Pioneer Seamount is located at 37° 21.1' North Latitude, 123° 26.1' West Longitude,[1] at the base of the continental slope[2] of North America about 95 kilometers (59 miles) off the coast[1] just southwest of San Francisco, California.

Samples from the seamount consist of highly vesicular alkalic basalt, hawaiite, and mugearite.

[3] The seamount and its volcano once extended above the sea surface, but eroded and sank as the seamount and the seabed at its base were carried further away from the spreading center from which it presumably originated.

Corals dominate in deeper areas and sponges in its shallower parts.

[4] Pioneer Seamount was named for USC&GS Pioneer, the first of three survey ships of the United States Coast and Geodetic Survey to bear the name.