Magma production of the Anahim hotspot has shifted from more felsic to more mafic compositions in the last 3.0 million years. For instance, much of the magma created between 3.0 and 0.33 million years ago was igneous phonolite, trachyte, trachyandesite, basalt and basanite; the volcanoes built during this period are almost entirely made of these rock types. Other igneous rocks such as phonotephrite are present in smaller quantities; these occur in the Satah Mountain volcanic field. Volcanic eruptions in the last 0.33 million years have been mainly basanitic and have occurred at the youngest eruptive centre, Nazko Cone. Basanites produced by these eruptions are significantly more undersaturated than basalts from older Anahim volcanoes in the west and may indicate an eastward shift toward a deeper or less depleted mantle source. It is also possible that as the North American Plate moves over the Anahim hotspot, it underlies thinner continental crust. The overall chemistry and mineralogy of the Anahim magmas are analogous to regions of incipient continental rifting above a mantle plume.