Japanese archipelago

The Japanese archipelago includes four major islands and many smaller ones, stretching roughly 1500 miles[1] from Hokkaidô in the north, to the Ryûkyû Islands in the south.[2] The four main islands of Hokkaidô, Honshû, Shikoku, and Kyushu cover a total of roughly 146,000 square miles or 378,000 square kilometers.[1][3]

The islands lie at the intersections of four tectonic plates[4], have volcanic origins, and are heavily mountainous.[5] The islands are home to over sixty active volcanoes, comprising roughly ten percent of the active volcanoes in the world, and including several of the archipelago's most famous mountains.[6] Sakurajima in southern Kyushu has erupted more or less constantly since 1950; Mt. Fuji is also considered active, though it has not erupted since 1708. The islands are also one of the chief centers of earthquake activity in the world.

Japan's land is relatively new, in geologic time, as compared to many other areas of the world, with its mountains forming only about two to three million years ago. With roughly 80% of the archipelago consisting of mountainous bedrock, and grasslands terminating sharply at steep mountain rises,[6] only about 13 percent of the islands' land area is left as fertile plains.[1] While much land was reclaimed during the Edo period, significantly expanding the total amount of land under cultivation, this could only go so far, and eventually hit up against strict topographical environmental limits.

A considerable portion of the country's population, and political, cultural, and agricultural activity are concentrated in these limited areas of cultivable plains. The four most historically significant areas of fertile plains are the Tsukushi Plain in northwest Kyushu (centered on the city of Kurume, and stretching north to include Fukuoka/Hakata), the Kinai Plain (in which are situated the cities of Nara, Kyoto, and Osaka), the Nôbi Plain (in which Nagoya is located, and stretching south to Ise Bay), and the Kantô Plain (home to Tokyo and an extensive surrounding area). Despite its geologic youth, however, Japan's proximity to the Asian continent has allowed it to develop considerable biodiversity; Japan is home to around 500 indigenous trees, as compared to around eighty in western Europe, or 250 in North America.[6]


During winter, the prevailing winds are from the continent, bringing cold air east to Japan's western (Sea of Japan) coast. Moisture from the Sea of Japan falls chiefly on areas to the north and west of the major mountain ranges (e.g. the Hokuriku region, including the modern-day prefectures of Niigata and Ishikawa, among others), while those areas to the south and east, i.e. on the Pacific Ocean side of the mountains (including Tokyo, the Kinai, and many other regions) experience far drier winters.

In summer, warm, moist winds come up from the south, bringing a rainy season towards the beginning of the summer, and, in many areas, oppressively hot and humid conditions beyond what might be expected for the latitude, given that all of Japan (with the exception of the Ryukyus, i.e. Okinawa prefecture) lies officially within the temperate zone. These conditions bring typhoons, which threaten chiefly the Ryukyus up through the southern and eastern coasts of Kyushu and Shikoku, but the wet conditions also make this southern & eastern side of the mountains more conducive to greater agricultural yields.

The famous Kuroshio current, a warm jetstream which brings warm water up from the tropics, contributes to this effect, while the Oyashio current brings nutrient-rich cold water down from Hokkaidô into the waters surrounding the Tôhoku region (the northeastern end of Honshû).


  • Conrad Shirokauer, Suzanne Gay, and David Lurie, A Brief History of Japanese Civilization, Wadsworth Cengage Learning (2013), 3-5.
  1. 1.0 1.1 1.2 Shirokauer, et al., 3-5.
  2. The northernmost parts of Hokkaidô lie at 45 degrees North latitude, and the southern portions of Kyushu, i.e. the southernmost points in the Japanese "mainland," around 31 degrees North. Yonaguni Island, one of the southernmost of the Ryûkyû Islands, lies at around 24 degrees North.
  3. The land area of the three main islands which formed the extent of the realm throughout its pre-modern history, i.e. excluding Hokkaidô and the Ryukyus obtained in the late 19th century, is around 114,000 square miles, or 295,000 km2.
  4. The North American, Eurasian, Pacific, and Philippine Sea plates.
  5. That is, with the exception of the Ryûkyû Island chain, which is relatively flat, close to sea level, and is composed chiefly not of volcanic soil, but of limestone, deriving from coral origins.
  6. 6.0 6.1 6.2 Conrad Totman, Early Modern Japan, University of California Press (1993), 4-5.