Page:Popular Science Monthly Volume 71.djvu/50

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filled with debris and poisoned with bitter sulphurous water that the fish have died. Some say that the Shirakawa, which means 'white river,' owes its name to the milky color that it has been known to assume at such times. Loss of life has been occasioned by these outbursts, but the records do not make it clear to what extent. Reference is made in records to fiery rocks sometimes of great size that have been blown out, but lava flows do not seem to have assumed importance. Explosive eruptions of fine debris, as shown by the mud cone, have been predominant during the later history of the volcano.

PSM V71 D050 Recent lava flow on the south side of naka dake.png

Fig. 8. Recent-looking lava with smooth flow structure that has flowed down a gully high up on the south side of Naka-dake. In the distance, far across the great crater of Aso, may be faintly seen the horizon line of the outer wall. The whole foreground is covered with barren volcanic rock.

The greatest eruptions of very recent times were in the winter of 1873 to 1874, when unusual activity continued during several months and ashes covered the ground to a distance of 18 miles; in the winter of 1884, when ashes were blown over Kumamoto, making it so dark there at a distance of 25 miles that lamps had to be used for three days; in 1889, during the year of the Kumamoto earthquake, which was the year following the great explosions of Bandai-san in central Japan; and lastly in 1894, when the floor of the modern crater was somewhat altered.

The problem of old Mount Aso is a deep one. One can not view its gigantic outlines without wondering what forces could have molded them, what could have been the steps in the process of formation of this huge pit, its level floor, its steep walls, the gentle slopes radiating