A team of geologists has found for the first time evidence that two ancient, continent-sized, ultrahot structures hidden beneath the Earth have shaped the planet's magnetic field for the past 265 million years. These two masses, known as large low-shear-velocity provinces (LLSVPs), are part of the catalog of the planet's most enormous and enigmatic objects. Current estimates calculate that each one is comparable in size to the African continent, although they remain buried at a depth of 2,900 kilometers.