226 The Realm of Nature CHAP. 



waves. For weeks fields of floating pumice made naviga- 

 tion very difficult. The disturbance in the sea pro- 

 duced a wave more than 100 feet in height, which rushed 

 upon the neighbouring coasts, overwhelming lighthouses 

 and towns, and stranding ocean steamers in mountain 

 valleys. More than 36,000 people were washed away and 

 drowned. Part of Krakatoa was scattered as the finest 

 dust through the air and carried to every part of the Earth, 

 its presence being detected in rain, and by the magnificent 

 red sunsets ( 162) that were visible everywhere during the 

 autumn and winter of 1883 and i884. 2 



298. Distribution of Volcanoes. Volcanoes are usually 

 found in the line of great mountain chains and near the sea 

 coast. They form a " ring of fire " round the Pacific Ocean, 

 being very numerous in the Andes, and more widely spaced 

 along the plateau of Central America, the coast ranges of 

 North America, and the Aleutian Islands. Thence they 

 increase in frequency along the island festoons of Asia, and 

 come to a maximum in the Malay Archipelago and New 

 Zealand. The West Indies, many of the small Atlantic 

 islands, the Mediterranean coasts, Iceland, and Jan Meyen, 

 also contain active volcanoes, but none are known with 

 certainty in the heart of continents. The distribution of 

 active volcanoes is shown in Plate II. 



299. Earthquakes. The crust of the Earth is elastic 

 and readily transmits wave -motion. Any cause which 

 produces a local disturbance of the crust sets up a series 

 of waves, which may become apparent on the surface 

 in the quick up-and-down or to-and-fro shaking of the land 

 called an Earthquake. Earthquakes of considerable severity 

 accompany volcanic action, and are accounted for by the 

 jarring of the Earth's crust by successive explosions, but 

 they are by no means confined to volcanic regions. The 

 falling-in of underground caverns may give rise to earth- 

 quakes of slight intensity. Very severe shocks accompany 

 the elevation of land when that process takes place in 

 sudden steps of a few inches or a few feet at a time, in 

 consequence probably of the strata, subjected to the power- 

 ful stresses set up by the contracting Earth, snapping under 



