Ravine

Ravines are generated structures that may be added in Update 0.14.0. They are large cracks in a Minecraft world that are less than seven blocks wide but can be 20 to 30 blocks deep, often leading to various underground structures and rare ores.

Uses
Ravines by themselves have no use, but they often reveal many underground structures like Caves, Abandoned Mineshafts, Strongholds, and Dungeons. They often also reveal rare ores like Diamond and Emerald.

Trivia

 * Ravines were originally rumored for Update 0.9.0, and then 0.10.0.
 * However, they were not added.