22 
PACIFIC SCIENCE, Vol. XII, January, 1958 
GENERAL DESCRIPTION AND PREVIOUS 
INVESTIGATIONS 
The Gulf of California is unique in many 
respects. Lying as it does in a predominantly 
arid region it comprises the only large evapo- 
ration basin of the Pacific Ocean. It is roughly 
rectangular in shape and lies between the 
Mexican states of Baja California to the west 
and of Sonora and Sinaloa to the east. At its 
southern end the Gulf is in open communica- 
tion with the ocean. The length of the Gulf 
is about 1400 km. and the average width 
about 150 km., giving a total surface area of 
roughly 210,000 km. 2 , if the southern boun- 
dary is taken along latitude 23°N. Between 
this latitude and a line joining Cabo San 
Lucas with Cabo Corrientes (Fig. 10) lies a 
transition region which occasionally is in- 
fluenced by Gulf water (Schott, 1935). This 
region will be called the Gulf Entrance, and 
it has a total surface area of roughly 40,000 
km. 2 
Topographically the Gulf can be divided 
into a number of basins, separated from each 
other by transverse ridges. The deepest basins 
have a maximum depth of more than 3000 
m. and a sill depth below 1500 m. (Geol. 
Soc. Amer., Mem., 1950). In the northern 
part of the Gulf isolated basins are found in 
which different hydrographic conditions pre- 
vail (Sverdrup, 1941). These basins seem to 
represent deep depressions in an otherwise 
quite narrow shelf and are completely isolated 
below 200 to 300 m. Their isolated character 
is quite sufficient to explain the hydrographic 
conditions found in them and it is not neces- 
