Initial volcanism of the NCVP 20 million years ago was sporadic, producing small volumes of material. The eruption rate increased markedly to around per year when volcanism began at Level Mountain 14.9 million years ago as part of the shield-building stage. This stage of volcanism ended 6.9 million years ago with completion of the basal shield volcano. A second stage of volcanism occurred at Level Mountain between 7.1 and 5.3 million years ago to create the stratovolcano cap. The rate of volcanism in the NCVP during this stage of activity increased again to per year. Dome-forming eruptions were dominant during the third eruptive stage 4.5 to 2.5 million years ago during which a magmatic lull appears to have been present throughout the NCVP. A fourth and final stage of volcanism at Level Mountain commenced in the last 2.5 million years with the formation of minor volcanic cones and lava flows. The NCVP volcanism rate has since remained relatively constant at per year with volcanism of the final stage having continued possibly in the last 10,000 years. Modern NCVP volcanism rates are much less than those estimated for Hawaii or the Cascade Volcanic Arc of western North America.