OCR Text |
Show CONCERNING VOLCANOES. The volcanoes of the Mediterranean and of the eastern and western coasts of Africa are all situated on a line, and all the volcanoes of the world have this remarkable linear arrangement. arrange-ment. It is as though they were situated sit-uated on lines of weakness in the earth's crust, where great fissures had allowed of the escape of the pent-up forces from within. Another remarkable feature in connection con-nection with volcanoes is their proximity prox-imity to the great ocean basins. All the Continental volcanoes lie along the coast line, and the islandic ones are of course situated in the midst of water. This relation of volcanoes to the seti is very suggestive when we remember that the explosive violence of a volcanic eruption is due to the escape of highly-heated steam; in fact, in a sense, a volcanic eruption is like a steamboiler bursting. The popular conception that a vol cano is a burning hill is erroneous, for fire does not occur during an -eruptive discharge, neither is there . any smoke. What has been mistaken I for flame is the glow of the molten lava, and the dust mingled with steam ! at a distance looks like smoke. A ! volcano need not be a hill at all; it is essentially a fissure through which super-heated steam, fragments of rock, and lava are discharged with explosive violence. |