Japan has a total of 6,852 islands extending along the Pacific coast of East Asia. The country, including all of the islands it controls, lies between latitudes 24° and 46°N, and longitudes 122° and 146°E. The main islands, from north to south, are Hokkaido, Honshu, Shikoku and Kyushu. The Ryukyu Islands, which include Okinawa, are a chain to the south of Kyushu. Together they are often known as the Japanese archipelago.
About 73 percent of Japan is forested, mountainous and unsuitable for agricultural, industrial or residential use.] As a result, the habitable zones, mainly located in coastal areas, have extremely high population densities. Japan is one of the most densely populated countries in the world.
The islands of Japan are located in a volcanic zone on the Pacific Ring of Fire. They are primarily the result of large oceanic movements occurring over hundreds of millions of years from the mid-Silurian to the Pleistocene as a result of the subduction of the Philippine Sea Plate beneath the continental Amurian Plate and Okinawa Plate to the south, and subduction of the Pacific Plate under the Okhotsk Plate to the north. The Boso Triple Junction off the coast of Japan is a triple junction where the North American Plate, the Pacific Plate and the Philippine Sea Plate meets. Japan was originally attached to the eastern coast of the Eurasian continent. The subducting plates pulled Japan eastward, opening the Sea of Japan around 15 million years ago.
Japan has 108 active volcanoes. During the twentieth century several new volcanoes emerged, including Shōwa-shinzan on Hokkaido and Myōjin-shō off the Bayonnaise Rocks in the Pacific. Destructive earthquakes, often resulting in tsunami, occur several times each century. The 1923 Tokyo earthquake killed over 140,000 people. More recent major quakes are the 1995 Great Hanshin earthquake and the 2011 Tōhoku earthquake, a 9.1-magnitude quake which hit Japan on March 11, 2011, and triggered a large tsunami. Japan is substantially prone to earthquakes, tsunami and volcanoes due to its location along the Pacific Ring of Fire. It has the 15th highest natural disaster risk as measured in the 2013 World Risk Index.