Mantle makes up 84% of the Earth's volume and has an average thickness of approximately 1,800 miles (2,900 km). It is dense, hot, and primarily solid although in places it behaves more like a viscous fluid as the plates of the upper mantle and crust gradually "float" along its circumference.
The Earth's mantle is dense, hot, and primarily solid although in places it behaves more like a viscous __________ as the plates of the upper mantle and crust gradually "float" along its circumference.