San Quintín Volcanic Field, Volcanic field in Baja California, Mexico.

The San Quintín Volcanic Field is a group of ten or eleven cinder cones along the Pacific coast of Baja California, in a shallow bay. The cones form a northern group (Media Luna and Woodford), a southern group (Basu, Riveroll, Kenton, Picacho Vizcaino, Sudoeste, and Ceniza), and the isolated Monte Mazo and Isla San Martín. Most complexes have a well-preserved scoria cone and lava apron, with 42 eruptive units visible on the ground.

The field's eruptions began in the Pleistocene and ended about 3,000 years ago. The northern cones, Media Luna and Woodford, formed 126,000–90,000 years ago; the southern group, which includes Basu, Riveroll, Kenton, Picacho Vizcaino, Sudoeste and Ceniza, formed over a longer, undetermined span. The lava shields first grew as subaqueous volcanoes that emerged as islands in a shallow bay.

The cones are named after figures and places of the region: Basu, Riveroll, Kenton, Picacho Vizcaino, Sudoeste, Ceniza, Media Luna, Woodford, Monte Mazo and Isla San Martín. Visitors reach the southern cones, including the two standing in the lagoon, by boat from the bay, while Isla San Martín lies offshore.

The cones lie along the Pacific coast about 200 km south of Ensenada, with the northern group (Media Luna, Woodford) and the isolated Isla San Martín and Monte Mazo reached from the coastal highway. Two cones stand in the shallow lagoon of the southern group, so parts of the field are seen by boat. The ground is loose scoria and lava apron, and the field sits on over a kilometre of unconsolidated sediment.

The field is the only known site of intraplate-type mafic alkalic volcanism on the Baja California peninsula, and the only source of peridotitic and granulitic xenoliths there. Its magmas came from partial melting of spinel lherzolite at unusually shallow mantle depths; the xenoliths are mostly spinel lherzolite, with harzburgites, dunites and pyroxenites making up the last 20%.