what I want to know is, what the devil does "lying in the direction of the prevailing wind" mean? I loathe this sort of specious precision, which gives you everything but the information you need. Given prevailing northerly winds, does the ridge run east-west, or north-south? Which side drops off sharply? and irregular, compared to what? The OED -- dearly tho I love it -- is especially prone to this irritating combination of loquacity and coyness.

An excellent point. The Infoplease definition is "a keel-shaped crest or ridge of rock, formed by the action of the wind, usually parallel to the prevailing wind direction"—infinitely superior both for the expressive "keel-shaped" and the vital "parallel." One does get the image of OED editors as ancient dodderers absent-mindedly dislodging bits of old dinners from their beards with their quill pens as they search their minds for Latinate words that will form a pleasingly Ciceronian whole; the idea of telling people in plain language what the damn thing looks like seems to be far from their consciousness.

i first encountered this word, believe it
or not, in a Time/Life book called "Planets"
published sometime in the sixties. it presented
the "new" Venus (post-greenhouse effect), &
postulated red-hot yardangs under an eternally
overcast sky. (i don't think they predicted
the fish-eye distortion from the thickness
of the air, though i think maybe Asimov, writing
at about the same time, did.) --i look forward
to finding photos of yardangs via Google Images.
i don't think our space probes are going to find any.

Well, the OED guys may have been insane, but we have no reason to believe that their beards were unkempt, do we?

The n/ng difference is hard to pick up aurally sometimes. Someone might just have been writing one language down using the alphabetic conventions or phonemics of a different one. In Taiwan I frequently heard people saying -n when they were supposed to be saying -ng, and it included speakers of standard mandarin. It drove me nuts. Perhaps the opposite occured with yardan.

Oh, sure, it's just that I would have assumed Hedin picked up enough of whatever the local dialect was to know the ablative ending. But maybe not. After all, it's kind of odd to use a form meaning 'from the cliff' as a noun meaning 'ridge of sand/rock'; maybe it was one of those "point at something and misunderstand the guide's answer" situations.

I can't answer your question languagehat, but as a someone who is trying to teach himself Turkish, I wanted to thank you for adding "yar" and "-den/dan uçmak" to my vocabulary.

-in vs -ing seein is believing: My ears are not always connected to my reading, take close and close, I'm always at a loss. A close call or close the door from one who is ill informed.

Score another one for a technically trained person working outside their field (mmm, employment). "lying in the direction of ..." means exactly what it sounds like, at least to someone in the physical sciences: the two items under discussion generally point in the same direction. However, for a general audience perhaps a better phrasing is something along the lines of "a feature of the land that points parallel to the direction the prevailing winds tend to blow in, which is created by the wind scouring away the softer materials next to it".

I first saw this word when reading a description of the origin of the spinx at Giza.

Correction-Sphinx.

Yardangs in Gordii Dorsum Region.

I first heard of yardangs from my geography teacher in the late 60's. He also mentioned "zuygons", (another geographical feature found in desert areas). I can't find any reference to this word anywhere. Perhaps it's misspelt; perhaps he took too much acid...perhaps. Any ideas..anybody...hello..