Cinder Cone and the Fantastic Lava Beds lava and has concentric craters at its summit, which have diameters of and . Cinder Cone is comprised by five basaltic andesite and andesite lava flows, and it also has two cinder cone volcanoes, with two scoria cones, the first of which was mostly destroyed by lava flows from its base. Cinder cone volcanoes are typically monogenetic, meaning that they only undergo one eruptive period before ceasing activity forever. These eruptions often consist of the ejection of tephra, though they may also generate lava flows, which often originate from vents near the base rather than the summit of the volcanic
West Rock Ridge in faults created by the rifting apart of North America from Eurasia and Africa over a period of 20 million years. Erosion occurring between the eruptions deposited deep layers of sediment between the lava flows and around the dike, which formed sedimentary rocks. The resulting "layer cake" of igneous and sedimentary sheets was later faulted and tilted upward. Subsequent erosion wore away the weaker sedimentary layers a faster rate than the lava layers, leaving the abruptly tilted edges of the lava sheets exposed, creating the distinct linear ridge and dramatic cliff faces visible today along the Metacomet Ridge. West Rock