 Lunar crustal dichotomy

The hemispheric contrast involving thicker, generally higher feldspathic crust on the far side of the Moon, compared with generally thinner crust, more extensive lunar maria and the concentration of KREEP-rich material on the near side of the Moon. Crustal mass, topography, chemistry and later volcanic deposits are different observables. A proposed mechanism must explain their relationship rather than identify the contrast solely with visible dark maria.