The Baltic Sea (Mare Balticum) was named by German chronicler Adam of Bremen in the 11th century, possibly from the Latin equivalent ("balteus"). The belt reference applies to the manner in which the Baltic Sea waters stretch through the land. In the Middle Ages, the sea was known by many different names; it was only in the 16th century that the name "Baltic Sea" became prevalent.
In the early Middle Ages, the boundaries of the Baltic Sea were the trade sites of Scandinavian Vikings. Battles with Wendish tribes (Slavic people originating from the Baltic Sea's southern coast) for control of the sea followed, with the Vikings dominating.
In the 12th century, Slavic piracy intensified before Denmark eventually took control over the majority of the sea's coastlines. During the subsequent centuries, through many wars, control of the Baltic Sea has passed between Sweden, Germany, Russia and Poland.
The periphery of the Baltic Sea is made up of the coastlines of Denmark, Sweden, Finland, Russia, Estonia, Latvia, Lithuania, Poland and Germany. The northernmost area is called Bothnian Bay. The Northern Baltic Sea lies between the Stockholm area of Sweden, Estonia and southwestern Finland. The Bay of Kiel is the westernmost part of the Baltic Sea. The three Danish straits (the Great Belt, the Little Belt and The Sound) link the Baltic Sea to the North Sea's Kattegat Bay and Skagerrak strait.
The Baltic Sea is around 1,000 miles long, 120 miles wide, and has an average depth of 180 feet. The maximum depth is 1,506 feet on the Swedish side. The surface area of the Baltic Sea is approximately 145,522 square miles and its volume is approximately 5,040 cubic miles. The coastline circumference measures around 4,968 miles. During winter months, approximately half of the Baltic Sea's surface is completely iced.
Extensive 20th century industrialization of the countries bordering the Baltic Sea has led to an enormous decline in the sea's wildlife. Many of its species are endangered, such as the gray seal of the Baltic, but major conservation work is ongoing to protect these and other creatures of the Baltic Sea. The mute swan (Cygnus olor) is the largest bird found in the Baltic. Porpoises and dolphins can be found in the Danish waters of the Baltic Sea.
