Seto Inland Sea

The Seto Inland Sea is a vital body of water in Japan.

It separates three of the four main Japanese islands: Honshu, Shikoku, and Kyushu. This sea serves as a major waterway. It connects the Pacific Ocean to the Sea of Japan. It also links to Osaka Bay. This connection provides a sea transport link to industrial centers. These include cities like Osaka and Kobe in the Kansai region. The surrounding coastal areas are known as the Setouchi region.

Geographically, the Seto Inland Sea is a marginal sea. A marginal sea is a division of a wider ocean. It is partially enclosed by islands or peninsulas. In this case, the Japanese Home Islands enclose the water. It is not an epeiric body of water like Hudson Bay. It is also not an isolated endorheic basin like the Caspian Sea. The Naruto Strait connects the eastern part to the Kii Channel. This channel then leads to the Pacific Ocean. The western part connects to the Sea of Japan via the Kanmon Straits. It also connects to the Pacific through the Bungo Channel.

The sea is quite long from east to west. Its width from south to north varies. Most areas of the sea are relatively shallow. The average depth is 38 meters. The greatest depth is 115 meters. Almost 3,000 islands are located within the sea. Awaji-shima is the largest island. Shōdo-shima is the second largest island. Many of the smaller islands are uninhabited. The sea contains many straits between major islands. Some areas have specific names. For example, the Iyonada is a part of the sea. Other areas include the Akinada and the Suonada.

The history of the sea began after the last ice age. During that time, the sea level was lower. After the ice age, water filled a basin. This basin sat between the Chūgoku and Shikoku mountains. This process formed the sea we see today. Since ancient times, the sea has been a main transport line. It linked coastal areas to each other. It also linked Japan to Korea and China. Powerful sea groups called suigun once controlled the coast. These groups were sometimes called pirates. They were very strong and often had the right to self-governance.

In the Edo period, the sea was very busy. It was a major part of a navigational route around Japan. Many ships moved from the coast to the Sea of Japan. Major ports included Osaka, Sakai, Shimotsui, Ushimado, and Tomonoura. This transport helped Osaka become an economic center. Many daimyōs used the sea to travel to Edo. They did this to fulfill obligations known as sankin-kōtai. This trade helped organize the income of the daimyo. This income often came in the form of koku, which were large bales of rice.

Today, the sea supports many industries.

Major cities like Osaka, Kobe, and Hiroshima have heavy industrial activity. Coastal cities also include Kurashiki, Kure, and Fukuyama. Industries include steel production and vehicle manufacture. Many areas focus on shipbuilding and textiles. Since the 1960s, oil refining and chemical products have also grown. Imabari is home to Japan's largest shipbuilding company. The Setouchi region also relies on fishing and tourism. This is due to the moderate climate and beautiful landscape.

Land transport has changed how people move.

In the late 20th century, the Honshū–Shikoku Bridge Project was completed. This project connected the northern and southern shores. The Akashi Kaikyō Bridge is one of the routes. It is the second-longest suspension bridge in the world.

Another route is the Great Seto Bridge. This bridge carries both automobile and railroad traffic. There is also the Nishiseto Expressway. This connects Hiroshima to Imabari through ten bridges. These bridges have made travel much faster than old ferry lines.

However, the sea is still used for international cargo. It remains a vital link for local transport between islands.