112 IGNEOUS AGENCIES. 



especially those of the explosive type, are always preceded and accom- 

 panied by earthquakes. 2. Earthquake-shocks which have continued to 

 trouble a particular region for a long time, often suddenly cease when 

 an outburst takes place in a neighboring volcano, showing that the 

 latter are safety-vents for the interior forces which produce earthquakes. 

 Also, the sudden cessation of accustomed volcanic activity will often 

 bring on earthquakes. Thus, when the wreath of smoke disappears 

 from Cotopaxi, the inhabitants of Quito expect earthquakes. During 

 the great Calabrian earthquakes of 1783, Stromboli, for the first time in 

 the memory of man, ceased erupting. The great earthquake which de- 

 stroyed Eiobamba in 1797, and in which 40,000 persons perished, took 

 place immediately after the stopping of activity in a neighboring vol- 

 cano. The earthquake-shocks which destroyed Caracas in 1812 ceased 

 as soon as St. Vincent, 500 miles distant, commenced erupting. 3. Ex- 

 amination of Prof. Mallet's earthquake-map shows that the distribution 

 of earthquake-centers is much the same as that of volcanoes already 

 given (page 88). It may be regarded as almost certain, therefore, that 

 the forces which generate earthquakes are closely allied, if not identical, 

 with those which produce volcanic eruptions. 



Again, the connection of earthquakes with bodily movements of 

 great areas of the earth's crust, by elevation or depression, is equally 

 close. In 1835, after a great earthquake, which shook the coast of 

 South America over an area of 600,000 square miles, the whole coast- 

 line of Chili and Patagonia was found elevated from two to ten feet 

 above sea-level. Again, in 1822, after a similar earthquake in the same 

 region, the coast-line was found elevated from two to seven feet. Now, 

 in this very region, old beach-marks, 100 feet to 1,300 feet above the 

 sea-level, and extending 1,200 miles along the coast on each side of the 

 southern end of this continent, plainly show that, in very recent geo- 

 logical times, the whole southern end of South America has been bodily 

 raised out of the sea to that extent. It is impossible to doubt that the 

 force which produced this continental elevation was also the cause of 

 the accompanying earthquakes. Again, in 1819, after a severe earth- 

 quake, which shook the whole region about the mouth of the Indus, a 

 large tract of land of 2,000 square miles was sunk and became a salt 

 lagoon ; while another area, fifty miles long and ten to sixteen miles 

 wide, was elevated ten feet. In commemoration of this wonderful 

 event, the raised portion was called Ullah Bund, or the Mound of God. 

 Again, in 1811, a severe earthquake shook the valley of the Missis- 

 sippi. In the region about the mouth of the Ohio, where it was se- 

 verest, large tracts of land were sunk bodily several feet below their for- 

 mer level, and have been covered with water ever since. It is now 

 called the " Sunk Country." The Inyo earthquake of 1872 was ac- 

 companied by a fissure of forty miles in length and a slip or fault of 



