I need to subset mosaics of remotely sourced data to the extents of several prominent North American mountain ranges, starting with the Sierra Nevada. After searching for the boundaries of the range it has become clear to me that this isn't quite as straightforward as I thought: wikipedia, peakbagger, the California DFG, the Sierra Nevada Conservancy and my desktop copy of google earth all show clearly different boundaries for the range. Clearly, the border a mountain range is less black and white than, say, an administrative boundary.
Are there "official" (by which I mean either authoratative or generally agreed-upon) definitions of the extents of North American mountain ranges, and if so, where can they be found?
Obviously it would be nice if it existed as a shapefile, but I can digitize it myself if it's just a list of bounding points.
To clarify, I don't particularly care if the boundaries are somewhat arbitrary/inaccurate from a strict geological perspective, as long as they come from an authoritative/trusted source. I'm not studying geological processes- I just need a reasonable citation.