THE EARTHQUAKE RIFT OF 1006 



2 93 



Tojiales, Marin County. The North Shore Railroad and the earthquake rift. 



will be naturally renewed. A faulted rock bed will be cemented in 

 the course of ages of pressure and of cementation. 



The most interesting of these breaks in California is that recorded 

 as the Portola-Tomales fault. Its course can be plainly traced on the 

 relief map. It enters the shore near the mouth of Alder Creek and 

 near the low headland called Point Arena, in Mendocino County on the 

 north, and runs to Chittenden, on the Pajaro River, in Monterey 

 County, on the south. The line is almost perfectly straight, and its 

 course and direction can be determined by placing a ruler on the map, 

 using the line of Tomales Bay as an axis. This long, narrow, straight 

 inlet is a resultant of past earthquakes, probably beginning in Tertiary 

 times. It is bounded on the west by mountains which have their origin 

 in some ancient upward thrust of the walls on the west side of the 

 ancient fault. 



On the eighteenth of April the trouble began in the sea. Just 

 where, we may find out later. We know that the center is in the sea, 

 because where the rift enters the land it was broader and its effects 

 more violent than at any other point along its extent. As the rift can 

 be traced for 192 miles across the land to the southward from Point 

 Arena, it is safe to say that it goes as far to the northward under the 

 sea. A steamer crossing it the moment of the earthquake, off Men- 

 docino, ninety miles to the northward of Point Arena, bears witness 

 to this fact. The captain thought that he had struck a raft of logs, 

 so fierce and hard were the shocks of the waves in the water.. The 

 movements were short, quick and violent, not forming a tidal wave, 

 but a strange choppy sea. For the time being all rollers and surf were 

 broken up. Off the bold headland of Cape Mendocino is a deep sub- 



