[3] It has 1,000 times the volume of the Mississippi River and its length is 3,500 miles (3,000 nmi; 5,600 km).
This was considered unusual because the surface currents of the Pacific Ocean flow westwards at the equator, following the direction of the winds.
In 1952 Townsend Cromwell led a research party to investigate how the currents of the ocean varied as a function of depth.
The cause of the pressure gradient is at least partially the trade winds blowing from the east westward.
In non-El Niño years, the Cromwell Current is forced to the surface by underwater seamounts near the Galapagos islands (this is called upwelling.)
Upwelling, however, is a sporadic phenomenon; it fails to occur on a regular basis, and so the food supply comes and goes.