshima Prefecture with a total of ten bridges and several smaller islands with Imabari inEhime Prefecture. Approximately 100,000 people live on those islands. The bridges are: Shin Onomichi Bridge,Innoshima Bridge, Ikuchi Bridge,Tatara Bridge, Ōmishima Bridge, the two Ōshima bridges and the three Kurushima Kaikyo bridges. TheKurushima Kaikyō Bridge connects the island ofŌshima to the main island ofShikoku.
Seto Naikai Pilots Area provides compulsorymaritime piloting for vessels over 10,000 tones, it was divided into sections of Bisanseto and sections ofKurushima, connectingKanmon Channel Piloting Area andOsaka Bay Piloting Area.[3][4]
The coastal area of the Seto Inland Sea is one Japan's major tourist destinations. Even before the country opened to foreigners in the middle of the 19th century, the sea's beauty was praised and introduced to the Western world by those who visited Japan, includingPhilipp Franz von Siebold, and after the country's opening,Ferdinand von Richthofen andThomas Cook.
Itsukushima Shrine, on the island ofItsukushima in the city ofHatsukaichi, is a UNESCOWorld Heritage Site.Shōdoshima, nicknamed the "island of olives", and theNaruto whirlpools are two other well-known tourist sites. Neighboring locations likeKotohira andOkayama are often combined with the tour of the Setouchi region. Some historic sites, including Yashima inTakamatsu andKurashiki, also attract many visitors.Hiroshima is the neighbor city to Itsukushima Shrine and another UNESCO World Heritage Site because ofatomic bomb damage in 1945. Idol UnitSTU48 operate on a cruise on the Setuchi.
The eastern end of the Sea hosts theSetouchi Triennale art festival, which was inaugurated in 2010. Some events take place on the island ofNaoshima, known colloquially as the art island, and the home of several permanent museums.
At the far eastern extremity, as the Sea meets the Pacific Ocean, are theNaruto whirlpools that can be reached by sight-seeing boats.
TheShiwaku Islands are a defined group numbering 28 that can be reached by ferry boat fromMarugame. HereRichard Henry Brunton built one of his lighthouses that can still be seen, and the grave ofFrank Toovey Lake, a young midshipman in his survey party, is on the island of Sanuki Hiroshima.
In the central area of Seto Inland Sea isMount Ishizuchi onShikoku. It is the highest mountain in western Japan and the highest mountain onShikoku.
Some sites along the Seto Inland Sea were featured in eighth-century Japanese literature, both in prose and in verse, includingKojiki,Nihon Shoki, andMan'yōshū. Since some sites were used as places of exile, their feeling and landscape were evoked inwaka. In fiction, inThe Tale of Genji, Genji fled from Kyoto and resided in Suma (now a part ofKobe) andAkashi for two years.
In medieval literature, because of theGenpei War, the Seto Inland Sea is one of the important backgrounds ofThe Tale of the Heike, particularly in its latter part.
In the Western world,Donald Richie wrote a literary nonfiction travelogue calledThe Inland Sea relating a journey along the sea, beginning from the East at Himeji and ending at Miyajima in the West, close to Hiroshima, going from island to island, exploring the landscape, meeting and discussing with local people, as well as musing on Japanese culture, the nature of travel and of identity, and his own personal sense of identity.In 1991, filmmakersLucille Carra and Brian Cotnoir produced a film version of Richie's book, which further explored the region through interviews and images photographed by Hiro Narita. Produced by Travelfilm Company and adapted by Carra, the film won numerous awards, including Best Documentary at the Hawaii International Film Festival (1991) and the Earthwatch Film Award. It screened at the Sundance Film Festival in 1992.[5]
A critical plot element of the Japanese seriesFafner in the Azure is an alien life form discovered at the bottom of this sea known as the Seto Inland Sea Mir.
