412 E. O. HOVEY STRIATIONS AND U-SHAPED VALLEYS 



of 90 degrees to skirt a ridge called Morne Lenard, 6 Between Morne 

 Lenard and the main mass of the mountain there is a comparatively low 

 col over which rushed part of each cloud that was divided into two parts 

 on striking the narrow front presented by the morne. The surface of the 

 ground here was completely denuded of soil and the tuff-agglomerate was 

 scored with hundreds of parallel straight grooves many (10 to 15) meters 

 long and several (2 to 10 or more) centimeters deep. Such grooves in 

 the side of Morne Lenard are shown in figure 2, plate 38, made from a 

 photograph taken in May, 1908. Figure 1, plate 39, is a near view of 

 a part of the same surface, taken in February, 1903. The latter view 

 shows, too, the manner in which the comparatively hard component frag- 

 ments of the agglomerate were planed off without being dislodged from 

 the softer matrix. Such fragments when removed from their present 

 surroundings, either naturally or artificially, would make good imitation 

 "glacial bowlders ;" or the whole surface, if buried beneath an accumula- 

 tion of volcanic debris, would have close resemblance in appearance to a 

 glaciated surface under a covering of till. The photograph given in fig- 

 ure 2, plate 38, furthermore brings out well the rounded, glaciated ap- 

 pearance of the morne as viewed from the east and north, the lower part 

 closely resembling a true glacial roche moutonnee. 



Other bluffs showing the sand-blast action typically were observed 

 along the right bank of the Eiviere Claire, on the right bank of the 

 Blanche opposite Morne Lenard, on both walls of the Biviere Seche gorge 

 (see figure 2, 7 plate 39), and elsewhere — in fact, wherever in the zone of 

 annihilation a surface was opposed to the advance of the eruption clouds. 

 The direction taken by the striae depended on the position of the striated 

 surface with relation to radii drawn with the crater as a center. 



AVALANCHE ACTION ON MOUNT PELS 



The Morne Saint Martin is a rather flat ridge sloping away from the 

 crater and not fully exposed to the fury of the volcanic sand-blast. Here 

 corrasion was observed, with grooves and striae running at an angle to the 

 radii of the zone of annihilation which were not to be accounted for by 

 reference to the eruption clouds for their origin. This flat ridge is mid- 

 way of the mountain and has a slope of 10 to 15 degrees, the slope below 

 being from 3 to 5 degrees, and the slope of the outside of the old cone 

 above being about 20 to 28 degrees. During intervals of mild activity 



6 Erroneously called Morne Saint Martin in my earlier papers. The real Morne Sainl 

 Martin is a less prominent ridge south and east of Morne Lenard. 



7 This is a near view of part of the scored bluff illustrated in Bull. American Museum 

 of Natural History, vol. xvi, pi. 40, fig. 2. 



