Memory arrays and methods used in forming a memory array comprising strings of memory cells

A memory array comprising strings of memory cells comprises laterally-spaced memory blocks individually comprising a vertical stack comprising alternating insulative tiers and conductive tiers. Operative channel-material strings of memory cells extend through the insulative tiers and the conductive tiers. Intervening material is laterally-between and longitudinally-along immediately-laterally-adjacent of the memory blocks. The intervening material comprises longitudinally-alternating first and second regions that individually have a vertically-elongated seam therein. The vertically-elongated seam in the first regions are taller than in the second regions. Additional embodiments, including method, are disclosed.