Using map style coordinates as laid out below:
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The apparent crack at B1 appears to be filled with 'rind'. But when looking at the same region in the full scale jpg, I would say there is no rind filled crack, only dust covered rock. The dust appears to be coming from deflected wind off the lower (A2 area of pic) inverted V shaped rock ( McKittrick? ) that sticks out from the face of El Capitan.
If my reasoning is correct, then the apparent channel at B1 was carved by wind blowing right to left up the face of El Capitan. While this particular area (B1) appears to be wind caused, I don't think it is probable the other rind filled cracks were caused by similar means. However, It also seems a bit implausable, that an impact would so neatly space the observed bedrock fragments.
Has anyone heard Nasa's explaination of the rind filled cracks?