"Elongated Guadalupe Island lies atop a fossil oceanic ridge crest about 300 km west of Baja California. The seamount, which rises above the Pacific Ocean surface to an elevation of 1100 m, contains two shield volcanoes, the northern of which is the youngest. Chains of cinder cones constructed along fissures oriented both NW-SE and NE-SW and associated lava flows overlie both shield volcanoes. The longest of these fissures cuts across the caldera of the northern volcano and extends beyond it to the SE. Other pyroclastic cones were constructed along an arcuate fissure near the southern caldera rim. The shield volcanoes and products of the fissure eruptions form a complete alkali basaltic-to-trachytic series reflecting a transition from submarine to subaerial volcanism. The 1100-m-high northern basaltic shield volcano was considered to be of Holocene age (Medina et al. 1989). Trachytic lava domes are found within the caldera of the northern shield volcano, and together with very fresh-looking alkali basalt lava flows, form the youngest volcanic rocks on the island."  -Smithsonian Volcano Archive
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