78 PRATT, 



Bignay Point will probably similarly be changed before the work of 

 cutting down the new shore line is finished. These peninsulas were at 

 the northeast end of the island. This part sank about 3 meters, judging 

 from submerged tree stumps. A new beach is building over an old 

 sugar-cane field on the southeast shore of the island. Cogon grass and 

 stumps of trees with their roots intact could be seen all around the island 

 beneath about 1 meter of water. 



The relative level of the lake is changed. It is lower by about 1 

 meter on its south shore line and is lower by a smaller amount on its 

 north shore. The water in the upper part of the Pancipit River stands 

 at a lower level now than formerly. The subsidence of Volcano Island 

 would tend to lower the level of the lake on its shores but apparently 

 not to such an extent as has occurred. It is not improbable that the 

 whole shore line of the lake has risen slightly, reacting from the sub- 

 sidence of the island at its center. 



CHANGES IX THE CEATEH. 



Outwai'dly, Taal Tolcano was little changed by its recent eruption. 

 The absence of vegetation and the smooth drifted surface of the ash 

 covering which is almost white in the sunlight, give the island an 

 appearance of a vast snow heap. The crater rim is unbroken and' save 

 for minor fissures and cracks is intact. Sulphur is burning rather vigor- 

 ously part way down its outside slope on the north side of the crater. 

 This had never been noted before the eruption. 



The interior of the crater has been transformed. Plate III, showing 

 maps of the crater before and since the recent activity, and Plate IV, 

 showing cross sections made from these maps, indicate what change has 

 occurred. The well-known Green Lake and Yellow Lake, which were 

 small bodies of water, one of which (Yellow Lake) was quite shallow, 

 referred to in descriptions of Taal since earliest historic times, are 

 gone. In the position of the former Green Lake there is a new one, the 

 water of which appears milky-white, due to suspended solid matter. 

 The level of this lake was on February 17 approximately 70 meters 

 below that of the sea.-^ Green Lake had stood 5 meters above sea level. 



-^ The map of the changed ci'ater was made by reading vertical and horizontal 

 angles from kno\\Ti points with a Versehoyle pocket transit. The same instru- 

 ment was used for mapping the fissure system, distances being paced. In 

 mapping the crater, elevations were determined by reading vertical angles from 

 seven prominent points on the crater rim to two points on the edge of the crater 

 lake ( located from the horizontal angles ) . Readings from the rim to the lake 

 • were checked by reading the same angles from the lake rim. The elevations on the 

 rim were determined accurately by a recent Bureau of Lands survey, and were 

 changed only slightly, if at all, by this eruption. The results were averaged and 

 the figure given should not be in error more than 10 per cent. A superior aneroid 

 barometer was read at each elevation and the angle determinations were thus 

 checked. 



