The term 'Siberian Expanse' refers to the vast area of land in Siberia, which is made up of two distinct geographical features: TUNDRA and STEPPE. TUNDRA is a type of biome characterized by low temperatures, permafrost, and sparse vegetation, while STEPPE is a type of biome characterized by dry grasslands and shrublands. Together, these two features make up the Siberian Expanse, an area of land that covers much of northern Asia.