DESCRIPTION OF THE ISLANDS: SAUNDERS I. 173 



In all places where the rock is exposed the underlying strata consist of black basalt. 

 This composes the plateau at the northern end, and here it has the typical columnar 

 structure seen at Candlemas and Zavodovski, with cliffs 30 to 40 ft. high, eroded by 

 wave action and carved into small bays and gullies. To the west of Harper Point two 

 large masses, apparently composed of fine volcanic ash or mud, lie on the surface of the 

 plateau. Mt Michael, as will be seen from Plate XX, fig. i, is most evidently volcanic, 

 a feature first noticed by Capt. Hansen in 1927. During the whole time that the summit 

 was clear it emitted great puffs of steam and vapour at intervals of a few seconds. The 

 cone, none the less, is deeply covered with glacier, extending to the sea on both east and 

 west sides. The surface of the ice is for the most part smooth, with only an occasional 

 ledge of rock projecting through it; but on the northern side a deep rift or gulley, 

 partially free from snow, extends up the mountain, calling to mind the curious fissures 

 seen in the cone of Zavodovski. The lower slopes of the glacier are much blackened 

 by wind-borne dust and debris. 



The south-eastern extremity of the island consists of a range of hills with heights of 

 700 and 800 ft., on which the snow cannot lie owing to the warmth of the ground 

 (Plate XXI, fig. 3). Everywhere, except at Nattriss Point, these hills are composed of a 

 fine-textured grey material, which we believe must be either fine ash or volcanic mud. 

 It is very easily eroded and on both north and south sides is scored by streams of water 

 from the melting snow into parallel runnels and ravines — some of them at least 10 ft. 

 deep. Snow fell while we were at the island : it melted rapidly in most places, but lodged 

 for a longer time in the ravines, giving the hills the appearance of being covered with a 

 finely woven white shawl. 



Where the hills join the main body of the island, there is a huge yawning crater, 

 formed of this same ash or mud (Plate XXI, fig. 2), and, since no steam or vapour could 

 be seen issuing from it, we assume that it is extinct. On the southern side of the pro- 

 montory a large portion of the cliff has fallen away, exposing to view a remarkably perfect 

 half-section of a crater (Plate XX, figs. 2, 3). As the island is approached from the 

 south this bisected crater is a most conspicuous feature, and on close inspection it can be 

 seen that the strata in the cliff face on either side of it run parallel to the edges of the 

 depression and to the top of the cliffs, just as in a text-book section of a typical volcano. 

 The surface of the depression is scored with radial grooves similar to those on other parts 

 of the hills and the diameter of the crater is not far short of half a mile. At Nattriss Point 

 (Plate XXI, fig. 4) and at a number of other places a layer of black basaltic lava can 

 be seen at the water line. The cliff section, however, shows clearly that the hills are com- 

 posed throughout of ash or mud, and that their appearance is not due to a mud-flow 

 covering other materials. At one or two points on the western side of the island ex- 

 posures of red tuff were seen above the basalt. In the south of the island, to the west of 

 the bisected crater, a small mound of mud or ash protrudes through the glacier and is 

 evidently still warm. Water from the snow melting on its surface has carried runlets of 

 mud over the surface of the glacier towards the sea (Plate XXI, fig. 5). 



The formation of the hills in the south-east corner of Saunders has no counterpart in 



