Rock (geology) kind of rock may thus be traced gradually merging into those of another. Hence the definitions adopted in rock names simply correspond to selected points in a continuously graduated series. Igneous rock (derived from the Latin word "igneus," meaning "of fire," from "ignis" meaning "fire)" is formed through the cooling and solidification of magma or lava. This magma may be derived from partial melts of pre-existing rocks in either a planet's mantle or crust. Typically, the melting of rocks is caused by one or more of three processes: an increase in temperature, a decrease in pressure, or a change in
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