XI. A, 6 Goldsberry: Eruption of Bulusan Volcano 255 



The sulphur is probably derived from pyrite (FeS,) contained 

 in the igneous rock. In the loose material on the slopes which 

 has been recently carried down by water and by landslides, there 

 is much basalt, which is conspicuous on account of the shining 

 crystals of pyrite which are disseminated throughout the mass. 

 When pyrite is heated with a free access of air, it evolves 

 sulphur dioxide and gives a residue of iron oxide (FeaOg) 

 with 2 to 3 per cent sulphur, but when heated in an incomplete 

 supply of air or in a closed retort, it volatilizes, and upon 

 passing into a condenser or coming in contact with a cool surface, 

 the vapor condenses as flowers of sulphur. 



When pyrite burns, a considerable amount of heat is generated 

 which in ores containing over 35 per cent of sulphur is sufficient 

 in the burning of pyrites in the manufacture of sulphuric acid 

 (H2SO4) to maintain combustion after it is given an initial 

 start. It is w^ll known that the oxidation of pyrite in coal 

 seams has generated sufficient heat to fire them. In the Panama 

 Canal Zone, during the construction of the canal, carbonaceous 

 shales containing pyrite were heated to the point of combustion 

 by oxidation of pyrite, and smoke issuing from vents caused 

 much alarm to the workmen. The heat generated by pyrite 

 oxidation is a very plausible explanation for the local heated 

 conditions of the rocks as exhibited by numerous hot springs 

 and minor volcanic eruptions. 



A rivulet of water, formed by condensation of water vapor, 

 trickled from beneath a large rock resting on the rim of the 

 crater, but disappeared in the loose sand and gravel within a few 

 meters. 



On the west rim of the crater, toward the upper end, there 

 is an indentation in the rim about 5 meters long, which resembles 

 a lip and has resulted by the recent pouring out of water. It 

 is through this so-called spillway that the small stream of milky 

 water, discernible from Irosin during the eruption, flowed from 

 the crater. 



The crater wall is made up of loose, heterogeneous material 

 comprising volcanic ash, yellow sand, gravel, and bowlders. One 

 large bowlder (3 meters in diameter) is balanced on the west 

 edge of the crater awaiting future rains to wash out its infirm 

 foundation, when it will crash down the mountain side, causing 

 much anxiety in Irosin. 



CAUSES OF THE ERUPTION 



It seems very improbable that the eruption of Bulusan was 

 the after effect of some great earth movement, because the one 



