Ca. 415–400 Ma ultrahigh-pressure (UHP) eclogites in the Western Gneiss Region of Norway occur in three discrete ∼2500 km² to >100 km² antiformal domains separated by high-pressure rocks. Disparate eclogite ages suggest that the northern UHP domain and the two southern UHP domains are separate crustal blocks that experienced and were exhumed from UHP conditions at different times. The UHP rocks underwent isothermal decompression to <20 km depth in ∼5 m.y., suggesting adiabatic exhumation of a >20–30 km thick UHP body. The UHP slab rose coherently from mantle to crustal depths and was exhumed through the crust progressively...