The largest wind ripples on earth: REPLY

Abstract

We thank de Silva (2010) for the opportunity to discuss the origin of the unique megaripples(MR) found on the Puna Plateau. Forman and Kröhling were invited as co-authors of this Reply,because we produced new data supplied here. De Silva suggests that the genetic relationship inferred by Milana (2009) between MR and bedrock topography is in error. The next four topics may encompass de Silva´s concerns. 1) Age of MR. 2) Structure. 3) De Silva also questioned the creep of 2–3-cm-sized volcanic clasts. 4) While creep action is not in debate, its linkage to MR final shape should be. The lack of correspondence between grain size and MR size does not accomplish the modified ballistic hypothesis. On the other hand, shape and size of MR seem controlled by topography as shown by Milana (2009, his figure 3), suggesting that wind flow structure controls, to some extent, large MR formation. However, this is hypothetical and will remain so until instrumental data can be acquired. In conclusion, we do not find any disagreement with data supplied by de Silva and the genetic relation between MR and bedrock topography. Thus, the most likely explanation for this type of bedrock erosion is the still unknown interplay between wind fl ow structure and a granular bed.