Was this a sudden shift of several feet on the ground level (because the underlying ground was in tension for years)? Or how does a crack that big form? Is it e

Was this a sudden shift of several feet on the ground level (because the underlying ground was in tension for years)? Or how does a crack that big form? Is it even as big as the hole? I.e. if we were to measure from two points across the crack - did they move as much as the crack is wide? Who would own the new land?