In the United States very few volcanoes are active at the present day, though many have become extinct only in times that are geologically recent. An eruption occurred in 1857 at Tres Virgines, in the south of California, and Lassen's Peak (Cali fornia) renewed its activity in a mild way a few years ago. The Mono Valley craters and Mount Shasta, in California, are ex tinct. The Cascade range contains numerous volcanic peaks, but only few show signs of activity. Mount Hood, in Oregon, ex hales vapour, as also does Mount Rainier in Washington. Mount St. Helens (Washington) was in eruption in 1841 and 1842; and Mount Baker (Washington), the most northern of the volcanoes connected with the Cascade range, was reported active in Volcanic activity is prominent in Alaska, along the Coast range and in the neighbouring islands. Mount Fairweather has prob ably been in recent activity, and the lofty cone of Mount Wran gell, on Copper river, is reported to have been in eruption in 1819. In the neighbourhood of Cook's Inlet there are several volcanoes, including the island of St. Augustine. Unimak Island has two volcanoes, which have supplied the natives with sulphur and obsidian. The Aleutian volcanic belt is a narrow, curved chain of islands, extending from Cook's Inlet westward for nearly 1,60o miles. It is notable that the convexity of the curve faces the ocean.
From the Aleutians the volcanic band of the Pacific changes its direction, and, passing to the peninsula of Kamtchatka, where 14 volcanoes are said to be active, turns southward and forms the festoon of the Kurile Islands. Here again the convexity of the insular arc is directed towards the ocean. This volcanic archi pelago leads on to the great islands of Japan. Of the 54 vol canoes recognized as now active or only recently extinct in Japan, the best known is the graceful cone of the sacred mountain Fuji san, but others less pretentious are far more dangerous. The great eruption of Bandai-san, about 120 m. N. of Tokio, which occurred in 1888, blew off one side of the peak called Kobandai, removing, according to Prof. Sekiya's estimate, about 2,982 million tons of material.
South of the Japanese archipelago the train of volcanoes passes through some small islands in or near the Liu Kiu group and thence onward by Formosa to the Philippines, where subterranean activity finds abundant expression in earthquakes and volcanoes. After leaving this region the linear arrangement of the eruptive centres becomes less distinctly marked, for almost every island in the Moluccas and the Sunda archipelago teems with volcanoes, solfataras and hot springs. Possibly, however, a broken zone may be traced from the Moluccas through New Guinea and thence to New Zealand, perhaps through eastern Australia.
The great volcanic district in New Zealand is situated in the northern part of North Island, memorable for the eruption of Tarawera in i886. This three-peaked mountain on the south
side of Lake Tarawera, not previously known to have been active, suddenly burst into action; a huge rift opened, and Lake Roto mahana subsided, with destruction of the famous sinter terraces.
Far to the south, on Ross Island, off South Victoria Land, in Antarctica, are the volcanoes Erebus and Terror, the former of which is active. These are often regarded as remotely related to the Pacific zone, but Dr. G. T. Prior has shown that the Antarctic volcanic rocks which he examined belonged to the Atlantic and not the Pacific type.
Within the great basin of the Pacific, imperfectly surrounded by its broken girdle of volcanoes, there is a vast number of scat tered islands and groups of islands of volcanic origin, rising from deep water, and having in many cases active craters. The most important group is the Hawaiian archipelago, where there is a chain of at least 15 large volcanic mountains—all extinct, how ever, with the exception of three in Hawaii, namely Mauna Loa, Kilauea and Hualalai; and of these Hualalai has been dormant since 1811. It is noteworthy that the two present gigantic cen tres of activity, though within 20 m. of each other, appear to be independent in their eruptivity. The volcanic regions of the Pacific are connected with those of the Indian Ocean by a grand train of islands rich in volcanoes, stretching from the west of New Guinea through the Moluccas and the Sunda Islands, where they form a band extending axially through Java and Sumatra. Here is situated the principal theatre of terrestrial vulcanicity, apparently representing an enormous fissure, or system of fissures, in the earth's crust, sweeping in a bold curve, with its convexity towards the Indian Ocean. Numerous volcanic peaks occur in the string of small islands to the east of Java—notably in Flores, Sumbawa, Lombok and Bali ; and one of the most terrific erup tions on record in any part of the world occurred in the province of Tomboro, in the island of Sumbawa, in 1815. Java contains within its small area as many as 49 great volcanic mountains— active, dormant and extinct. The most famous is Papandayang, which erupted with great suddenness and violence in 1772.
The little uninhabited island of Krakatoa in the Strait of Sunda appears to be situated at the intersection of two curved fissures, and the island itself represents part of the basal wreck of what was once a volcano of gigantic size. After two centuries of repose, a violent catastrophe occurred in 1883, whereby part of the island was blown away. This eruption and its effects were made the subject of careful study by Verbeek, Breon and Judd.