At or near the close of the elevation, many violent eruptions occurred on the south-west of Epomeo, during which was formed the south-west corner of the island, including Monte Imperatore and Capo Sant' Angelo (_h_, _i_). In the second or terrestrial period, when the island had practically attained its present altitude, the eruptive activity was almost confined to the eastern and northern flanks of Epomeo. At the beginning Monte Lo Toppo (_j_) was formed by a lateral eruption. In the north-west corner of the island, Monte Marecocco and Monte Zale (_k_ and _l_) owe their origin to a gigantic flow of sanidinic trachite, issuing probably from the depression which now exists between them. Lastly, towards the north-east, are the recent lateral craters of Rotaro, Montagnone, Bagno, and Cremate (_m_, _n_, _p_, _s_), the first two being the most regular and best preserved in the island. [Illustration: FIG. 14.--Geological sketch-map of Ischia. (_Mercalli._)[21]] The earliest eruption of the historic, or rather human, period appears to have taken place from Montagnone, and probably also at about the same time from the secondary crater of Porto d'Ischia (_u_), about the beginning of the eleventh century B.C. The eruptions of Marecocco and Zale are referred to about B.C. 470; and those of Rotaro and Tabor (_q_) to between the years 400 and 352 B.C. Another eruption is said to have occurred in B.C. 89, but the site of it is unknown; and three others are recorded on doubtful authority about the years A.D. 79-81, 138-161, and 284-305. The last outburst of all took place after the series of earthquakes in 1302 from a new crater, that of Cremate (_s_), which opened on the north-east flank of Epomeo, and from which a stream of lava, called the Arso (_t_), flowed down rapidly and, after a course of two miles, reached the sea. After the first eruptions to which it owed its origin, the central crater of Epomeo apparently remained inactive. All the later eruptions occurred either on the external flanks of the mountain or on radial fractures of the cone.[22] Trippiti, Lo Toppo, Montagnone and the Lago del Bagno (_b_, _j_, _n_, _p_) lie in one line, Vetta and Cremate (_c_, _s_) on another, and Garofoli and Vatoliere (_d_, _e_) on a third, all passing through a point near the town of Fontana, which occupies the centre of the old crater of Epomeo. Professor Mercalli points out that the lateral eruptions of Epomeo differ in one respect from those of Etna and Vesuvius. In these volcanoes the lava ascends to a considerable height in the central chimney, and by its own weight rends open the flanks of the cone. In Epomeo, it appears to traverse lateral passages at some depth, perhaps far below the level of the sea, and to rend the mountain by means of the elastic force of the aqueous vapour, etc., which it contains. It will be seen how important is the bearing of this difference on the occurrence of the Ischian earthquakes.