530 Professor J. W. Gregory — The Ambrym Eruptions, 



Although the existence of the suspected early rocks is unconfirmed, 

 Sir D. Mawson collected at Espiritu Santo a series of limestones 

 which Mr: Chapman (1905, p. 273) identified by their Foraminifera 

 (Lepidocyclina) as Aquitanian and Burdigalian. They are therefore 

 Lower Miocene, and would be also Upper Oligocene according to the 

 classification which refers the Aquitanian to the Oligocene. 



These Lepidocyclina limestones are shown by Mawson to rest on an 

 older volcanic series, which he attributes to the Oligocene or the 

 base of the Miocene. The limestones are burst through by a later 

 volcanic series, the earlier tuffs of which Mawson regards as possibly 

 Pliocene. These tuffs form the beginning of the volcanic period that 

 includes the modern eruptions. 



The Miocene rocks occur in south-western Espiritu Santo, and 

 their arrangement shows that they are part of a great upfold which 

 formed the New Hebrides ridge. 



The later limestones are recent coral reefs. Some of them have 

 been raised high above sea-level. On Efate (Sandwich Island) 

 limestones, which are regarded as raised coral reefs, occur 1,500 feet 

 above sea-level (Frederick, 1913, p. 227). 



The bulk of the archipelago consists of volcanic material belonging 

 to the later eruptions. The archipelago is part of the great volcanic 

 line which passes along the Pacific border of Australasia from New 

 Guinea through the Solomon Islands to New Zealand. The New 

 Hebrides volcanoes have been in frequent eruption. Tanna, as 

 Mr. Frater remarks, is of the Strombolian type owing to its chronic 

 activity since it was seen in 1774 by Captain Cook, who was the 

 first European to visit the Archipelago. Ambrym was also then in 

 eruption. Lopevi, to the south of Ambrym (4,755 feet high), is 

 a smaller island with a regular volcanic cone. It was in eruption in 

 1864 (Purey-Cust, 1896, pp. 3-4). It is said to be the highest peak 

 in the archipelago, though according to the Sailing Directory, Pacific 

 Inlands, vol. ii, 4th ed., 1908, p. 385, Espiritu Santo rises to between 

 5,000 and 6,000 feet. 



2. Thk Volcanic History of Ambrym to 1894. 

 The eruptions on Ambrym occur at irregular intervals and include 

 explosions of paroxysmal violence. The records collected by 

 Admiral Purey-Cust (1896, pp. 5-6) indicate a disastrous eruption, 

 which, judging from the probable age of the old man who 

 remembered it, happened about 1820. Like the chief later eruptions, 

 it was at the western end of the island ; it poured lava into the sea 

 at Craig Point. Moderate activity is recorded by the officers of 

 a mission schooner, the Southern Cross, in 1870, and it is also 

 reported as having been in eruption in 1883 or 1884 (Purey-Cust, 

 1896, p. 3). Lieut. Moore of the Dart stated that in 1883 large 

 quantities of volcanic dust fell from Ambrym to the north and north- 

 west of the island, but that no lava had been discharged for some 

 years (Purey-Cust, 1896, p. 5). Mt. Marura, one of the two large 

 craters in the middle of the island, was last active in 1888. A few 

 months after it became dormant eruptions built up the crater known 

 as "Volcano ", of which the wall was breached by a lava stream, that 



