VOLCANOES

are vents in the earth’s crust from which molten rock, ashes, and steai. are ejected. The lava tends in time to heap up a conical eminence round the vert, thus forming the crater or cup. They are of three kinds: (1) extinct, (2) dormant (i.e., temporarily inactive), or (3) active. A volcano may be either explosive (as in the case of atoa) or effusive (as seen in the great cones of basaltic lava in the Sandwich Islands). Minor varieties are salses, or mud volcanoes of the Crimea, fumaroles, or steam fi ures, and the solfataras of Italy, where sulphur fumes escape through vents in the earth. The geysers of Iceland (see Grysur) denote spent volcanic activity. Notable active volcanoes are: in June 1923 with great violence. The crater was shattered and great streams of lava flowed down the mountain sides, destroying vineyards and other property. The Peck of Teneriffe, 12,000 ft., on Islands; over 3,000 ft.; active since Homer’s time; constantly sending out steam and occasionally showers of stones, which generally fall back into the crater. Mont Pelee, in island of Martin i que, was scene of violent eruption, 1902. St. Pierre, the cap., was destroyed, and 30,000 perished. The side of the volcano was torn away. Krakatoa, on Krakatoa I., Java. Mount Hecia, in Iceland, 5,000 ft., has been jn constant eruption since 9th cent. There are active volcanoes in Hawaii, in N.. Pacific Ocean, and in Réunion, Japan, and Mauritius. Antarctic volT error, 11,000 7t., extinct. See Potar ReEGIons. The geographical distribution of active volcanoes is of interest. By far the greater number stand near the sea; this is probably due to the fact that many coastlines are determined by earth folds. ring of volcanoes encircles the P.. regards the origin of volcanic activity, it is fairly certain that at depths of a few miles in the earth’s crust, y in regions which are undergoing or have recently undergone the proce of folding, great ma es of rock exist at a very high temp. and under great pre ure. They contain much water vapor, occluded, but ready to expand when the pre ure is relieved. The temp. is not le than 1,200° C., and may be considerably above this. Escape tends to take place along lines of weakne . In Britain there is evidence of repeated volcanic activity in bygone imes.