THE NATIONAL GEOGRAPHIC MAGAZINE 



14" 



weighing upward of a hundred pounds 

 are frequent, and everywhere the ejecta 

 are much coarser than the ash from Kat- 

 mai, indicating that the explosions were 

 less violent. 



After the first violent outburst the ac- 

 tivity apparently gradually diminished in 

 intensity until most of the ejected ma- 

 terial was thrown only a short distance, 

 forming in its fall a circular crater ring 

 immediately surrounding the vent. This 

 being seven-tenths of a mile in diameter, 

 is one of the largest explosion craters in 

 the world, very much larger than Pelee 

 or Vesuvius, and would be a feature of 

 primary interest in the region were it not 

 dwarfed by the vast crater of Katmai. 



THE GREAT LAVA PLUG OF NOVARUPTA 



As the explosive period drew to a close 

 the lava became more and more pasty, 

 until among the last stones thrown out 

 were numerous masses of lava stiff 

 enough to retain their shape, yet so hot 

 that their surface is cracked open from 

 the contraction incident to cooling, giving 

 the characteristic "bread crust" appear- 

 ance. These are the only lava "bombs" 

 found in the Katmai district. Nowhere 

 are there any typical bombs formed by 

 masses of lava thrown out while still 

 liquid and assuming a rigid spheroidal 

 form while still in the air. Indeed, no- 

 where else were even "bread crust" 

 bombs found. 



After explosive activity had ceased 

 there was a slow extrusion of pasty lava 

 from the vent. This has been pushed 

 up until an immense plug of lava has been 

 formed 1,200 feet in diameter and 250 

 feet above the floor of the crater. The 

 surface is covered with an indescribable 

 confusion of fragments of all sizes, 

 shapes, and colors, formed by the frag- 

 mentation of the lava from the strains 

 set up by unequal contraction while cool- 

 ing. 



We could only guess the distance 

 through this mantle of fragments to the 

 still molten lava beneath. The fact 

 should be noted that nowhere in the 

 whole district did we see any evidence of 

 a lava flow in connection with the pres- 

 ent eruption. This mass of rock, which 

 from the beginning was evidently very 



Photograph by Robert F. Griggs 

 A CHUNK 01? PUMICE THROWN OUT BY 

 NOVARUPTA 



So violent was the explosion of Novarupta 

 that quantities of its pumice are scattered over 

 an area ten miles in diameter. In these de- 

 posits, cinders weighing upward of a hundred 

 pounds are frequent (see page 144). 



pasty, is the nearest approach to molten 

 lava to be found in this region. 



That somewhere beneath the surface 

 of this plug the lava is still molten is 

 abundantly evidenced by the tremendous 

 quantities of smoke continuously given 

 off. Often this cloud fills the sky for 

 miles, even drifting through Katmai Pass 

 and obscuring considerable areas on the 

 other side of the range. At other times 

 the smoke forms an erect column as much 

 as two miles high (see page 140). 



Around Novarupta the earth is all shot 

 to pieces with more and larger steaming 

 fissures than are to be found elsewhere, 

 so that only with difficulty one finds a 

 path through the bewildering maze of 

 vents. The climb over the rim of Nova- 



