Isostasy
The state of gravitational equilibrium between Earth's lithospheric crust blocks floating at depths determined by their thickness and density upon the denser mantle.
Governing formula
Airy Model: h_root = h_mountain (ρ_crust / (ρ_mantle - ρ_crust))
SI unit
Meters (Crustal Root Depth)
In depth
Described by the Airy and Pratt models. Thick, low-density continental crust floats higher and develops deep roots in the mantle (like icebergs), while thin, dense oceanic crust sits lower, forming ocean basins.
Examples in the real world
Post-glacial isostatic rebound where northern landmasses (like Scandinavia) slowly rise as melting ice sheet loads are removed.