The engineering-geological position reveals the peculiarities of structure and physical-mechanical properties of bottom soil of the Barents and Kara seas. Consider the conditions for the formation of the latest sediments, their relationship with the repeated freezing and defrosting during the late Cenozoic, the peculiarities of polar lithogenesis. Regional factors of variability and features of variability of the physical-mechanical properties of bottom soil with depth are shown. Conclusions are made about the ambiguous influence of the historical-geological factors on physical-mechanical properties of soils. The role of soils, containing submarine gas hydrates, is shown.