July 30, 1915] 



SCIENCE 



151 



Fig. 1. The lava lake in the pit of the crater HaJemaumau, at the time of the maximum activ- 

 ity about January i, 1915. The main lake and the northwest pond, especially the west cones and pots, 

 were the sources of the lava flows which built up the 1914 floor. The west and southwest cones de- 

 veloped into ponds, and the southeast cone (SE.) into an aim to the main lake like the south arm 

 (S.). Between the northeast (or east) arm and the main lake is the crag which rose and sank with 

 the lake, as a counterbalance to the flooding of the floor as indicated by arrows. South of the 

 floor is a talus slope with a fragment of a ledge at the base. Around the rim of the pit are remnants 

 of the 1911-12 floor and of 1S94 cave-ins. 



During the last of February, the lava re- 

 mained at a level of about 460 feet below the 

 rim, with daily variations, and especially rises 

 at noon and midnight, of 2 to 20 feet. Foun- 

 tains were very active in the Old Faithful re- 

 gion, and the streaming was variable, and often 

 rapid. At the sides of the lake caves would 

 splash, and the lava run in as long as the gas 

 explosions continued. Some of the caves re- 

 mained active for five minutes or less, others 

 for hours. Migrating fountains were active, 

 and frequently a fountain area near the center 

 of the lake, into which lava was streaming, 

 would suddenly move to one side of the lake 

 and form a splashing cave. 



On February 23 and 24, the lake rose to 

 within a foot or two of the 1915 small floor on 



the south side. The following day the lava 

 flooded the lower floor at noon and at night, 

 with fountains spraying 50 to 80 feet high. 

 The streaming was from the northeast toward 

 the west and less actively toward the south- 

 east. Four new driblet cones appeared in the 

 western trench at the site of the pots and 

 cones from which the flows came at the close 

 of 1914. On the 2Yth, Old Faithful was play- 

 ing at intervals of 10-20 and 50-60 seconds. 

 On the 28th, a sudden rise at noon flooded the 

 lower floor. 



A small arm to the lake on the southeast 

 developed by March 1, and the following 

 morning a clockwise vortex developed in it, 

 with an inrush at a rate of 8 miles an hour 

 into the east side, the lava pouring out of the 



