[4] Other volcanic centres in the neighbourhood are Tres Virgenes and El Aguajito (first identified as "Santa Ana caldera" in 1984),[5] west of La Reforma.

[6] Offshore east of La Reforma lies the Virgenes High, a submarine elevated platform,[7] probably associated with basaltic intrusions at the intersection of two volcanic ridges.

Isla Tortuga, a volcanic island formed on a fracture zone, is also to the east of La Reforma.

[8] The La Reforma caldera has a diameter of 10 kilometres (6.2 mi),[2] and the height of its rim ranges from 100 to 500 metres (330 to 1,640 ft).

[9] It is a semicircular structure around Cabo Virgenes, which reaches the Gulf of California at La Reforma in the northwest and Punta Las Cuevas in the southeast.

[9] Alternative theories are that La Reforma is a dome which was eroded to form a circular pattern or a set of tectonic blocks.

Although the dome was thought to be formed by the older Comondú volcanics, it appears to be a product of La Reforma activity.

[16] Interaction between the San Andreas Fault and the East Pacific Rise triggered the formation of a transform boundary in the gulf 3.5 million years ago.

[18] As part of this movement of the Earth's tectonic plates, the Santa Rosalía Basin formed through crustal extension and was filled by a number of Miocene-Pleistocene layers of rock, some of which are exposed in La Reforma.

[15] Younger basement rocks comprise Miocene marine sediments and volcanics pertaining to the Comondú Group.

[3] This is consistent with the geochemistry of nearby Tres Virgenes, although one pyroclastic flow at La Reforma was considered peralkaline.

[10] Volcanic activity at La Reforma occurred between 1.6 and 1.4 million years ago,[29] and at least four ignimbrites have been found there.

[28] Basaltic cones[2] which erupted 600,000 years ago[10] on the caldera's flanks despite their location are not part of the La Reforma volcano; like Isla Tortuga and Tres Virgenes, they are controlled by the tectonic processes that accompanied the rifting of the Sea of Cortez.

A combination between this doming and uplift of the surrounding land of the Baja California peninsula raised Pleistocene sea deposits to over 300 metres (980 ft).