Onega Bay Onega Bay The Onega Bay () is located in the Republic of Karelia and Arkhangelsk Oblast in Northwestern Russia, west of the city of Arkhangelsk. It is the southernmost of four large bays and gulfs of the White Sea, the others being the Dvina Bay, the Mezen Bay, and the Kandalaksha Gulf. The area of the bay is . The Onega Bay is long and - wide. The average depth of the bay is , and the maximum depth is . The bay freezes in winter. Onega, Kem, and Vyg Rivers flow into the bay. The bay has numerous islands.
Lake Onega the last Ice Age, about 12,000 years ago: In the Paleozoic Era (400–300 million years ago) the entire territory of the modern basin of the lake was covered with a shelf sea lying near the ancient, near-equatoric Baltic continent. Sediments at that time – sandstone, sand, clay and limestone – form a layer covering the Baltic Shield which consists of granite, gneiss and greenstone. The retreat of the Ice Age glaciers formed the Littorina Sea. Its level was first higher than at present, but it gradually lowered, thereby decreasing the sea area and forming several lakes in the Baltic region.