Some canyons are noncontiguous, 1-2 blocks wide and can form a very straight line.

I think these examples are supposed to be ravines. See attached pics.

Random seed: -6515423362168972464
World type: Default

(Coordinates are slightly rounded. Switch to creative / fly.)

Desert ravine: teleport 1370 100 -960
Savanna ravine: teleport 1580 100 680
Jungle ravine: teleport -240 100 510
Plains ravine: teleport 385 100 100