CROSS SECTION OF ONE OF THE ABOVE SNOW DUNES. 



WN.v^. plateau Wmd 



THE DRYGALSKI GLACIER 51 



wind started, at the end of November, between 8.30 p.m. and midnight, and blew 

 at the rate of about 12 to 15 miles an hour until sometimes as late as about 

 9.30 A.M. the following morning, though usually it dropped earlier. Evidently in 

 winter this plateau wind blows with intense violence, ripping out the old hard snow 

 into dee^j chasms. 



The effect of the twofold directions of these strong winds added to the undu- 

 lations caused by the 

 pressure which impels 

 the ice forwards, and 

 probably the etching 

 effect of the sun on the 

 ice and snow, combine to 

 make the surface of the 

 Drygalski Barrier in 

 summer very difficult for 

 sledging. As we ad- 

 vanced, the undulating 

 old sea ice raised rounded 

 ridges to bar our pro- 

 gress. The crests of the 

 waves rose first to heights 

 of 8 to 10 feet above 

 their troughs ; then to 

 20 feet; gradually, with- 

 out any visible trace of 

 a tidal crack, the sea ice 



rose to the blue or pale 



green ice of the glacier. 



The glacier surface here Yia 9 



resembled thatof astorm- 



tossed sea suddenly frozen. Long embankments of hard snow trending about 



E. 30° S. and W. 30° N., parallel to the plateau wind, joined billow to billow. The 



north-easterly faces of these embankments were precipitous and often overhung 



with a snow cornice, producing a seemingly endless series of more or less impassable 



ravines. On following the embankment for a few hundred yards it would be found 



that the bottom of the chasm shallowed, and it was found possible to lower the 



sledge and get across it. 



The structure is illustrated diagrammatically in Fig. 9. 



The extraordinary structure produced in the surface of this glacier as a result 

 of a combination of pressure ridges, blizzard sastrugi, and plateau wind sastrugi, is 

 shown on Plate XI. It presented a perfect labyrinth of high broken ridges, with 



S.orSxE. Blizzard 



» y 



Glacier Ice With recent crevasses (black), and 

 old crevasses nonfilled with sapphire-blue ice (white). 

 Snow lids of recent crevasses (dottedj 



