Terrain glitch

A terrain glitch is a bug made by terrain generator when generating this part of celestial body's surface. It may create freakish terrains, sometimes affect the gameplay.

Polar Glitch

This is the most usual type of terrain glitch. It occurs as a very strange terrain on the poles of celestial bodies, like Moho or Eve. It's most likely a mistake happening when terrain generator attaches height values to a sphere.

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  A probe wedged in the 5km-deep "well" at north pole of Moho.

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  Terrain at Eve's south pole

Terrain Breakage

As is shown in its name, this is a glitch that terrain cracks. It provides an "entrance" to the "inner" of a celestial body, but unfortunately, when flying something(like a poor Kerbal) into the crack, it will be destroyed immediately as it's under the surface.

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  A glitch near 23.39N, 187.80W on Minmus.