PEALE.] THEEMAL SPRINGS EFFECTS OF EARTHQUAKES. 363 



poured out in Pliocene time. On the island of Pantellaria hot vapors 

 rise from the rocks, and yet there has been no eruption within historic 

 time. 



The presence of warm and hot springs is usually, and with apparent 

 good reason, considered as an evidence of the waning of volcanic activ- 

 ity, and yet they may presage eruptions as in the case of Monte Nuovo, 

 where hot water and steam escaped before the elevation of the mount- 

 ain. 



In Hungary, siliceous sinters and travertine have been formed pre- 

 vious to the pouring out of lava, and in Iceland the two are contempo- 

 raneous, many volcanic eruptions having occurred since the geysers 

 first began to deposit their siliceous sinters. Still, in many places the 

 only i)resent sign of igneous activity is to be noted in the warm and hot 

 springs, and they represent one of the last stages in the cycle of changes 

 through which those portions of the globe subjected to volcanic action 

 are destined to pass, and, eventually, even the sxorings will lose their 

 heat.* 



THE EFFECTS OF EARTHQUAKES. 



The effect of earthquakes upon thermal springs is a proof of their inti- 

 mate connection with volcanic action. In the first place, as we have 

 already intimated, the existence of fissures and cracks in the earth's 

 surface, by whatever means they have been formed, are efficient agents 

 in causing hot springs by allowing meteoric waters to penetrate to 

 great depths, and affording them afterwards free access to the surface. 

 Earthquakes, as all know, occupy the very first place in the produc- 

 tion of fractures of far-reaching extent, both geographically and geo- 

 gnostically. 



The great Lisbon earthquake of 1755, which was so far-reaching in its 

 effects that, according to Humboldt, an area equal to more than four 

 times that of Europe was shaken by its vibrations, affected numerous 

 springs in widely- separated areas. Those of Teplitz, in Germany, were 

 muddy dm ing the earthquake, then disappeared for a short time, and 

 afterwards flowedmore copiously than before. At Clifton, in England, the 

 springs became turbid, and in France, at Luchon, the '^Source de la 

 Ueine''^ was changed from a tepid spring to one having a temperature 

 of 122° F., which has been retained. 



An earthquake in 1638 caused the breaking out of the thermal springs 

 of St. Eufemia, in Terra di Amato, and in 1783 (the year of the great 

 Calabria earthquake) they became hotter and gave out a greater quan- 

 tity of water. In 1600 an earthquake made some of the springs at Bag- 

 neres de Bigorre suddenlj^ cold. In 1770 hot springs broke out on San 

 Domingo during an earthquake, but they afterwards ceased to flow. 



During the earthquake of 1760, at Cumaua, in Venezuela, sulphur- 

 water, with sand and mud, was frequently thrown from wells to a height 

 of 30 feet. 



In Iceland, before the eruption of Skai^ter Jokul in 1783, many springs 

 were diminished, and in 1784, during an earthquake, according to Sir John 



* The ruins of former hot springs localities are found in many parts of the Western 

 United States, and I hav^ desci-ibed one in the rciiort of the survey for 1871, page 1P2, 

 and in the Yellowstone National Park individual springs die out. In Iceland, siliceous 

 deposits are found where thesprings are extinct, and according to Bischof (Treatise ou 

 Internal Heat of the Globe, p. 230), in the Sneefickl Sysael in Iceland, a spring is found 

 which is now cold, but once was hot, as its deposits show. 



