Мраморное море: География, история и экологические проблемы.

Sea between the Mediterranean and Black seas

The Sea of Marmara, also known as the Sea of Marmora or the Marmara Sea, is a small inland sea located entirely within the borders of Turkey. It connects the Black Sea to the Aegean Sea via the Bosporus and Dardanelles straits, separating Turkey’s European and Asian sides. It has an area of , and its dimensions are Its greatest depth is .

The Sea of Marmara is named after the largest island on its south side, called Marmara Island because it is rich in marble (Greek μάρμᾰρον (mármaron) "marble"). In classical antiquity, it was known as the Propontis, from the Greek words pro (before) and pontos (sea), reflecting the fact that the Ancient Greeks used to sail through it to reach the Black Sea, which they called Pontos.

In Greek mythology, a storm on the Propontis brought the Argonauts back to an island they had left, precipitating a battle in which either Jason or Heracles killed King Cyzicus, who had mistaken them for his Pelasgian enemies.

There are two main groups of islands in the Sea of Marmara. To the north lie the Princes' Islands, an archipelago made up of the inhabited islands of Kınaliada, Burgazada, Heybeliada, Büyüyada and Sedef Adası and several uninhabited islands including Sivriada, Yassıada, Kaşıkadası and Tavşanadası. The inhabited islands are readily accessible by ferry from both the European and Asian shores of İstanbul and the entire archipelago forms part of the conurbation. To the south lie the Marmara Islands, an archipelago made up of the eponymous Marmara Island and three other inhabited islands – Avşa, Paşalimanı and Ekinlik – as well as of seventeen largely uninhabited islands including the prison island of Imralı whose most famous prisoner, since 1999, has been the PKK leader Abdullah Öcalan. These islands lie within Balıkesir province and are most readily accessible from Tekirdağ in Thrace or Erdek on the southern shore of the Sea of Marmara. In high summer additional ferries travel to Avşa and Marmara Islands from the centre of İstanbul to facilitate a growing tourist trade. There are also a few individual islands elsewhere in the Sea of Marmara, such as Koç Adası, off Tuzla, which is privately owned by the Koç family of industrialists.

The North Anatolian Fault runs under the sea and has triggered several major earthquakes, such as those in Izmit and Düzce in August and November 1999 respectively. The August 1999 earthquake is commonly referred to as the Marmara Earthquake since its epicentre lay under the Sea and most of the places worst affected by the quake and ensuing tsunami lay along its shores. During a storm on 29 December 1999, the Russian oil tanker Volgoneft broke in two in the Sea of Marmara, spilling more than 1,500 tonnes of oil into the water. In 2021 the shores of the Sea of Marmara were disfigured by marine mucilage nicknamed 'sea snot' caused, at least in part, by the dumping of untreated waste into the water.