THE ERUPTION OF MOUNT KATMAl 



165 



find the volumes of ejected materials are 

 not far from equal, but the explosive 

 violence of the Krakatoa eruption was 

 by far the greater. The explosions of 

 Krakatoa were heard at a distance of 

 3.000 miles ; those of Katmai were not 

 recorded farther away than Juneau, a 

 distance of 750 miles. But it should be 

 noted that the country east of Juneau is 

 chiefly an uninhabited wilderness, from 

 which sounds are not likely to be re- 

 ported, and that the more distant reports 

 of sounds from Krakatoa came from 

 islands and sailing vessels, both of which 

 were more numerous in the Indian than 

 in the North Pacific Ocean. 



Darkness was recorded at a distance of 

 276 miles from Krakatoa and only at 150 

 miles from Katmai. The darkness lasted, 

 however, only 22 hours at a distance of 

 133 miles and for 57 hours at a distance 

 of 49 miles from Krakatoa, while there 

 was darkness for practically 60 hours at 

 a distance of 100 miles from Katmai. 



The ash from Krakatoa fell to a depth 

 of 18 inches in 24 hours at a distance of 

 66 miles, while the depth of the ash from 

 Katmai was about 12 inches at a distance 

 of 100 miles. (See also article by C. G. 

 Abbot, page 191, in this number.) 



The dust from Krakatoa fell at least 

 1.800, and possibly 3.300, miles away; 

 that from Katmai has not been recorded 

 authentically farther than Ketchikan, 900 

 miles away, but probably fell in small 

 amounts at a distance of 1.200 or 1,500 

 miles. Here again it must be noted that 

 the direction of heaviest ash fall from 

 Katmai extended into the wilderness of 

 British Columbia, where its maxinuim 

 extent is difficult to recognize. 



It is probably fair to conclude that the 

 eruptions of Krakatoa and Katmai were 

 of approximately equal magnitude, the 

 former exceeding in the brief intensity 

 of its culminating explosion, the latter in 

 sustained violence, and the two being 

 about equal in the quantity of material 

 ejected (see also pages 166, 167). 



THE GREATEST KNOWN ERUPTION 



The eruption of Tomboro, on the 

 island of Sumbawa, east of Java, in 

 181 5, if the published reports are to be 



credited, appears to have exceeded all 

 other known eruptions. It caused dark- 

 ness lasting for three consecutive days 

 at a distance of over 300 miles. Ash fell 

 to a depth of 2 feet more than 850 miles 

 away. Dust fell over an area of 1,000.- 

 000 square miles. The explosions were 

 heard at a distance of i.ooo miles. The 

 material ejected has been variously esti- 

 mated at 28.6. and even at 50 cubic 

 miles. 



The eruption of Skaptar-Jokull, in 

 Iceland, in 1783, appears to share with 

 Tomboro the preeminence as the greatest 

 eruption known. Comparison with the 

 other eruptions here described is made 

 difficult by the fact that the larger part 

 of the material ejected was lava and not 

 ash. The immense flows of lava from 

 Skaptar-Jokull exceed in volume any- 

 thing known during historic times. In 

 addition to this, there were showers of 

 ashes throughout the island, the atmos- 

 phere over Iceland was loaded with fine 

 dust for months, crops were destroyed in 

 Scotland. 600 miles away, and plants 

 were blighted and sulphurous fumes 

 were noted even in Holland, 1,100 or 

 1.200 miles away. 



The eruption of Papandayang. in 

 western Java, in 1772, was accompanied 

 by the extrusion of much larger quanti- 

 ties of material than were thrown out by 

 Krakatoa in 1883. Towns were buried 

 under ejected materials at long distances 

 from the mountain. The volcano was 

 reduced in height from 9,000 feet to 

 5,000 feet. 



The more famous eruptions of history, 

 such as those of the Mediterranean, 

 which are not mentioned above, occupy 

 a i:)rominent place in human, rather than 

 in geologic, history. These volcanoes 

 are famous because they are situated in 

 thickly settled districts, and have conse- 

 quently been familiar objects to millions 

 of people, while their eru])tions have 

 caused great loss of life and property, 

 not primarily because of their violence, 

 but because of the proximity of the peo- 

 ple and cities. 



DESCRIPTION OF THE EJECTED M.\TERI.\L 



The character of the material ejected 

 from Mount Katmai is as yet known 



