THE SAX FRANCISCO EARTHQUAKE 



107 



it rested, and this crack often assumed formidable dimensions (Fig. 

 10) ; in fact its magnitude was found to be a convenient index of the 

 local violence of the earthquake in regions where buildings are rare. 

 Landslips from the bluffs margining the roads (Fig. 11) were also 

 very numerous, in many instances stopping traffic until repairs could 

 be made. And there were many landslides on a larger scale, the earth- 

 quake initiating movements which might otherwise have been delayed 

 for years or even centuries. Some of these landslides fell into streams, 

 dammed their waters and created temporary lakes. 



Fig. 8. Cracks caused by the Shaking of Marshy Ground. The comparatively firm 

 road embankment preserved the cracks better than the bog. 



Other disturbances of water supply were more directly connected 

 with the earthquake. At several points large volumes of water were 

 squeezed from the ground during the agitation, causing brief but 

 violent torrents, and one of these brought with it so much sand as to 

 constitute a sort of sand eruption. There are reports also that certain 

 springs have received a permanent increase in volume, a result which 

 would naturally follow from the modification of underground circula- 

 tion by the cracking of rock and earth. 



