Volcanic Disturbances in West Indies 265 



1 . That Montagne Pelee is one of the 

 chain of ancient volcanic mountains, 

 dating from Tertiary time, rising to a 

 height of 10,000 feet above the ocean 

 bottom along the interior side of the 

 semicircular ridge across the entrance 

 of the Caribbean Sea. 



2. That the volcanoes of this ridge 

 have been successively forming on its 

 western side. 



3. That the material, like that of the 

 Cretaceous volcanoes of the Great An- 

 tilles, is entirely andesitic. 



4. That the eruptions, especially of 

 the later periods, have all been of the 

 explosive type, unaccompanied by lava 

 flows. 



5. That the historic eruptions have 

 taken place between long intervals of 

 solfataric quiescence. 



The geology of Martinique, as out- 

 lined, shows that Pelee is an old vol- 

 cano, and that the present eruptions, 

 instead of being sudden and a new phe- 

 nomena, are but the maximum of a 

 series of solfataric conditions which 

 have continued through a long interval, 

 of geologic time. The eruption of 1851 

 produced similar phenomena of ash, 

 mud, and steam ejected from the same 

 vents, and affected a similar area. The 

 geological structure of the mountain of 

 Pelee shows, in its layers of mud, pum- 

 ice, and tuffs, that these processes have 

 been going on at long intervals from 

 time immemorial. The first important 

 deduction, then, is that the present 

 eruption of Pelee is the repetition of 

 events which have taken place time and 

 time again at the same locality, and that 

 the mechanism of the volcano is all old 

 and prehistoric — the same central crater 

 and lateral vents. So far as recorded, 

 the volcanic mechanism of Pelee is the 

 same as it was at the date of its discov- 

 ery in 1894. No new craters have 

 been formed, but merely old craters 

 reopened. The principal feature of this 

 mechanism is the crater of Montagne 

 Pelee — simply a conical chimney lead- 



ing from the hot magma of the earth 

 and built up of its own ejecta. This 

 chimney is a vertical tube extending 

 downward to the interior magma, which 

 ascends as a great column of molten 

 matter. The bowl or crater of Pelee 

 summit is the top of the chimney. 



FEEBLENESS OF THE PHENOMENA 



The fact that there were no serious 

 earthquakes shows that the explosions 

 within the crater were not exception- 

 ally severe ; in fact, not as severe as 

 many which have taken place within 

 the Antillean vents, with deadly earth- 

 quake effects, without causing erup- 

 tions. No evidence has yet been de- 

 duced showing that the present erup- 

 tion was preceded by or has resulted in 

 any serious openings or fissures in the 

 sea bottom, which could have caused it 

 by the sudden letting in of the waters; 

 neither is there, in the structure and 

 geographical position of the oceanic 

 Caribbee Islands, any condition which 

 enables us to hypothesize a deposit from 

 sedimentation which would produce 

 weight resulting in the creation of such 

 fissures. 



The conical configuration of the moun- 

 tain ; the repetition in geological time 

 of the eruptions at the same locus ; the 

 absence in the structure of the island of 

 conspicuous volcanic dikes and sills ; 

 the failure of other and more conspic- 

 uous solfataric vents along the Caribbee 

 chain to erupt, indicate that the shape of 

 the ascending magma is cylindrical ra- 

 ther than elongated, as would have been 

 the case had it arisen along the fissure. 



The eruption of 1902, which is still 

 in progress, has been one of progressive 

 intensity for an unknown period of time. 

 The waters of the L/Etang de Palmiste 

 in the top of the crater bowl have been 

 warm for several years, and as far back 

 as May, 1901, sulphurous fumes and 

 vapor were noticed escaping. Conspic- 

 uous activity suggestive of intense erup- 



