The area is named after Ngorongoro Crater, a large volcanic caldera within the area. This volcano possesses a clearly defined summit caldera. This volcano is located at the centre of the Aso caldera. Helvellyn lies within a geological structure which is interpreted as evidence of a volcanic caldera. It is in the caldera of the Taupo Volcano. The district is within and adjacent to a Tertiary volcanic caldera. Most historical eruptions have been small explosions from Lofia cone along the northern caldera rim. These giant caldera are remnants of past eruptions. Erosion has since exposed part of the seamount in the northern sector of the Caldera. The hotspot currently lies under the Yellowstone Caldera. Mammoth Lakes lies on the edge of the Long Valley Caldera. Toba is probably the largest resurgent caldera on Earth. A collapse structure cuts into Rinjani's slopes facing the Samalas caldera. They can form prominent rounded protuberances, such as at Valles Caldera. Mazama has a few composite cones in the vicinity of the caldera.