Extinct volcanoes are essentially “dead.” This happens when the tectonic plate moves away from a volcanic “hotspot” or when a subduction zone ceases to function, cutting off the source of magma. For example, Mount Kilimanjaro in Africa has three volcanic cones; while two are extinct, one is dormant. To be classified as extinct, a volcano usually must show no activity for at least 10,000 years. However, the distinction can be tricky, as some volcanoes thought to be extinct have “woken up” after millennia, technically reclassifying them as dormant.