6o PRINCIPLES OF STRATIGRAPHY 



northern Great Britain, and in Holland. Dust from Tomboro fell 

 on Sumatra, a thousand miles away. Krakatoa ashes fell inches 

 deep at distances of nearly i,ooo miles from the volcano, and small 

 quanrities fell even in Holland. Dust from Colima in Mexico fell, 

 in February and March, 1903, at points over 200 miles north and 

 east of the volcano, and the ash from Santa Maria in Guatemala in 

 October, 1902, covered all the northern part of that country and 

 most of the states of Tabasco, Veracruz, and Oaxaca in southern 

 Mexico. At Tapachula, 40 miles away, the ashes were 19.5 centi- 

 meters thick. 



"Ash from Coseguina in Nicaragua in 1835 covered an area of 

 1,500,000 square miles and even reached Jamaica, more than 750 

 miles away. The dust from the eruption of Cotopaxi in Equador 

 in 1877 fell at Guayaquil, 150 miles away, to the amount of 315 

 kilograms on every square kilometer during the first thirty hours 

 of the fall. Once 209 kilograms fell in twelve hours. The dust 

 ejected by this same volcano in 1888 amounted to more than 2,000,- 

 000 tons. On this occasion the dust cloud traveled 85 miles in six 

 hours. At the eruption of Tarawera in New Zealand in 1886, 

 1,960,000,000 cubic yards of dust were discharged in five or six hours 

 and covered a land area of over 6,000 square miles. Much more 

 dust fell into the sea. Dust from the eruptions of La Soufriere and 

 Pelee in 1902 fell plentifully all over the West Indies and especially 

 at Barbados, 130 miles from Pelee and 225 from La Soufriere. 

 Dust from the eruption of Pelee in 1812 is said to have reached the 

 Azores. Dust from X^esuvius has been observed in Greece, in 

 France, and in Austria." 



Volume of Dust Falls. In 1863 a rain of dust occurred on the 

 Canary Islands, the volume of which was estimated at 3,944,000 

 cubic meters. (Fritsch-34 : ^/.?.) Free (33:98) reduces this to 

 5,900,000,000 kgm. or 6,500,000 tons. The dust fall in Eng- 

 land on February 22, 1903, is said to have furnished 9,100,000,000 

 kilograms or 10,000,000 tons of material, but the data are not wholly 

 reliable. The great dust storm of March 9-12, 1901, however, 

 brought to Europe 1,782,200,000 kilograms or 1,960,420 tons of dust, 

 while North Africa received 1,500,000,000 kilograms or 1,650,000 

 tons. This dust deposit thus covered at least 300,000 square miles 

 of land surface, and 170,000 square miles of ocean, and, accord- 

 ing to Walther, traveled in part at least a distance of 4,000 kilo- 

 meters or 2,500 miles. Altogether 3,282,200,000 kilograms or 

 3,610,420 tons of dust fell. For the European area (437,500 square 

 kilometers or 168,437 square miles), the fall averaged a layer of 

 dust 0.239 mm. thick. Assuming the usual dust falls together with 



