White Sea small. The main island group is the Solovetsky Islands, located almost in the middle of the sea, near the entrance to Onega Bay. Kiy Island in Onega Bay is significant due to a historic monastery. Velikiy Island, located close to the shore, is the largest island in the Kandalaksha Gulf. The White Sea is a water-filled depression in the block of a continental shelf known as the Baltic Shield. Its bottom is very uneven and contains the Kandalaksha Hollow in the northwest and the Solovetsky Islands in the south. Also, the Onega Bay has many small underwater elevations. The opening
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