Iceland is a Nordic island country between the Arctic Ocean and the North Atlantic Ocean, located on the Mid-Atlantic Ridge between Europe and North America. It is culturally and politically linked with Europe and is the region's westernmost and most sparsely populated country. Its capital and largest city is Reykjavík, which is home to about 36% of the country's roughly 390,000 residents (excluding nearby towns/suburbs, which are separate municipalities). The official language of the country is Icelandic. Iceland is on a rift between tectonic plates, and its geologic activity includes geysers and frequent volcanic eruptions. The interior consists of a volcanic plateau with sand and lava fields, mountains and glaciers, and many glacial rivers flow to the sea through the lowlands. Iceland is warmed by the Gulf Stream and has a temperate climate, despite being at a latitude just south of the Arctic Circle. Its latitude and marine influence keep summers chilly, and most of its islands have a polar climate. According to the Landnámabók, an ancient manuscript, the settlement of Iceland began in 874 AD, when the Norwegian chieftain Ingólfr Arnarson became the island's first permanent settler. In following centuries, Norwegians and to a lesser extent other Scandinavians, immigrated to Iceland, bringing with them thralls (i.e., slaves or serfs) of Gaelic origin.