THE EARTH MOVEMENT ON THE FAULT OF APRIL 18, 1906. 81 
Berkeley, and arrangements were made for field examinations by naturalists. On Octo- 
ber 26 Professor William E. Ritter and Mr. E. L. Michael went to Bodega Bay, where 
they spent several days, and at the same time Profs. Chas. A. Kofoid, H. B. Torrey, 
and R. 8. Holway visited various points on the shores of Tomales Bay and Tomales 
Peninsula. On November 24 and 25 Professor Kofoid accompanied me to Bolinas for 
the purpose of gathering such evidence as might be afforded by marine invertebrates. 
On March 8-9, 1907, Professor Holway and I visited Bolinas, and on April 9-10 I was 
accompanied by Professor Willis L. Jepson in the same locality. On April 18 I made an 
examination of the Papermill Creek delta at the head of Tomales Bay, and on April 22 
visited the sand-spit separating Bolinas Lagoon from the ocean. The results of these 
various excursions are summarized below, and reports by Professors Ritter, Kofoid, 
Holway, and Jepson are appended. 
About Bolinas Lagoon. — In presenting the evidence as to land-movements in the 
vicinity of Bolinas Lagoon, first place will be given to testimony of residents, and this 
again will be classified according to locality, beginning with the features west of the 
fault-trace. 
Dr. Southworth has lived in Bolinas several years, and his activities during that period 
have led him into almost continuous observation of the coast and the tide. There is a 
clam patch on the ocean front between Bolinas 
and Duxbury reef (see fig. 28 and plate 56s), 
to which he has frequently resorted at suitable 
stages of the tide. It has been his custom 
regularly to consult the tide tables to ascertain 
whether the water stage would expose the 
patch. He reports that before the earthquake 
there were ordinarily about four low tides in 
the month, occurring by daylight, during which 

Pepper |. 
clams might be obtained, and that since the ' Me Kenton | 
earthquake twenty or more days are available. : 
He infers that the land was lifted at least a Z pire 
. ° +Clam Patch , 
foot, possibly more, at the time of the earth- OCEAN Scale 

quake. He states also that about 5 miles to 
the northwest there is a tract, exposed only at 
low tide, where abalones are abundant, and 
that people living near there have found them much more accessible since the earth- 
quake than before. In Bolinas Lagoon a channel between Pepper Island and the 
mainland is not now navigable at certain tide stages which formerly made it entirely 
navigable. 
Dr. Gleason, owner and master of a vessel plying between Bolinas and San Francisco, 
states that formerly it was his custom to turn his vessel in the channel between Pepper 
Island and the west end of the sand-spit, but that after the earthquake he found the place 
too shoal, so that, after a number of trials in which his vessel was grounded, he has 
adopted the practice of entering the lagoon stern first, to avoid the turn. 
The following observations pertain to localities east of the fault. A road which skirts 
the northeast shore of the lagoon is not altogether on the mainland, but in places follows 
the strand between high and low water, and if it is used at high water the horses must 
ford. Dr. Southworth states that since the earthquake these fords have become more 
difficult, so that to pass them safely or comfortably they must be reached when the 
tide, as indicated by the tables, is lower than was formerly necessary. Mr. B. C. Morse, 
however, who lives on the mainland east of McKennan Island, and who ordinarily crosses 
the lagoon to Bolinas every day, states that he has noticed no change in the relation of 
G 
Fia. 28. — Sketch map of Bolinas Lagoon. Broken 
lines show fault-trace and its branches. 
