86 P. Waltz — Popocatepetl Again in Activity. 



measurements of Aguilera and Ordonez, 600 m. (nearly 

 E-W), while the smaller axis has a length of 400 m., 

 a depth from the highest point of 500 m., and from the 

 lowest portion of the rim 250 m. During the pauses 

 between the rather infrequent steam explosions one hears 

 only the whistling of the fumaroles and the solfataras, 

 which produce a noise similar to that of a number of steam 

 engines blowing off steam at the same time. 



Two of these solfataras in particular were known to me 

 from my former ascension of the crater in 1905 ; they do 

 not originate in the bottom of the crater, but lie in the 

 lower portion of the crater walls in the southeast and 

 southwest portion, and therefore have not yet been 

 covered by the mass of bowlders of the plug, the form of 

 which probably corresponds to that of the chimney. 



It is too early to prophecy anything about the further 

 development of the activity of Popocatepetl. If the 

 observation said to have been made during the excursion 

 on the first of November should prove to be exact, and 

 the plug had been rising during the fourteen days since 

 my ascent and investigation, for about 20 to 30 m., as those 

 gentlemen state, then we may assume that the activity 

 of the volcano is increasing. This we can conclude also 

 from the development of steam, which is becoming contin- 

 uously stronger. We cannot expect to see a Pelee-needle 

 rising from the crater, with its depth of 500 m. as was 

 mentioned above, but we can expect that the crater will 

 become filled slowly with solid block-lava, produced by 

 the breaking up and dismemberment of the column of 

 solid andesite which fills the chimney. Of course not only 

 years, but tens of years or even a whole century, may 

 pass before the mass of bowlders fills the whole crater. 

 Yet before the whole crater will be filled with these masses 

 another event may take place as has been the case in the 

 volcano of Colima, where in 1869 an adventitious cone 

 with a double sunmiit was formed which produced a 

 small lava stream. For the formation of such a lateral 

 adventitious cone the east and south sides of Popocatepetl 

 are especially predestined, as they are characterized by a 

 particular thinness of the crater wall. 



Finally, there exists another possibility : The explosive 

 power of the focus, be it through endogene processes in 

 the magma or be it through the accumulation of pressure 

 due to a casual closing of the emanation channels still 

 open at the present time through the immense masses of 



