THE 



AMERICAN JOURNALOFSCIENCE 



[FOURTH SERIES.] 



Art. XXX — The Circulatory System in the Halemaumau 

 Lava Lake during the Summer of 1911 • by Frank A. 

 Perret. 



The degree of activity at Halemaumau varies between com- 

 paratively narrow limits within which, nevertheless, we may, 

 for convenience, distinguish three principal phases, viz.: the 

 sub-normal, normal and super-normal. 



In the first case, the lava — generally very low in the pit — 

 may be entirely covered by a solid, non-luminous crust, or it 

 may be altogether absent as the result of a so-called " break- 

 down," by which inelegant epithet is meant a subterranean 

 lateral outflow of lava from the conduit, thus draining the 

 overstanding crater of its liquid contents.* 



At the other extreme, under super-normal conditions there is 

 a lake of liquid lava filling the crater basin from side to side, 

 whose temperature and mobility are of the highest order. 

 Fountains play over the entire surface and the ascending gases 

 so thoroughly stir and heat the mass of liquid that the surface 

 remains quite free from crust. 



Between these extremes — abnormal as regards their distribu- 

 tion in time — w T e find a condition which frequently prevails for 

 months, and even years, with occasional variations and which 

 may, therefore, for our day, be considered as the normal state 

 of activity. The supply of heat is such that the temperature 

 of the lava oscillates about the point of its congelation in con- 

 tact with air or rock, with a tendency to fall below it. The 

 condition might be described as a semi-liquid phase. There is 

 a lake of liquid lava the dimensions of which are restricted by 



* It will be seen that this latter condition does not indicate any general 

 lessening of the volcano's activity but only as regards the terminal crater. 



Am. Jour. Sci. — Fourth Series, Vol. XXXV, No. 208. — April, 1913. 

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