Magma 50%, because eventually the melted rock mass becomes a crystal-and-melt mush that can then ascend "en masse" as a diapir, which may then cause further decompression melting. The degree of partial melting is critical for determining what type of magma is produced. The degree of partial melting required to form a melt can be estimated by considering the relative enrichment of incompatible elements versus compatible elements. Incompatible elements commonly include potassium, barium, caesium, and rubidium. Rock types produced by small degrees of partial melting in the Earth's mantle are typically alkaline (Ca, Na), potassic (K) and/or peralkaline (high aluminium to
West Crater imply that they resulted from the same movement of magma and were possibly fed by the same magma chambers. The lava dome likely formed before the lava flows erupted, suggested by its steep western side and the appearance of rock from the dome on the western lava flow. The dome's deep depression may have formed when the dome's top collapsed as lava moved out of the volcano during the eruption of the two flows. The human population within of West Crater is slightly more than 500 people, but more than 14,000 people live within of the volcano, and more than