PHYSICAL HISTORY OF BOGOSLOF 327 



PHYSICAL HISTORY. 1 



The known history of other volcanoes makes it possible, 

 with moderate and legitimate use of the imagination, to 

 construct from the records here assembled the physical 

 history of this locality. Some thousands of years ago 

 a crack in the earth was opened deep down under Bering 

 Sea and lavas welled out. Some of them may have 

 flowed over the bottom as liquids until they congealed; 

 others were doubtless burst into fragments by the expan- 

 sion of imprisoned steam. This occurred, not once but 

 many times, until at last the accumulated rock made a 

 mountain high enough to show its head above the sea. 

 Then the forces of the air attacked it and storm waves 

 beat against it and it was worn and washed away, till there 

 remained above water only a pyramidal rock with a bit of 

 beach or spit that had been built up by the waves from 

 the waste of the original island. It was in this condition 

 when first seen by white men, the remnant crag being 

 Ship Rock. In 1796 there was a new eruption, breaking 

 out a little to one side of the last, so as to form a separate 

 island, Old Bogoslof; and this in turn was attacked by the 

 elements and rapidly reduced in area. Yet another erup- 

 tion, in 1883, took place on the opposite side of Ship Rock, 

 creating still a third island, New Bogoslof; all three stand- 

 ing on the submarine mound or mountain that previous 

 eruptions had built. 



Since then all changes, except a slight upheaval, have 

 been wrought by storm and sea. The islands have been 

 gnawed about the base until girt by steep cliffs. Ashes 

 and loose rocks have been washed down to the sea, leav- 

 ing the firmer masses as towers and peaks; some of these 

 have afterwards been sapped and have fallen; and the out- 

 lines have suffered almost kaleidoscopic changes from year 



1 This note on the physical history of Bogoslof was prepared at my request by 

 G. K. Gilbert. C. H. M. 



