St. Helena exists because of the St. Helena hotspot which began to produce basaltic lava about 145 million years ago when it was near the constructive plate margin of the Mid-Atlantic Ridge. The movement of the African Plate away from the hotspot has left the chain of the St. Helena seamounts, which may connect with the Cameroon Volcanic Line. St. Helena, the most south westerly point on the chain, is close to the plate margin, but the last volcanic eruptions occurred about 7 million years ago.