Dvina Bay streams. There are many small islands in the Dvina Bay as well, the biggest being Mudyug Island. A national park, Onezhskoye Pomorye National Park, was open on the Onega Peninsula on 26 February 2013. The Dvina Bay is limited by the Onega Peninsula from the west. At the eastern side, the shore steeply rises to a plateau (White Sea - Kuloy Plateau) which drains east into the Soyana, a major tributary of the Kuloy. The Onega Bay shore is often referred to as "Letny Bereg" (Summer Coast), and the eastern shore of the bay is "Zimny Bereg" (Winter Coast). The
Arkhangelsk Oblast and the non-freezing harbour of Murmansk, lost its significance as the main trading harbour of the Russian Empire. However, in the early 20th century Arkhangelsk was an important starting point for Russian Arctic expeditions. For instance, in the 1830s Pyotr Pakhtusov sailed twice from Arkhangelsk to investigate and map Novaya Zemlya. In 1932 the "Icebreaker Sibiryakov" under the command of Vladimir Voronin, sailing from Arkhangelsk, crossed the Northern Sea Route in a single navigation. In 1918 and 1919, Arkhangelsk Governorate became one of the most active battlegrounds of the Civil War in Russia. On August 2, 1918, Arkhangelsk was occupied