Show EARTHQUAKE EARTH T L CAUSES USES TILE QUAKE QUAtE Nobody knows It is ono one of ot th Ui thc toward which much study stud ha he hM tho the thin S 'S been directed but ono of ot which no fellow tellow has found out Probably ably the cyclopedia publishers ha hav employed tho best beet authorities on a aJ aU subjects handled and here Is what tho th foremost writer in that service ha has said Bald As earthquakes aro are frequently connected connected con con- with I h tho the eruptions of volcanoes J and are common in volcanic regions region many nany observers believe the they are volcanic volcanic volcanic vol vol- canic phenomena This view was firs first expressed nearly two thousand years ago go by Plin Pliny and during the first hallof hall half nineteenth century was held bj br ot of the many geologists Including von on Hum Hum- boldt From the fact tact however that thai many earthquakes about the Mediterranean In California and el volcanic are not accompanied by an any activity i and since elude any heavy y shock or ox blow blo within the tho earths earth's crust would be propagated b by impulses t. t to t the surface causing c an earthquake itIs it itis that earthquakes earthquakes earthquakes earth earth- is now generally quakes aro due to a variety of or causes It is plain that some somo earthquakes ar are that due to the explosions of steam are arc the chief characteristics of violent 1 c eruptions Thus the tho terrific t that r V tho tim C lt r part pai I J.- J. land of ot talato In as blent earthquake c. c Of ot a n. frequently precede volI voIr voland vol- vol huyts and cease when the he thet is r I t t Again it Is possible 1 regions of or present or recent Reactivity lie when no volcanic volcan c out out- or follows an al anI C I I the latter may ha have e been sed by br movements of ot molten rock ep underground The sudden ex- ex of ot such rock if it pressure were by b the opening of ot some us- us ure as in tho the formation oC or dikes In earthquake severe ht cause a a. remote from volcanoes It is possible that earthquakes aro caused by the same stresses on the earths earth's crust partly duo due to secular contraction contraction tion that tilt and fold rock strata into mountains The strain to which rocks aro thus subjected when Bud and suddenly denly enly relieved by bj- the thc rocks roel giving way produce many earthquakes of or slight earthquakes In fact act tho Himalayas Him Him- Himalayas in the Alps J. J frequent occurrence Oregon Oregon indi indicate as and in southern cate that mountain building is still in progress l The e seismic zone that enCircles encircles en en- circles the tho earth therefore is simply earths earth's a a. zono zone of ot weakness in the tho crust within which movements aro frequent Earthquakes in regions remote from any volcano olea have usual usually when care caie- carefully line lino fully lully full studied been een traced to some Boma of ot rock weakness as aa a fault nulL Such accompanying ac an- lc- lc earthquakes are arc simply implY phenomena companying rock movement that may ma in lii time greatly modify the earths earth's sur cur face tace The frightful loss of life Ufe caused by byI I omo bomo violent earthquakes has led to tl their geological Importance being exaggerate ex ex- fan any earthquakes n Japan are believed to be caused by bya a accumulations of oC submarine submarino sediment sliding down tho the deep slope siope of or the con- con shelf shelt just east cast of Japan |