RELATION OF WIND TO TOPOGRAPHY OF COASTAL 



DRIFT SANDS 



PEHR OLSSON-SEFFER 



Mexico City 



The work on which this paper is based covers a number of years 

 and a variety of marine sea-coasts. Sand formations have been 

 studied by the writer on different coasts in Europe, on sea-shores in 

 AustraHa, South Sea Islands, North and Central America. In a 

 recent paper^ the origin and development of such sand formations 

 have been discussed and it is the intention to present here some 

 observations on the wind in its relation to the topographical features 

 of these sands. 



As a geological agent the wind exercises a considerable modifying 

 power, although its character is very unsteady. It manifests its 

 influence by carrying fine particles of soil, depositing these, denuding 

 rocks that stand in its way, and indirectly affecting the topography 

 of the earth's surface by distributing moisture and limiting vegetation. 



The moving sands of sea-shores afford ample opportunity for study 

 of the methods of the wind in its work of denudation. It can often 

 be seen how the sand carried over the surface of rocks sometimes 

 wears them quite smooth, or covers them with scratches and furrow 

 marks. This abrasion by the wind-transported material is always 

 noticeable in dune districts, at least on the wind-worn pebbles, but 

 also on the remains of trees which have been partly buried by the drift- 

 ing sand, and then the protruding parts have been slowly carved and 

 worn by the sand (Fig. 2). 



In its weathering action wind has a constant tendency to break 

 down the stones, gravel, and coarser soil particles into fine dust, and 

 it is assisted in this work by the moisture. If it was not for the loose- 

 ness of the sand, which allows the rain to percolate rapidly and thus 

 to carry the fine dust deep into the ground, the persistent combined 

 action of wind and moisture would suffice to prepare the quantity of 



^ Pehr Olsson-Seffer, "Genesis and Development of Sand Formations on Marine 

 Coasts," Boletin de la Sociedad de Geogrdfia y Estadistica, Mexico (in press). 



549 



