450 THE POPULAR SCIENCE MONTHLY 



As is well known, the islands of the former are almost constantly shaken 

 by earthquakes. This region and the East Indian region, as will be 

 observed from the map, are not sharply marked off from one another. 



Along the western coast of North America, there are three earth- 

 quake regions. These are shown separately, but as a matter of fact 

 are connected by narrow strips, marking areas of more restricted seismic 

 disturbance. The central belt is thus to be connected, on the one hand, 

 with the southern belt, and, on the other, with the northern belt. The 

 most northern of these three belts lies along the coast of Alaska and 

 British Columbia; the central or California-Ecuador belt, begins in 

 California, includes all of Central America, and ends in Ecuador; the 

 southern, or Peru-Patagonia belt, follows the coast of South America 

 from Peru to Patagonia. 



Both the West Indian and the South Indian-Madagascar earthquake 

 regions extend over areas which have experienced more or less profound 

 downward crustal warping. The West Indian region, possessing defi- 

 nite features of marked structural instability, suggest the Malaysian 

 area, which latter, however, is characterized by young and growing 

 mountains, but also exhibits in certain of its parts warping of the kind 

 previously alluded to. The West Indian area is also a region of unusu- 

 ally active earthquakes which are due doubtless to a continuance of the 

 earth's movements by which the old continent of Antilla has been 

 broken up into the islands that go to make the present Archipelago. 

 The South Indian-Madagascar region is supposed to mark the site of 

 a former land mass now vanished under the Indian Ocean. This earth- 

 quake region extends from South India in a southwesterly direction to 

 the island of Mauritius and to the east of Madagascar. 



The North Atlantic may be divided into three earthquake regions — 

 of these three, one lies northeast of Iceland and parallels the coast of 

 Scandinavia. The second and largest of these three regions extends 

 from North Africa in a northward direction along and past the coasts 

 of Spain and Portugal to the west of the Bay of Biscay, and thence 

 to the west of Ireland. It was along the line of movement here de- 

 scribed that there developed the terrible Lisbon earthquake. The third 

 of these areas, which is about the size of the first and the least active of 

 the three, parallels the eastern coast of the United States and includes 

 the islands of the Bermudas. 



Some of these earthquake regions, such as the last of the eleven 

 mentioned, are notably free from violent volcanic activity; but, as we 

 have seen, even in a region containing an active volcano the most pow- 

 erful earthquakes often affect the non-volcanic districts. Thus, to re- 

 capitulate, the appalling Calabrian earthquake of 1783, though near the 

 volcanic areas of Sicily and not a great distance from Vesuvius, affected 

 a part of southern Italy where there are no volcanic rocks. The dis- 



