190 INFLUENCE OF THE SEA ON ERUPTIONS. 



The kind of rock emitted varies with the district. In the Andes 

 the bulk of the volcanic rocks consists of a dark or blackish rock 

 termed Andesite, which is also seen on the southern slopes of the 

 Carpathians. It forms the Hargitta range, the Vihorlat-Gietin range, 

 and the Eperjes-Kaschau range. It is emitted from Chimborazo, 

 Cotopaxi, Antisana, Tungurahua, Popocatepetl, Colima, Teneriffe, 

 which are said never to have changed the mineral character of their 

 lavas. 



Other fissure eruptions on the Carpathians in Hungary and Tran- 

 sylvania consist of the dark volcanic rock termed Propylite. 



Trachyte is still being ejected by most of the volcanoes of Central 

 America. It forms the base of Etna and the older rocks of the 

 Campi Phlegraei. It occurs in the Lower Rhine and Central France ; 

 and circles round the east of the Washoe Mountains. 



Rhyolite, in Hungary, skirts the lower part of the Andesite 

 ranges, and forms the Tokay Mountains. Yast sheets occur on the 

 east of the Sierra Nevada. 



Professor Joseph Le Conte states that the lava- floods of the 

 Sierras commence in Middle California as immense but separate 

 lava streams. In Northern California they become an almost con- 

 tinuous flood, which in Oregon is 2000 feet thick, and universally 

 spread. It streams away to the north through Washington Territory, 

 and on into British Columbia for an unknown distance. This lava 

 inundation has a length of 700 to 800 miles; the stream is 80 to 100 

 miles broad, and where cut through by the Columbia River is 2000 

 to 3000 feet thick. It is one of the most remarkable results of fissure 

 eruptions that is known. 



Nearness of Volcanoes to the Sea. If we refer to a map record- 

 ing the distribution of active volcanoes, such as that given by 

 Professor Karl Fuchs, 1 it will be observed that nearly all the volcanic 

 regions of the earth are remarkable for their linear extension, and 

 in this we may see evidence of their arrangement along fissures 

 of great magnitude. And secondly, it may be noticed that with few 

 exceptions they are situate either in oceanic islands or comparatively 

 near to the sea. And when this distribution is compared with that 

 of the great regions of extinct volcanoes, which are for the most part 

 in the interior of continents, and far removed from the sea, we have 

 strong presumptive evidence that volcanoes need for their activity 

 more water than can usually be furnished from a sub-aerial source ; 

 for it would seem that as land is uplifted, and the volcano removed 

 from the sea, its eruptive power usually disappears. But we are 

 further compelled, by the theory of fissure eruptions, to conclude 

 that the situation near the sea is not due to the action of water alone, 

 but is a consequence of the ways in which the rocks, which undergo 

 compression so as to rise in island chains and mountain ranges, are 

 ever developing new fractures, parallel to the direction of their 

 upheaval; and while this cause may develop new heat, and give 

 access for new supplies of water to the region which is heated, it 

 1 " Vulkane und Erdbeben," 1875. 



