| Pioneer Seamount | |
| Depth: | 8200NaN0 |
| Height: | 19300NaN0 |
| Pushpin Map: | California |
| Summit Area: | 12.8 km (6.9 nautical miles)x12.8 km (6.9 nautical miles) |
| Coordinates: | 37.3517°N -149.1°W |
| Country: | United States |
| Type: | Seamount (underwater volcano) |
| Volcanic Group: | Central Californian seamounts |
| Age: | 10.9 to 11.1 million years |
Pioneer Seamount is an undersea mountain, or seamount, in the Pacific Ocean off the coast of central California.
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 95abbr=offNaNabbr=off off the coast[1] just southwest of San Francisco, California.[2]
The seamount is a volcano between 10.9 and 11.1 million years old. It is about 12.8abbr=offNaNabbr=off long as well as about 12.8abbr=offNaNabbr=off wide, and has a volume of about 135km3. It rises about 1930abbr=offNaNabbr=off above the surrounding ocean floor, and its peak is a minimum of 820abbr=offNaNabbr=off below the oceans surface. 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.
A wide variety of sealife lives on the seamount. 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. Pioneer operated along the United States West Coast and in the then-Territory of Alaska during her Coast and Geodetic Survey career, which lasted from 1922 to 1941.[5]